KOFORIDUA TECHNICAL UNIVERSITY FACULTY OF APPLIED SCIENCE AND TECHNOLOGY DEPARTMENT OF FOOD AND POSTHARVEST TECHNOLOGY A RESEARCH ON THE DEVELOPMENT OF LOW FAT ICE CREAM FLAVOURED WITH AVOCADO (PERSEA AMERICANA) FRUIT PULP. BY OPARE JEMIMA ADUBEA (04/2018/3951D) A PROJECT WORK SUBMITTED TO THE DEPARTMENT OF FOOD AND POSTHARVEST TECHNOLOGY, KOFORIDUA TECHNICAL UNIVERSITY IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF HIGHER NATIONAL DIPLOMA IN FOOD TECHNOLOGY. DECEMBER, 2021 STUDENTS' DECLARATION I hereby declare that this project work is the outcome of my own research and that no part has been presented for the award of any other certificate in this University or elsewhere. OPARE JEMIMA ADUBEA (04/2018/3951D) …………………………. …………………………. DATE SIGNATURE i SUPERVISOR’S CERTIFICATION I hereby certify that this project work was supervised in accordance with the University’s guidelines for supervision of project work. MS. DHAILLY ARABA ARKORFUL …………………………. (SUPERVISOR) DATE ii …………………………. SIGNATURE ACKNOWLEDGEMENTS My most sincere gratitude goes to God Almighty who has brought me this far in my academic career. I give Him all the thanks for the wisdom and knowledge in putting these scripts together for the successful completion of this project work. My hearty gratitude also goes to my project supervisor Ms. Dhailly Araba Arkorful for her unending devotion, time and attention towards me, that greatly helped me in accomplishing this work. My gratitude also goes to my family and love ones for their support, both financially, morally and their advice during my trying times in the course of this project work. It is my prayer that God meets you all at your various points of need. iii ABSTRACT Consumer preferences towards plant-based foods have shifted significantly due to sustainable and healthy reasons. Dairy products consist of high saturated fatty acid (SFA) and overconsumption of SFA could lead to cardiovascular diseases. Avocado contains high levels of fat dominated by monounsaturated fatty acid (MUFA) and phytosterol that have the potential as plant-based fat to substitute dairy fat in ice cream. The objective of this study was to analyze the physiochemical, rheological and sensorial properties of ice cream substituted with different concentrations of avocado paste ranging from 20%, 30%, 40%, 50% and 60% respectively against dairy fat to produce non-dairy fat ice cream. The physiochemical properties and total fat were determined. Sensorial quality and hedonic attributes of the ice cream were investigated using 30 semi-trained panelists. There were significant differences (p<0.05) for some parameters of the ice cream substituted with avocado paste while the sensorial attributes for taste, colour, flavour, aroma and overall acceptance also had some significant differences (p<0.05). The addition of 20% (T2) of the avocado paste was the most preferred amongst the panelists. Avocado could provide a potential substitution for dairy fat in ice cream. iv TABLE OF CONTENTS CONTENT PAGES STUDENTS' DECLARATION ....................................................................................................... i SUPERVISOR’S CERTIFICATION ............................................................................................. ii ACKNOWLEDGEMENTS ........................................................................................................... iii ABSTRACT ................................................................................................................................... iv TABLE OF CONTENTS ................................................................................................................ v LIST OF TABLES ....................................................................................................................... viii LIST OF FIGURES ....................................................................................................................... ix CHAPTER ONE ........................................................................................................................... 1 1.0 INTRODUCTION .................................................................................................................... 1 1.1 BACKGROUND OF STUDY .................................................................................................. 1 1.2 PROBLEM STATEMENT ....................................................................................................... 3 1.3 JUSTIFICATION ..................................................................................................................... 4 1.4 SCOPE OF STUDY.................................................................................................................. 4 1.5 OBJECTIVE OF STUDY ......................................................................................................... 4 1.6 ORGANIZATION OF STUDY ................................................................................................ 5 CHAPTER TWO .......................................................................................................................... 6 LITERATURE REVIEW ............................................................................................................ 6 2.0 INTRODUCTION .................................................................................................................... 6 2.1 LITERATURE REVIEW ON LOW FAT ICE CREAM USING AVOCADO FRUIT PULP 6 CHAPTER THREE .................................................................................................................... 20 RESEARCH METHODOLOGY .............................................................................................. 20 3.0 MATERIALS .......................................................................................................................... 20 3.1 STUDY LOCATION .............................................................................................................. 20 3.2 PREPARATION OF SAMPLES ............................................................................................ 20 3.2.1 Preparation of Avocado Fruit Pulp ...................................................................................... 21 v 3.2.2 Preparation of Ice cream; ..................................................................................................... 21 3.3 PROXIMATE AND PHYSIOCHEMICAL ANALYSIS ON AVOCADO ICE CREAM. ... 29 3.3.1 Moisture Content Determination ......................................................................................... 29 3.3.2 Ash Content Determination ................................................................................................. 30 3.3.3 Crude Protein Determination ............................................................................................... 30 3.3.5 Crude Fat Determination...................................................................................................... 31 3.3.6 Free Fatty Acid Determination. ........................................................................................... 32 3.3.7 Determination Of pH ........................................................................................................... 32 3.4 Determination of Total Soluble Solids. .................................................................................. 32 3.5 Overrun ................................................................................................................................... 33 3.6 Melting Rate............................................................................................................................ 33 CHAPTER FOUR ....................................................................................................................... 37 RESULTS AND DISCUSSION ................................................................................................. 37 4.0 INTRODUCTION .................................................................................................................. 37 4.1 CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY OF THE AVOCADO FRUIT PULP. ............................................................................................................................... 37 4.1.1 SENSORY EVALUATION ................................................................................................ 38 4.2. PHYSIOCHEMICAL PROPERTIES OF THE VARIOUS ICE CREAM SAMPLES ........ 46 4.2.1 pH......................................................................................................................................... 47 4.3 Total Soluble Solids ................................................................................................................ 48 4.4 NUTRITIONAL COMPOSITION OF THE VARIOUS ICE CREAM SAMPLES .............. 49 4.4.1 MOISTURE CONTENT ..................................................................................................... 49 4.5 TOTAL FAT DETERMINATION ......................................................................................... 51 4.5.1 FREE FATTY ACID DETERMINATION ......................................................................... 52 4.6 ANTIOXIDANT ACTIVITY ................................................................................................. 54 4.6.1 PROTEIN DETERMINATION........................................................................................... 55 4.7 PHYSIOCHEMICAL PROPERTIES (OVERRUN AND MELTING RATE) OF THE VARIOUS ICE CREAM SAMPLE. ............................................................................................ 56 4.8 MELTING RATE ................................................................................................................... 58 vi CHAPTER FIVE ........................................................................................................................ 60 5.0 CONCLUSION AND RECOMMENDATION ...................................................................... 60 5.1 RECOMMENDATION .......................................................................................................... 61 REFERENCES ............................................................................................................................ 62 vii LIST OF TABLES TABLE PAGES Table 3.1 Specifications of different ice cream mixes. ................................................................ 20 Table 4.1 Chemical composition and antioxidant activity of Avocado ....................................... 37 Table 4.2 Results of samples in relation to the attribute taste ..................................................... 38 Table 4.3 Results of samples in relation to the attribute colour................................................... 40 Table 4.4 Results of samples in relation to the attribute flavour ................................................. 41 Table 4.5 Results of samples in relation to the attribute aroma ................................................... 42 Table 4.6 Results of samples in relation to the attribute mouthfeel............................................. 44 Table 4.7 Results of samples in relation to the overall acceptability........................................... 45 Table 4.8 Physiochemical properties (pH and TSS) of the various ice cream samples............... 46 Table 4.9 Nutritional composition (moisture, total fat%, FFA, Antioxidant activity and protein%) ....................................................................................................................................................... 49 Table 4.10 Overrun percentage. ................................................................................................... 56 viii LIST OF FIGURES FIGURES PAGES Figure 4.1 Antioxidant capacity standard calibration curve. ........................................................ 54 Figure 4.2 Results of melting rate. ................................................................................................ 58 ix CHAPTER ONE 1.0 INTRODUCTION This chapter is the introduction part of the study that entails the background of the study, problem statement, aims and objectives of the study, research methodology, research questions, scope of study, organization of study and justification. 1.1 BACKGROUND OF STUDY Ice cream is a complex colloidal system, containing fat globules, air bubbles and ice crystals dispersion/solution of proteins, salts, polysaccharide sugars and different flavors. Milk fat has been recognized as a critical factor for the formation and support of structural characteristics of ice cream as well as for the formation and support of structural characteristics of ice cream as well as for the perceived texture of quality. The avocado (Persea Americana), a tree likely originated from south-central Mexico, is classified as a member of the flowering plant family Lauraceae (Royal Botanic Gardens et al., 2010) The fruits of the plant also called an avocado (or avocado pear or alligator pear), is botanically a large berry containing a single large seed (Wegier et al., 2017). The avocado may be originated in southern Mexico but was cultivated from the Rio Grande to central Peru long before the arrival of the Europeans. Thereafter, it was carried not only to West Indies, but also to nearly all parts of the tropical and subtropical world with suitable environmental conditions. Now avocado is grown commercially in most parts of the world. (Morton, 1987). Ghanaian avocados range in size, shape, color and flavor thanks to a large gene pool in the country. There are many local varieties and hybrids that offer unique fruit and fruiting qualities, from early bearing to late season, and from green-skinned to dark purple-black fruit at maturity. The peel may be thick and pebbled, as found in the Guatemalan race of avocados, thin and delicate, typical of 1 the Mexican race, or smooth, leathery, and thin-to-medium in thickness, characteristics of the West Indian race. Hass is the most common type of avocado that is available in all parts of Ghana and even the world at large. Ghanaian avocados vary from pear-shaped to rounded, and can weigh as much as a pound or more. The pale green or yellow flesh can be more watery, fibrous, dry or buttery, depending on the variety and oil content. The flavor of avocado varies from mild to rih, and offers hints of sweetness or nuttiness. Ghanaian avocados are available year-round in the local markets (Tobón et al., 2017). Avocados are most well known for being a good source of mono saturated, second only to olives amongst other fruits and vegetables so it is the most suitable fruit that can be used for mayonnaise unlike the other forms of mayonnaise on the local markets. Avocado can be used in its raw state or cooked by the application of a little heat although avocados are mostly used or eaten in its raw state. Good nutrition is one of the keys to a healthy life. You can improve your health by keeping a balance diet. It is important to eat foods that contain vitamins and minerals because it all contributes to the fitness of the human immune system. In Ghana, ice cream made from avocado fruit pulp is not as common and well known as compared to the regular ice creams on the local market, it is very healthy, nutritious and easy to make in our various homes as compared to other forms of ice creams. Avocado ice cream is made from real avocados, which gives it a brilliant green color. Avocado ice cream has the highest source of protein of all fruits, and have more potassium than other plant-base crops. They also contain dietary fiber, folate, vitamin C, vitamin K, and vitamin E. They are considered a ‘nutrient booster’ because they enable the body to absorb more fat-soluble nutrient. Avocado ice cream contains a good source of monounsaturated fat (most of which are oleic acid) which is good for your heart, fight inflammation, and may have anticancer properties and can help absorb other fat-soluble nutrients (Lauren, 2019). Furthermore, avocado is 2 full of fiber, which is an important nutrient lacking in most Western diets. Studies have shown that people who consume avocado tend to weigh less, perhaps due to the fruits’ high content of fiber and healthy fat as well as its low glycemic index (Lauren, 2019). It also contains antioxidants that are good for your eyes and brain, such as lutein and zeaxanthin. These antioxidants may lower your risk of metabolic syndrome. Although avocado ice cream has many nutritional benefits to the human system, it has its disadvantages when it comes to its shelf life and color. The one caveat to making this avocado ice cream is that, avocado undergo enzymatic browning when exposed to oxygen and this tends to give an undesirable color to the blend (Christous et al., 2009). Almost everyone can benefit from cutting back on unhealthy fat. If you currently eat many of the regular ice creams, commit to cutting back and changing your habits by adopting to the use of avocado ice cream that contains more healthy fats and other nutrients that is good for the body’s immune system (Baars et al., 2004). 1.2 PROBLEM STATEMENT Ice cream is high in sugar and fat, which makes up the majority of its carbohydrate and fat content (Bower et al.,2004). The consumption of too much sugar and fat has contributed to health problems such as weight gain, cavities and increased levels of blood triglycerides, another unhealthy type of fat (Ranganathan et al., 2004). To lower the risk for high cholesterol and sugar-related problems, there has been the need to produce a low-fat, low-sugar ice cream making use of the avocado fruit pulp in order to solve health problems associated with the consumption of a full fat ice cream (Christous et al., 2009). 3 1.3 JUSTIFICATION Using avocado ice cream ensures that the cream is filled with what is considered good, healthy fats (monosaturated fats) (Bower et al., 2004). It is also high in oleic acid (an omega-9 fatty acid), which is taught to have anti-inflammatory and immune-boosting properties (Brian, 2014). Also, storing the ice cream in a container with a tight fitting lid prevents oxygen ingression. Ice creams cannot be stored under normal room temperature so it must be kept frozen (Owni et al., 2009). In order to maintain this physical property, avocado ice cream must be stored in a freezer at an ambient temperature in relation to time (Dello et al., 2004). 1.4 SCOPE OF STUDY Determination of the nutritional composition of the avocado ice cream. Consumer acceptability of avocado ice cream using different percentage of avocado fruit pulp. 1.5 OBJECTIVE OF STUDY MAIN OBJECTIVE The main objective of this work is to produce a low fat ice cream with the use of avocado fruit pulp. SPECIFIC OBJECTIVES The specific objectives are outlined below; To produce low fat ice cream using avocado fruit pulp in different proportions (20, 30, 40, 50 and 60%). 4 To analyze the physiochemical properties of the ice cream using different proportions of the avocado fruit pulp. To analyze the nutritional composition of the ice cream produce. To analyze the sensory properties of the ice cream produce. 1.6 ORGANIZATION OF STUDY The study has been organized into five chapters. The first chapter gives a background of the study, problem statement, main aim and specific objectives of the study. The second chapter takes care of the literature review related to the research topic under study. Chapter three explains how the study was conducted and the method employed. It comprises of the research design, equipment used, and data collection procedure as well as data analysis. Finally, chapter four and five presents the findings of the study that is used to draw conclusions and recommendations on the research topic under study. 5 CHAPTER TWO LITERATURE REVIEW 2.0 INTRODUCTION This chapter contains the literature review on avocado ice cream, materials and method which would be adopted to conduct the research. 2.1 LITERATURE REVIEW ON LOW FAT ICE CREAM USING AVOCADO FRUIT PULP Consumer preferences towards plant-based food have shifted significantly due to sustainable and healthy reasons (Ranganathan, 2016). Dairy products consist of high Saturated Fatty Acids (SFA) and overconsumption of SFA could lead to cardiovascular diseases. The preference towards plantbased diets has significantly increased (Granato et al., 2010), with the rise of millennial generation who are increasingly adopting vegan and free-lactose diets (Flavera et al., 2008). Ice cream is a complex colloidal system, containing fat globules, air bubbles and ice cream crystals dispersed in a freeze-concentrated dispersion/solution of proteins, salts, polysaccharides, sugars and different flavours. Milk fat has been recognized as a critical factor for the formation and support of structural characteristics of ice cream as well as for the perceived textural quality example, lubrication of tongue, richness of mouth feel, enhancement of creaminess, thickness and flavor perception (Turgut and Cakmacki, 2009). However, several chronic diseases found to be correlated with fat rich foods such as obesity, cardiovascular diseases and cancer (Fenelon and Guinee, 2000). Therefore, there is a growing demand for low fat products which retain the desirable characteristics of the full- fat product (Romeih et al., 2002). Reduction of fat content of ice cream makes a product of lost textural properties and mouth feel as compared to full fat ice cream (Aime et al., 2001). It 6 has been reported that dairy milk sales have decreased globally by 7% in 2015 due to the negative health perception of diary-based product consumption. Plant-based food diets however have become more inclusive within personalized nutrition plans for more than 70% of consumers (FMI, 2017). The avocado (Persea Americana), a tree likely originated from southcentral Mexico, is classified as a member of the flowering plant family Lauraceae (RBG et al., 2010) The fruits of the plant also called an avocado (or avocado pear or alligator pear), is botanically a large berry containing a single large seed. The avocado may be originated in southern Mexico but was cultivated from the Rio Grande to central Peru long before the arrival of the Europeans. Thereafter, it was carried not only to West Indies, but to nearly all parts of the tropical and subtropical world with suitable environmental conditions. Now avocado is grown commercially in most parts of the world. (Morton, 1987). Ghanaian avocados range in size, shape, color and flavor thanks to a large gene pool in the country. There are many local varieties and hybrids that offer unique fruit and fruiting qualities, from early bearing to late season, and from green-skinned to dark purple-black fruit at maturity (Baars et al., 2004). The peel may be thick and pebbled, as found in the Guatemalan race of avocados, thin and delicate, typical of the Mexican race, or smooth, leathery, and thin-to-medium in thickness, characteristics of the West Indian race (Christous et al., 2008). Hass is the most common type of avocado which is available in all parts of Ghana and even the world at large. Ghanaian avocados vary from pear-shaped to rounded, and can weigh as much as a pound or more (Peter et al., 2012). The pale green or yellow flesh can be more watery, fibrous, dry or buttery, depending on the variety and oil content. The flavor of avocado varies from mild to rich, and offers hints of sweetness or nuttiness. Ghanaian avocados are available year-round in the local markets 7 (Bhandari et al., 2005). Avocado is a highly caloric fruit with a good source of reliable and insoluble fibre, vitamin C, E, K, B complex, folate and phytochemicals such as phytosterol and carotenoids which possess antioxidant and radical scavenging activities (Lee et al., 2004). Avocados are good sources of potassium, carbohydrates and sugar (Slater et al., 1975). Furthermore, it is rich in monounsaturated fatty acids, especially oleic and palmitoleic acids, which is related to decrease risk of cardiovascular diseases because these fatty acids preserve levels of high –density lipoproteins and act as antioxidants (Richard et al., 2008). Thus, avocado can be considered as highly desirable additive to a healthy diet. According to the American Heart Association (Dietary Guidelines, 2008) reports that avocados can help consumers to meet the dietary guidelines which involves eating a diet of low fat content, rich in unsaturated fatty acids with lower cholesterol because avocados are the only fruits that contain monou saturated fats. Although avocado ice cream contains a lot of nutrients which is good for our health, the fruit avocado, used for making this snack is prone to bacterium specifically listeria which causes food borne illness (Catherine, 2019). The potential issue is that when you cut through the avocado’s pebbly skin, bacteria could be transferred to the knife. And then the knife could contaminate the avocado flesh. Before peeling off the produce before use, make sure that the skin is thoroughly washed and gently scrubbed under clean water to get rid of these bacteria and prevent crosscontamination from occurring. In addition, avocado easily undergoes enzymatic browning. This is because, avocado contains an enzyme called polyphenol oxidase, which causes the flesh brown when exposed to air or more specifically, when it is exposed to oxygen. So, in order to maintain that gorgeous green color, seal in an air tight container to maintain its color for some period of time before it is ready to be used (Racheal, 2019). Although the browning part of the avocado might look unappetizing and can taste bitter, it is still safe to consume (Nathaniel et al., 2020). 8 Consumers prefer plant-based diets (Ranganathan, 2016), which are more sustainable (Salonen, 2003) and able to provide better health benefits. The preference towards plant-based diets has significantly increased (Granato et al., 2010) with the rise of millennial generation who are increasingly adopting vegan and free-lactose diets (Flavera et al., 2008). It also has been reported that diary milk sales have decreased globally by 7% in 2015 due to the negative health perception of diary-based product consumption. It has been reported that people who consumed avocado regularly tend to have a sufficient nutrient supply of dietary fibre, vitamin K, vitamin E, potassium, magnesium as well as vitamin B complex (Fulgoni et al., 2010). The functions and importance of these nutrients in avocado to the human system are; DIETARY FIBRE The dietary fibre in avocado helps increase the weight and size of your stool and softens it. Hence, decreasing the chances of getting constipation. In case of releasing loose, watery stools, the fiber may help to solidify the stool because it absorbs water and adds bulk to stool which helps maintain bowel health (Fulgoni et al., 2010). Vitamin K helps to make various proteins that are needed for blood clotting and the building of strong bones (Fulgoni et al., 2010). VITAMIN E Vitamin E is a fat soluble nutrient, which acts as an antioxidant, capable of helping to protect the body cells from the damage caused by free radicals. Free radicals are compounds formed when our bodies convert the food we eat into energy (Fulgoni et al., 2010). 9 POTASSIUM Potassium helps your nerves to function and muscles to contract. It helps your heartbeat to stay regular and also helps to move nutrients into the cells and waste products out of the cell (Fulgoni et al., 2010). MAGNESIUM Magnesium helps to maintain normal nerve and muscle function, supports a healthy immune system, keeps the heartbeat steady and maintain strong bones. Magnesium also helps to adjust blood glucose levels and acids in the production of energy and protein (Fulgoni et al., 2010) VITAMIN B COMPLEX Vitamin B complex play a vital role in maintaining good health and well-being. As the building blocks of a healthy body, B vitamins have a direct impact on your energy levels, brain function and cell metabolism. Vitamin B complex helps prevent infections and helps support or promote cell health (Fulgoni et al., 2010) These nutrients provide a wide range of potential health benefits such as preventing hyperchostrolemia (Salonen et al., 2003), vascular damage (Jacobs et al., 2007), and reduce the risk of antherosclerosis (Dwyer et al., 2004). The consumption of avocado has been investigated to have positive effects on lipid profiles (Carranza et al., 1997) by increasing HDL cholesterol levels, reducing lipid serum peroxidation, and promoting cardiovascular health (Wu X et al.,2007). Furthermore, phytosterol has also been proven to be an effective compound against type-2-diabetis mellitus, lowering the risk of cardiovascular diseases, and preventing cancer (Jones et al., 2009). 10 Avocado has high fat content (USDA, 2011) which is a good source for substituting the milk fat in frozen diary desserts (Goff and Richard, 2013). Ice cream is one of the most widely consumed foods in frozen dairy desserts category (Goff and Richard, 2013). A series of different types of non-diary based ice cream have been developed due to rise of health concerns associated with milk consumption (Peter and Keigan, 2012), milk fat consumption that is dominated by SFA, and clean label issues (Barrs et al., 2004). A non-diary fat source derived from avocado could be a potential alternative in order to create an option for free-diary fat ice cream as well as provide better health benefits to the consumers. Plant-baseed fat sources in the ice cream formulation. Furthermore, plant-based replacement for diary-based fat sources is generally less expensive compared to diary fat (Goff and Richard, 2013) and provide advantages towards health (Salonen et al., 2003, Wu X et al., 2007). The objective of this study is to analyze the physiochemical, rheological and sensorial properties of ice cream that have been substituted with different concentrations of avocado paste. SKIMMED MILK POWDER Skimmed powdered milk, also called milk powder or historically dried milk, is a manufactured dairy product made by evaporating milk to dryness. Skim Milk Powder is obtained by removing water from pasteurized skim milk. It contains 5% or less moisture (by weight) and 1.5% or less milkfat (by weight) and a minimum milk protein content of 34% (Filomena et. al., 2010). One purpose of drying milk is to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Another purpose is to reduce its bulk for the economy of transportation. Powdered milk and dairy products include such items as dry whole milk, nonfat (skimmed) dry milk, dry buttermilk, dry whey products and dry dairy blends. Many exported dairy products conform to standards laid out in Codex Alimentarius. 11 USES AND BENEFITS DEEIVED FROM SKIMMED MILK POWDER CONSUMPTION Skimmed powdered milk is frequently used in the manufacture of infant formula, confectionery such as ice cream, chocolate and caramel candy, and in recipes for baked goods where adding liquid milk would render the product too thin. Powdered milk is also widely used in various sweets such as the famous Indian milk balls known as gulab jamun and a popular Indian sweet delicacy (sprinkled with desiccated coconut) known as chum chum (made with skim milk powder). Many no-cook recipes that use nut butters use powdered milk to prevent the nut butter from turning liquid by absorbing the oil (Tucker et al., 2013). Powdered milk is also a common item in UN food aid supplies, fallout shelters, warehouses, and wherever fresh milk is not a viable option. It is widely used in many developing countries because of reduced transport and storage costs (reduced bulk and weight, no refrigerated vehicles). Like other dry foods, it is considered nonperishable and is favored by survivalists, hikers, and others requiring nonperishable, easy-to-prepare food. Because of its resemblance to cocaine and other drugs, powdered milk is sometimes used in filmmaking as a non-toxic prop that may be insufflated (Wayne, 2009). NUTRITIONAL COMPOSITION AND SOME HEALTH IMPLICATIONS RELATED TO SKIMMED MILK POWDER Skimmed milk powders contain all 21 standard amino acids, the building blocks of proteins, and are high in soluble vitamins and minerals (MPNI, 2013). According to USAID, (USAID, 2006) the typical average amounts of major nutrients in the reconstituted nonfat dry milk are (by weight) 36% protein, 52% carbohydrates (predominantly lactose), calcium 1.3%, potassium 1.8%. Whole milk powder, on the other hand, contains an average of 25-27% protein, 36-38% carbohydrates, 12 26-40% fat, and 5-7% ash (minerals). In Canada, powdered skim milk must contain added vitamin D in an amount such that a reasonable daily intake of the milk will provide between 300 and 400 International Units (IU) of vitamin D (F.D.R, 2019). However, inappropriate storage conditions, such as high relative humidity and high ambient temperature, can significantly degrade the nutritive value of the skimmed milk powder (M. Okamato et al., 2020). Commercial skimmed milk powders are reported to contain oxysterols (oxidized cholesterol) (P.F Fox et al., 2006) in higher amounts than in fresh milk (up to 30 μg/g, versus trace amounts in fresh milk) (Dabrowski et al., 2016). Oxysterols are derivatives of cholesterol that are produced either by free radicals or by enzymes. Some free radicals-derived oxysterols have been suspected of being initiators of atherosclerotic plaques (PIFNS, 2019). For comparison, powdered eggs contain even more oxysterols, up to 200 μg/g (Dabdowski et al., 2006). SUGAR Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Table sugar, granulated sugar, or regular sugar, refers to sucrose, a disaccharide composed of glucose and fructose (FAO, 2019). Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double sugars, are molecules composed of two monosaccharides joined by a glycosidic bond. Common examples are sucrose (table sugar) (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose). In the body, compound sugars are hydrolysed into simple sugars (WHO, 2015). Longer chains of monosaccharides are not regarded as sugars, and are called oligosaccharides or polysaccharides. Starch is a glucose polymer found in plants, and is the most abundant source of 13 energy in human food. Some other chemical substances, such as glycerol and sugar alcohols, may have a sweet taste, but are not classified as sugar. Sucrose is used in prepared foods (e.g., cookies and cakes), is sometimes added to commercially available processed food and beverages, and may be used by people as a sweetener for foods (e.g., toast and cereal) and beverages (e.g., coffee and tea). The average person consumes about 24 kilograms (53 lb) of sugar each year, with North and South Americans consuming up to 50 kilograms (110 lb) and Africans consuming under 20 kilograms (44 lb) (FAO, 2020). As sugar consumption grew in the latter part of the 20th century, researchers began to examine whether a diet high in sugar, especially refined sugar, was damaging to human health. Excessive consumption of sugar has been implicated in the onset of obesity, diabetes, cardiovascular disease, dementia, and tooth decay. Numerous studies have tried to clarify those implications, but with varying results, mainly because of the difficulty of finding populations for use as controls that consume little or no sugar. In 2015, the World Health Organization recommended that adults and children reduce their intake of free sugars to less than 10%, and encouraged a reduction to below 5%, of their total energy intake (WHO, 2015). TYPES OF SUGAR Monosaccharides Fructose, galactose, and glucose are all simple sugars, monosaccharides, with the general formula C6H12O6. They have five hydroxyl groups (−OH) and a carbonyl group (C=O) and are cyclic when dissolved in water. They each exist as several isomers with dextro- and laevo-rotatory forms that cause polarized light to diverge to the right or the left (David et al., 2020). 14 Fructose Fructose, or fruit sugar, occurs naturally in fruits, some root vegetables, cane sugar and honey and is the sweetest of the sugars. It is one of the components of sucrose or table sugar. It is used as a high-fructose syrup, which is manufactured from hydrolyzed corn starch that has been processed to yield corn syrup, with enzymes then added to convert part of the glucose into fructose (Kretchmer et al., 2018). Galactose Galactose generally does not occur in the free state but is a constituent with glucose of the disaccharide lactose or milk sugar. It is less sweet than glucose. It is a component of the antigens found on the surface of red blood cells that determine blood groups (Raven et al., 2014). Glucose Glucose occurs naturally in fruits and plant juices and is the primary product of photosynthesis. Starch is converted into glucose during digestion, and glucose is the form of sugar that is transported around the bodies of animals in the bloodstream. Although in principle there are two enantiomers of glucose (mirror images one of the other), naturally occurring glucose is D-glucose. This is also called dextrose, or grape sugar because drying grape juice produces crystals of dextrose that can be sieved from the other components (George, 2013). Glucose syrup is a liquid form of glucose that is widely used in the manufacture of foodstuffs. It can be manufactured from starch by enzymatic hydrolysis (Schenck et al., 2017). For example, corn syrup, which is produced commercially by breaking down maize starch, is one common source of purified dextrose (CFR, 2020). However, dextrose is naturally present in many unprocessed, whole foods, including honey and fruits such as grapes (Ireland et al., 2010). 15 Disaccharides Lactose, maltose, and sucrose are all compound sugars, disaccharides, with the general formula C12H22O11. They are formed by the combination of two monosaccharide molecules with the exclusion of a molecule of water (CFR, 2020). Lactose Lactose is the naturally occurring sugar found in milk. A molecule of lactose is formed by the combination of a molecule of galactose with a molecule of glucose. It is broken down when consumed into its constituent parts by the enzyme lactase during digestion. Children have this enzyme but some adults no longer form it and they are unable to digest lactose (EBO, 2019) Maltose Maltose is formed during the germination of certain grains, the most notable being barley, which is converted into malt, the source of the sugar's name. A molecule of maltose is formed by the combination of two molecules of glucose. It is less sweet than glucose, fructose or sucrose (CFA, 2020). It is formed in the body during the digestion of starch by the enzyme amylase and is itself broken down during digestion by the enzyme maltase (EBO, 2019). Sucrose Sucrose is found in the stems of sugarcane and roots of sugar beet. It also occurs naturally alongside fructose and glucose in other plants, in particular fruits and some roots such as carrots. The different proportions of sugars found in these foods determines the range of sweetness experienced when eating them (Buzz et al., 2016). A molecule of sucrose is formed by the combination of a molecule of glucose with a molecule of fructose. After being eaten, sucrose is 16 split into its constituent parts during digestion by a number of enzymes known as sucrase (EBO, 2019). They have five hydroxyl groups (−OH) and a carbonyl group (C=O) and are cyclic when dissolved in water. They each exist as several isomers with Dextro and Levo rotatory forms that cause polarized light to diverge to the right or the left (David et al., 2019). HEALTH IMPLICATIONS RELATED FO EXCESSIVE INTAKE OF SUGAR Sugar refiners and manufacturers of sugary foods and drinks have sought to influence medical research and public health recommendations, (Mozaffarian, 2017) with substantial and largely clandestine spending documented from the 1960s to 2016 (Aaron et al., 2017) results of research on the health effects of sugary food and drink differ significantly, depending on whether the researcher has financial ties to the food and drink industry (Jessica et al., 2016). A 2013 medical review concluded "unhealthy commodity industries should have no role in the formation of national or international NCD [non-communicable disease] policy" (Rob et al., 2013). There have been similar efforts to steer coverage of sugar-related health information in popular media, including news media and social media (Eric, 2014). Obesity and Metabolic Syndrome A 2003 World Health Organization technical report provided evidence that high intake of sugary drinks (including fruit juice) increased the risk of obesity by adding to overall energy intake (WHO, 2003). By itself, sugar is not a factor causing obesity and metabolic syndrome, but rather, when over-consumed, is a component of unhealthy dietary behavior (Alexandra, 2013). Metaanalyses showed that excessive consumption of sugar-sweetened beverages increased the risk of developing type 2 diabetes and metabolic syndrome including weight gain (Hill et.al, 2019) and obesity in adults and children (Mallika et al., 2018). 17 Hyperactivity A 2019 meta-analysis found that sugar consumption does not improve mood, but can lower alertness and increase fatigue within an hour of consumption (Mantantzis et al., 2019). Some studies report evidence of causality between high consumption of refined sugar and hyperactivity (Davis et al., 2010). One review of low-quality studies of children consuming high amounts of energy drinks showed association with higher rates of unhealthy behaviors, including smoking and excessive alcohol use, and with hyperactivity and insomnia (Visram et al., 2016). Tooth decay The 2003 WHO report stated that "Sugars are undoubtedly the most important dietary factor in the development of dental caries" (WHO, 2003). A review of human studies showed that the incidence of caries is lower when sugar intake is less than 10% of total energy consumed (Anahad et al., 2015). VANILLA ESSENCE Vanilla essence is a solution made by macerating and percolating vanilla pods in a solution of ethanol and water. It is considered an essential ingredient in many Western desserts, especially baked goods like cakes, cookies, brownies, and cupcakes, as well as custards, ice creams, and puddings (Lior, 2016). Although its primary flavor compound is vanillin, pure vanilla extract contains several hundred additional flavor compounds, which are responsible for its complex, deep flavor (Rose, 2017). By contrast, artificial vanilla flavor is solely made up of artificially derived vanillin, which is frequently made from a by-product of the wood pulp industry (FSM, 2013). Because of the way that vanilla extract is made (that is, by macerating naturally brown vanilla 18 beans in alcohol), there is no possible way for it to be colorless or clear. Therefore, any clear vanilla flavoring is artificial (Baking bites, 2014). 19 CHAPTER THREE RESEARCH METHODOLOGY 3.0 MATERIALS Fresh full ripped avocado pear (Hass variety) was obtained from Koforidua Central Market. Fresh skimmed milk powder, cream, sugar and vanilla was purchased in a local market in Koforidua. All other solvents and chemicals needed for the analysis was obtained from the Department of Food and Postharvest Chemistry Laboratory. 3.1 STUDY LOCATION The study was conducted at the Food Product Development and the Chemistry Laboratory of the Department of Food and Postharvest Technology, Koforidua Technical University, Koforidua Ghana. 3.2 PREPARATION OF SAMPLES Table 3.1 Specifications of different ice cream mixes. Ingredients T1 T2 T3 T4 T5 T6 100 g 80g 70g 60g 50g 40g 0g 20g 30g 40g 50g 60g Distilled water 300ml 300ml 300ml 300ml 350ml 350ml Sugar 100g 100g 100g 100g 100g 100g 0.2g 0.2g 0.2g 0.2g 0.2g 0.2g (CONTROL) Skim milk powder Avocado Flavour (vanilla essence) 20 3.2.1 Preparation of Avocado Fruit Pulp The ripened avocado fruit was washed, dried, cut opened and flesh removed and mixed through using blender. The homogenate was packaged in plastic containers and cold stored at 4°C till used. The fruit pulp was freshly prepared directly before ice cream making. 3.2.2 Preparation of Ice cream; Ice cream mixes and ice cream was made as described by Charles and Williams (2019). Table one shows the formulation of different ice cream mixes. SAMPLE T1 Skim milk powder (100g) was first be mixed with 100g of sugar and 0.2g of flavor to form a mixture. 300ml distilled water was added to the mixture and stirred vigorously until a uniform solution was formed. The mixture was then heated at 80°C for 5 minutes. The pasteurized mixture was then be cooled to a temperature of 40°C. Sample T1 was then refrigerated at a temperature of 5°C between 12-24 hours. SAMPLE T2 Skim milk powder (80g) was first mixed with 100g of sugar and 0.2g of flavor to form a mixture. 300ml distilled water was added to the mixture and stirred vigorously until a uniform solution was formed. The mixture would then be heated at 80°C for 5 minutes. The pasteurized mixture was then cooled to a temperature of 40°C and 20g of the blended avocado fruit pulp was added and mixed thoroughly. Sample T2 was then refrigerated at a temperature of 5°C between 12-24 hours. 21 SAMPLE T3 Skim milk powder (70g) was first mixed with 100g of sugar and 0.2g of flavor to form a mixture. 300ml of distilled water was added to the mixture and stirred vigorously until a uniform solution was formed. The mixture was then be heated at 80°C for 5 minutes. The pasteurized mixture was then cooled to a temperature of 40°C and 30g of the blended avocado fruit pulp was added and mixed thoroughly. Sample T3 was then refrigerated at a temperature of 5°C between 12-24 hours. SAMPLE T4 Skim milk powder (60g) was first mixed with 100g of sugar and 0.2g of flavor to form a mixture. 300ml of distilled water was added to the mixture and stirred vigorously until a uniform solution was formed. The mixture was heated at 80°C for 5 minutes. The pasteurized mixture was then cooled to a temperature of 40°C and 40g of the blended avocado fruit pulp was added and mixed thoroughly. Sample T4 was refrigerated at a temperature of 5°C between 12-24 hours. SAMPLE T5 Skim milk powder (50g) was first mixed with 100g of sugar and 0.2g of flavor to form a mixture. 300ml of distilled water was added to the mixture and stirred vigorously until a uniform solution was formed. The mixture was heated at 80°C for 5 minutes. The pasteurized mixture was cooled to a temperature of 40°C and 50g of the blended avocado fruit pulp was added and mixed thoroughly. Sample T5 was refrigerated at a temperature of 5°C between 12-24 hours. SAMPLE T6 Skim milk powder (40g) was first mixed with 100g of sugar and 0.2g of flavor to form a mixture. 300ml of distilled water was added to the mixture and stirred vigorously until a uniform solution 22 was formed. The mixture was then heated at 80°C for 5 minutes. The pasteurized mixture was cooled to a temperature of 40°C and 60g of the blended avocado fruit pulp was added and mixed thoroughly. Sample T6 was then refrigerated at a temperature of 5°C between 12-24 hours. The avocado fruit pulp would be used in different proportions that is (T2: T3: T4:T5: T6, 20g, 30g, 40g, 50g and 60g respectively). The frozen mixtures would then be whipped in an ice cream mixer (Taylormate Model 152, Taylor Company, Blackhawk Blvd, USA). The ice cream would then be collected into 100 ml plastic cups, covered, hardened and stored at a temperature of -18°C for one day until analysis. 23 FLOW DIAGRAM OF AVOCADO ICE CREAM PREPARATION. Washing and cutting of avocado Scooping and blending of avocado Packaging and storing of avocado paste in a refrigerator at a temperature of 4°c Mixing all measured dried ingredients together for ice cream preparation Pasteurize the mixture at a temperature of 80°c for 5 minutes Cool the pasteurized mixture with cold water to reduce the temperature to 40°c Add the cooled avocado paste to the mixture and mix to achieve a homogeneous mixture. Refrigerate the mixture at a temperature of 5°c between 12-24 hours. Whip the mixture in an ice cream maker machine. Package the ice cream into plastic cups with thight fitting lid. Store packaged ice cream in the freezer at a temperature of -18°c. 24 PROXIMATE ANALYSIS ON AVOCADO Moisture Content Determination The moisture content of the samples was determined using the method as described by AOAC, (2005). The crucibles were washed and dried in an oven for 20 minutes. It was then cooled in a desiccator. 4g of the sample was weighed into previously weighed crucibles and was transferred into an oven set at a temperature of 103°C for 4 hours. At the end of the four hours, the samples were removed and were placed in a desiccator to cool then weighed. % Moisture: W2 - W1/W2 - W0 × 100 Where; WO: weight of empty crucible W1: weight of crucible sample. W2 weight of crucible dried sample Ash Content Determination Three grams of sample was weighed using an analytical balance (SARTORIUS B120S, GERMANY). The weight of the crucible and each sample was determined and recorded. The crucible and its content were placed in the muffle furnace (THERMO SCIENTIFIC) at 600 degree celcius for 2 hours cooled in desiccators and weighed. The procedure was repeated for each sample in triplicates (AOAC,2000). The percentage ash was determined using the following formulae. %Ash = W2 - W1 × 100/W3 25 Where; W1 = weight of empty crucible W2 = weight of ashes sample W3 = weight of sample Crude protein determination The crude protein of the ice cream was analyzed using Kjheldah method. 3 grams of the ice cream sample was weighed using an analytical balance (SARTORIUS B120S, GERMANY) and was placed in a digested flask. 25ml of concentrated H2SO4 and Kjheldah catalyst was added. Digestion was carried out in the digestion chamber until a clear solution is obtained. The digested sample was filtered into a 100ml volumetric flask and made to the mark with 60ml distilled water and mixed well. 70ml of NaOH and 10ml of the sample were put into the Kjheldah apparatus and be heated for the distillation of Ammonia. 25ml of 4% boric acid was measured into the conical flask to receive the liberated ammonia gas. The nitrogen content was estimated by titrating the ammonium borate formed with standard 0.096N HCL using mixed indicator and titer values recorded. The procedure was repeated for each sample in the (AOAC 2000). The protein content was calculated using the formula. Protein % = (A - B) × 14.007 × 6.25/W Where; A = volume (ml) of 0.2N HCL used sample titration B = volume (ml) of 0.2N HCL used in sample titration 26 14.007 = atomic weight of nitrogen 6.25 = the protein-nitrogen conversion factor. Determination of Total Soluble Solids. A hand held refractometer (Atagos master series, Japan) was used. The refractometer was standardized by placing a drop of distilled water on the prism. The refractometer was placed in such a way that it allowed entry of sunlight into the prism. The refractometer was placed such that it allowed entry of sunlight into the prism. The eye-piece was used to observe the standardization after adjusting the coarse and fine adjustment properly. The process was repeated in triplicate and the results were recorded. A hand held refractometer (Atagos master series, Japan) was used. The refractometer was standardized by placing a drop of distilled water on the prism. The refractometer was placed in such a way that it allowed entry of sunlight into the prism. The Determination Of pH The digital bench top Ph meter (Ph/ORP/ISE meters) equipped with an electrode wasused in the determination. The electrode was washed in distilled water. It was then placed in each sample. The Ph reading was read from the recorder of the Ph meter (AOAC, 1990). Fat content determination 2gram avocado fruit pulp sample which the moisture content had been determined was used. The beakers were weighed using an analytical balance (SARTORIUS B120S, GERMANY). The samples were transferred into a thimble and placed in a holding chamber of the Goldfish apparatus. An amount of petroleum ether was poured into each of the beakers. Asbstos was placed on top of 27 each sample in the thimble, the thimbles were then inserted in the gaskets of the condenser. The beaker containing the solvents was also connected to the gaskets. The tap was then opened to allow free flow of water through the apparatus to facilitate the condensing of the solvents. The apparatus was switched on and the sample extracted for 4 hours within a rate of 5 drops per second. The beakers and its content were dried in an oven (FISHER Isotemp oven SENIOR MODEL) for 30minutes, cooled in a desiccator for 30minutes and weighed on an analytical balance (SARTORIUS B120S GERMANY) to determine the difference in weight of the flask. This procedure was repeated for each sample in triplicates (AOAC,2000).The fat content was calculated using the formula %Crudefat=W1/W2 × 100 W1 = fat weight W2 = sample weight Crude fiber content determination The sample used for the fat determination will be used for the crude fiber analysis. The defatted sample was transferred into 500ml Erlenmeyer flask and 0.5g of the asbestos and 200ml of 1.25% boiling hydrogen sulphate was added and connected to a condenser and set on a hot plate. The flask boiled for 30minutes, its content was filtered out and washed with boiling water until the washings are no more acidic. The residues were put into a flask, connected to the condenser and made to boil with 200ml of 25% NaOH for 30minutes. It was then filtered and washed with bottling water till filtrate was no longer basic and 1.5ml alcohol was used to do the final washing. Residues will then be transferred into silica crucible and dried in an electric oven (FISHER Isotemp oven, SENIOR MODEL) for an hour at 100 degree Celsius. It is then cooled in a desiccator and weighed 28 and loss in weight would be determined. The procedure was repeated for each sample in triplicates (AOAC,1990).The crude fiber content was calculated using the formula %Crude fiber = (C1 - C2) × 100/C3 Where; C1 = weight of dried sample C2 = weight of ashed sample C3 = weight of defatted sample Carbohydrate Determination The carbohydrate content was determined by the method of difference AOAC (1990). The quantity of carbohydrate was calculated by the following equation. Carbohydrate =100 - (Ash + moisture + protein + fat + fiber). 3.3 PROXIMATE AND PHYSIOCHEMICAL ANALYSIS ON AVOCADO ICE CREAM. 3.3.1 Moisture Content Determination The moisture content of the sample was determined using the method as described by AOAC, (2005). The crucibles were washed and dried in an oven for 20 minutes. It was then cooled in a desiccator. 4g of the sample was weighed into previously weighed crucibles and was transferred into an oven set at a temperature of 103°C for 4 hours. At the end of the four hours, the samples were removed and were placed in a desiccator to cool then weighed. % Moisture: W2-W1/W2-W0×100 29 Where; WO: weight of empty crucible W1: weight of crucible+ sample. W2= weight of crucible + dried sample 3.3.2 Ash Content Determination The ash content was determined by the methods as described by AOAC (2005). 4g of each sample was weighed into a weighed crucible, which has been dried in an oven ad cooled in a desiccator. It was then transferred into an electric furnace set at 550°C for 8 hours. After the 8 hours, the crucibles with samples were then cooled in the desiccator before it was weighed. Weight of sample = (wt of sample + wt of crucible)−wt of crucible Weight of sample= ash − empty crucible % Ash =weight of ash/weight of sample×100 3.3.3 Crude Protein Determination The protein content was determined by the Kjeldahl Nitrogen method as described by AOAC (2005). In brief, 1 liter of the samples were weighed unto a filter paper. The filter paper was folded into a long protein tube (test tube). 25ml of concentrated H2SO4 was measured onto the sample in the test tube. One khejedal tablet was added to the mixture in the test tube. The tube was fixed onto a digester for 90 minutes at a temperature of 400°C to digest all the nitrogen to ammonium sulphate. After the digestion, the test tubes were fixed onto a digestion machine. 100ml of 40% NaOH and 150ml of water was added to the samples in distillatory. 30 The mixtures were steam distilled for 2 minutes into 500ml conical flask containing 10ml of 4% Boric acid with three drops of screened methyl red as indicator and placed at the receiving top of the condenser. The solution was then titrated against 0.1036N HCL in a 50ml burette. % Nitrogen=[H+] × titer × (molar mass) ×100÷ sample wt×100 %Nitrogen=[H+] × (titer - blank) ×molar mass ÷ sample wt×10 The %nitrogen was then multiplied by a correction factor to obtain the %crude protein. Correction factor= 6.25 % Crude protein= (%nitrogen) × (correction factor) 3.3.5 Crude Fat Determination The fat content was determined using AOAC (2005). In brief, 2g of each sample were weighed unto a filter paper, cotton was placed inside a thimble, the sample were placed on the cotton and covered with extra nonabsorbent cotton to create an environment for the extraction. 90ml of petroleum ether which boils at 40°C was measured. The petroleum ether was poured into the flask containing the thimble o completely cover the surface. The flask was then fixed onto the soxtherm apparatus for 3 hours. After the 3 hours the sample was removed from the beaker leaving the extract at the bottom of the beaker. The extract was then dried in an oven for 1 hour. After 1 hour, the beaker was removed from the oven and allowed to cool. The sample was then weighed. Fat content= weight of beaker-weight of dried sample. %Fat= fat content ÷ weight of sample×100 31 3.3.6 Free Fatty Acid Determination. The free fatty acid content of the ice creams was determined by a modification of the solvent extraction procedure. 30 grams of melted ice cream mix were weighed into 250ml centrifuge bottles. The ice cream was diluted with 10ml of distilled water and titrated with 1N H2SO4. The titrated mixture was shaken vigorously with 40ml of ethanol for 30 seconds and allowed to stand for 5 minutes. 60ml of ethyl ether was added and the mixture was swirled for some seconds. The mixture was then centrifuged for 10 minutes at 2,000 r.p.m. The fat layer of the solvent was then transferred to a fat dish by siphoning and the extracted fat was freed from solvent by allowing the pans to stand at room temperature overnight. The last traces of solvent were removed by placing the fat in a 60°C oven at 50mm mercury for 10 minutes. The free fatty acid content of the extracted fat was determined by the method of Breazeale and Bird. One gram of the day was dissolved in 5ml of absolute ethanol and 15ml of petroleum ether. Ten drops of phenolphthalein solution were added and the solution was titrated for the first definite color change with 0.01N KOH using a 5ml micro-burette. 3.3.7 Determination Of pH The digital bench top pH meter (pH/ORP/ISE meters) equipped with an electrode was used in the determination. The electrode was washed in distilled water. It was then placed in each sample. The pH reading was read from the recorder of the pH meter (AOAC, 1990). 3.4 Determination of Total Soluble Solids. The total soluble solid (TSS) were determined using a moisture analyzer (MB45 Ohaus). 32 3.5 Overrun The overrun was determined using an exact measurement of volume and weight of the ice cream mixture before and after mixing (Hammink, Practical Analysis, 2014). The formula used for calculating the overrun was; %Overrun= V2 - V1/V1×100 Where; V2= volume of ice cream V1= volume of ice cream mix 3.6 Melting Rate The melting rate was quantified using the dripping method by which an amount of ice cream (ml) was dripped over time (ml/min) at room temperature. A funnel was placed on top of a measuring cylinder (100 ml) and a filter paper was placed inside the funnel. The amount of liquid that was dripped into the measuring cylinder was recorded after 60 minutes. Total Antioxidants determination DPPH radical scavenging activity was determined as described by Okawa et al with slight modification. Solutions of known Trolux with concentration were used for calibration. Trolux was mixed with 250ml of methanolic DPPH. The homogenate was shaken vigorously and kept in darkness for 30minutes. Absorption of the sample was measured on the spectrophotometer at 515πm. Results were expressed as Trolux equivalent per gram of dry weight. 33 SENSORY EVALUATION Man accepts food on the basis of certain characteristics that he defines and perceives with his senses. These attributes are described in terms of sensations and are sometimes referred to as qualitative or sensory qualities. They include perceptions of appearance factors such as color, shape and flavor factors or sensations combining odor and taste Appearance: Appearance is the surface characteristics of the food judged by eye or feeling with hands. Appearance influence food appreciation and quality especially the consumer acceptance. It includes color, shape and size characteristics of food (Gellynck et al., 2008). Colour: colour affects our acceptance of food. Color of the food is one which is important to determine the quality of the food. At the time of observing the food the first impression on the acceptance of the food is formed. Surface color depends both on the physicochemical characteristics of the ice cream mixture and on the operating conditions applied during freezing. Maillard browning caused by the reaction between milk proteins and the added sugar (Akubor and Obiegbuna, 2002), is the crucial factor that affects the color of ice creams during pasteurization. The other factor that affects the color of the ice cream product as far as avocado fruit pulp is concerned is oxidation, which is influenced by the activation of enzyme with the aid of oxygen. Flavor: The interaction of taste, odor and textural feeling provides an overall sensation which is best defined by “flavor” Flavor and texture of avocado ice cream are key attributes to the consumer acceptance (Heinio, 2006). Volatile flavor compounds which found in milk powder are playing a key role in the perception of the ice cream flavor (Molnar, 2000). However, the perceived ice cream flavor often relies on the type of band method of production and shelf life (Lior, 2006). 34 Taste: is the gustatory perceptions caused by soluble substance which found in the mouth (Molnar, 2000). For the period of eating or consuming the food the taste receptors (taste buds) are stimulated and create the taste sensation. It can be described as salty, sweet, bitter and sour (Belitz et al., 2009). It depends on the chemical composition of the food. Foods containing sugar taste sweet while those foods which contain salt taste salty. Thus, the taste of foods is one factor which contributes to the acceptability of food. Tastes may increase the apparent intensity of odors may also increase the apparent intensity of taste (Gellynck et al., 2008). The ice cream samples were evaluated using 30 semi-trained sensory panelists who were selected from Koforidua Technical University. They were asked to evaluate the colour, flavour, taste, aroma, texture and overall acceptability of each sample. The panelists were properly briefed and instructed individually on the procedure with emphasis on rinsing their mouth with water in between sample tasting using a 5 point hedonic scale where 1 is like very much, 2 is like, 3 is neither like nor dislike, 4 is dislike and 5 is dislike very much. In order to avoid biased evaluation by panelists, the various ice cream samples were coded. Warm water was given to them to wash their mouth before tasting and in between tasting session. QUESTIONNAIRE The research instrument used in this study was the questionnaire. Questionnaire is a set of questions that have been specially formulated as a means of collecting information and surveying opinions on a specified subject or theme. The questionnaire was used to access the sensory qualities and overall acceptability of the avocado ice cream produced. The questionnaire contained both open and closed-related questions. In the open-ended questions, respondents were given the opportunity to express their thoughts about the properties of the avocado fruit pulp used in the 35 preparation of ice cream while with the closed-ended questions using a 5-ponit hedonic scale, possible answers were provided for respondents to select from. DATA ANALYSIS All experiments were conducted in triplicate. One-way Analysis of variance (ANOVA) was performed on each of the variables. The data obtained from the study was analyzed using statistical package for social science (SPSS) version 20. The significant differences was determined using Fisher’s Least Significant Difference (LSD) at p < 0.05. The results was expressed as means and standard deviations. 36 CHAPTER FOUR RESULTS AND DISCUSSION 4.0 INTRODUCTION This chapter presents the results and discussion from the lab. The data was analysed using SPSS Software to determine the mean and standard deviation of the sensory evaluation for the low fat ice cream prepared with different percentages of avocado fruit pulp. The statistical analysis was based on the objective of the study which includes; performing proximate analysis and also evaluating the consumer acceptability of the various formulations. 4.1 CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY OF THE AVOCADO FRUIT PULP. Table (4.1) constitutes the chemical composition and antioxidant activity of the avocado fruit pulp used in the production of the ice cream without any treatment. Table 4.1 Chemical composition and antioxidant activity of Avocado Constituents. Content Protein 1.34±0.13 Moisture 6.21±0.03 Ash 1.52±0.05 Fiber 5.14±0.08 Total Soluble Solids 6.21±0.13 pH 6.50±0.03 Fat 12.21±0.18 Antioxidant activity 39.51±0.44 Table (1) shows that the avocado fruit pulp can be considered as a non-acidic fruit, rich in fat content and moderate percentage of protein (1.34%), moisture (6.51%), ash (1.52%), fibre (5.14%) 37 and total soluble solids (6.21oBrix). The avocado fruit pulp had high antioxidant scavenging activity (39.15%). The composition of Avocado fruit pulp of used variety (Hass), fall in reported composition of avocado fruit (Maitera et.al 2014). Also, several bioactive compounds are beneficial to human health such as liposoluble vitamin E, K and β-carotene (USDA, 2011). In addition, avocado fruit pulp is characterized by a rich mouthfeel, acceptable flavour, and taste. The composition and sensory properties of avocado fruit pulp suggest that it can be added as functional ingredient in low fat dairy products to impart the fat rich taste to these products. 4.1.1 SENSORY EVALUATION TASTE Table (4.2) shows the results obtained after the panelists analysed the attribute of the various samples in relation to the attribute taste. Table 4.2 Results of samples in relation to the attribute taste Sample. Mean. Standard Deviation T1 1.87 0.97b T2 1.57 0.68a T3 1.77 0.73b T4 2.27 0.94c T5 2.20 1.03bc T6 2.53 1.20ab Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=;The least value in the samples for each attribute represents the highest accepted attribute for each sample. 38 The mean sensory score for taste of the ice cream samples of different formulation are shown in Table 2. Statistical analysis showed that the partial substitution of avocado paste in the ice cream samples had significant effect (p<0.05) on the taste of the different ice cream formulation. Sample B recorded the highest score of 1.57±0.68 for taste whiles sample F had the lowest value of 2.53±1.20. The taste of the sample with 20% avocado paste (sample B) replacement recorded the highest rating for taste with a mean value of 1.57 which was not significantly different from sample with 30% avocado paste (sample C) which recorded mean of 1.77. The sample with 30% avocado paste replacement was ranked second as far as taste is concerned with a mean value of 1.77; followed by 0% avocado paste (sample A which is the control) with a mean of 1.87 and the least was sample with 60% of the avocado paste (sample F) with a mean value of 2.53. The taste ranking did not increase proportional as the level of avocado paste increased. From the results, there is a strong indication that, the ice cream sample with 20% replacement of avocado paste gave panelists the highest and the most preferred taste followed by a 30% (sampl C) and 50% (sample E) avocado paste replacement if there is a taste preference decision to be taken on only the avocado ice cream product. There was no significant difference between the control 0% avocado paste, 20% (sample B) and 30% (sample C) avocado paste replacement but a significant (p<0.05) different as the level of avocado paste increased above 30% replacement. 39 COLOUR Table (4.3) shows the results obtained after the panelists analysed the attribute of the various samples in relation to the attribute colour. Table 4.3 Results of samples in relation to the attribute colour Sample. Mean. Standard deviation T1 1.80 0.76b T2 1.73 0.64a T3 1.83 0.75b T4 2.40 0.89a T5 2.30 0.92ab T6 2.37 0.96a Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; The least value in the samples for each attribute represents the highest accepted attribute for each sample. Colour is an important parameter to the quality of food products because of its association with factors such as freshness, ripeness, desirability, and food safety. It is often a primary consideration for consumers when making purchasing decisions. All ice cream samples containing avocado fruit pulp exhibited slight green colour of variable intensity according to the avocado fruit pulp ratio used. The panelists described the colour of the 5 ice cream samples (sample T2, T3, T4, T5, and T6) as new. From the results the colour for the various samples ranges from a mean of 1.80 to 2.37. The sample with 20% (sample T2) avocado paste replacement and 0% (sample T1 which is the control) avocado paste replacement recorded the maximum mean for colour of 1.73 and 1.80 respectively, followed by sample C produce from a 30% substitution of the avocado fruit pulp 40 attained a mean of 1.83. The respond found no significant different in colour between sample with 0%, 20% and 30% (sample T1, T2 and T3 respectively) avocado fruit pulp replacement as well as sample with 40%, 50% and 60% (sample T4, T5 and T6 respectively) avocado fruit pulp incorporation. The results showed a colour preference order of sample T2 (1.73±0.64), sample T1 (1.80±0.76), Sample T3 (1.83±0.75), Sample T5 (2.30±0.92), Sample T6 (2.37±0.96) and Sample T4 (2.40±0.89). FLAVOUR Table (4.4) shows the results obtained after the panelists analysed the attribute of the various samples in relation to the attribute flavour. Table 4.4 Results of samples in relation to the attribute flavour Sample. Mean. Standard Deviation T1 1.87 0.86a T2 1.80 0.55b T3 2.07 0.94c T4 2.40 0.93c T5 2.30 0.92c T6 2.60 1.13c Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=;The least value in the samples for each attribute represents the highest accepted attribute for each sample. Flavour is an important parameter of food, good” flavour from food excites the taste buds, making the system ready to accept the product. “Poor” flavour may cause outright rejection of food before they are tasted. A good level of flavour intensity influences taste (Pearson et.al, 2019). From the 41 results of the sensory evaluation of the six products under study, the statistical analysis showed that the partial substitution of avocado fruit pulp with skimmed milk powder had significant effect (p< 0.05) on the flavor of the different ice cream formulation. Sample T2 (20% avocado fruit pulp incorporation) obtain the highest score, giving it a better preference for flavour which was significantly different from sample T1 (0% avocado fruit pulp incorporation), this shows that, incorporation of whole milk with avocado fruit pulp has effect on flavor characteristics of ice cream (Carrari et.al, 2006) product with 30%, 50%, 40% and 60% avocado fruit pulp replacement was rated second most preferred with respect to flavour with mean of 2.07, 2.30, 2.40 and 2.60 respectively which was not significantly different (p< 0.05) from each other. From the result it can be concluded that as the amount of avocado fruit pulp incorporated into the mixture increases, the acceptability on flavor of product goes on decreasing. AROMA Table (4.5) shows the results obtained after the panelists analysed the attribute of the various samples in relation to the attribute aroma. Table 4.5 Results of samples in relation to the attribute aroma Sample. Mean. Standard deviation T1 1.80 0.76a T2 1.77 0.57b T3 2.03 0.76a T4 2.47 0.94ab T5 2.43 0.86b T6 2.57 1.17ab Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different 42 superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=;The least value in the samples for each attribute represents the highest accepted attribute for each sample. Statistical analysis showed that the partial substitution of the vanilla essence and avocado paste in the ice cream samples had significant effect (p<0.05) on the aroma of the different ice cream formulation. Sample T2 recorded the highest score of 1.77±0.57 for taste whiles sample T6 had the lowest value of 2.73±1.34. The aroma of the sample with 20% avocado paste replacement recorded the highest rating for aroma with a mean value of 1.77 which was not significantly different from sample with 0% avocado paste (sample T1) which recorded mean of 1.80. The sample with 0% avocado paste replacement was ranked second as far as aroma is concerned with a mean value of 1.80; followed by 30% avocado paste (sample T3) with a mean of 2.03 and the least was sample T6 which contained 60% of the avocado paste with a mean value of 2.73. The aroma ranking did not increase proportional as the level of avocado paste increased. From the results, there is a strong indication that, the ice cream sample with 20% replacement of avocado paste gave panelists the highest and the most preferred aroma followed by a 30% of avocado fruit pulp (sample T3) and 40% (sample T4) avocado paste replacement if there is anaroma preference decision to be taken on only the avocado ice cream product. There was no significant difference between the control 0% avocado paste and 20% (sample T2) of the avocado paste replacement but a significant (p<0.05) different as the level of avocado paste increased above 20% replacement. 43 MOUTHFEEL Table (4.6) shows the results obtained after the panelists analysed the attribute of the various samples in relation to the attribute mouthfeel. Table 4.6 Results of samples in relation to the attribute mouthfeel Sample. Mean. Standard deviation T1 1.83 0.79a T2 1.87 0.86b T3 2.03 0.76bc T4 2.47 0.97c T5 2.50 1.11c T6 2.73 1.34ab Each value is presented as mean ± standard deviation. Means within a row with the sample letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=;The least value in the samples for each attribute represents the highest accepted attribute for each sample. The product with the 40%, 50% and 60% avocado fruit pulp replacement was rated the least as far as mouth-feel is concern with mean rating of 2.47 (sample T4), 2.50 (sample T5) and 2.73 (sample T6) respectively which was not significantly (p< 0.05) different from each other. While the sample produce from only 100% skimmed milk powder (sample T1) was the highest. The sample with 20% avocado fruit pulp replacement was rated at 1.87 which was the second highest, whiles the 30% replacement was rated with a mean value of 2.03. The control product obtained the highest mouthfeel. Similarly, to a study by (Emma et al., 2019). Which suggests that when the proportion of incorporated avocado fruit pulp increased in the ice cream, the mouth feel of ice cream scores 44 decreased significantly, the mouth feel of the ice cream products understudy decreases significantly with 20%, 30%, 40%, 50% and 60% avocado fruit pulp replacements. OVERALL ACCEPTABILITY Table (4.7) shows the results obtained after the panelists analysed the attribute of the various samples in relation to the overall acceptability. Table 4.7 Results of samples in relation to the overall acceptability Sample. Mean. Standard deviation T1. 1.67 0.80a T2. 1.67 0.55b T3. 1.90 0.84c T4. 2.47 0.94ab T5. 2.30 0.92c T6. 2.83 1.39abc Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=;The least value in the samples for each attribute represents the highest accepted attribute for each sample. The descriptive statistics of the overall satisfaction of panelists have with the entire product. The overall acceptability of the samples ranged from 1.67±0.80 to 2.83±1.39. Maximum score value of overall acceptability from five-point hedonic scale was (1.67±0.80) recorded by Sample T1 100% skimmed milk powder with 0% avocado fruit pulp and (1.67±0.35) recorded by Sample T2 which contained 80% of the skimmed milk powder and 20% of the avocado fruit pulp, while the minimum score value (2.83±1.39) was scored by sample T6 which contained 40% of the skimmed milk powder and 60% of the avocado fruit pulp. It was noted that, there was no significant 45 difference between sample T1 and sample T2 but there was a significant difference in the overall acceptability of sample T3, sample T4, sample T5 and sample T6 products. The overall acceptability of samples was significantly different (p<0.05). It was observed that the increase in avocado fruit pulp substitution decreased the overall acceptability of the ice cream. The decrease in overall acceptability may be due to the results of appearance, texture, aroma and taste of the ice cream with different amounts of skimmed milk powder and avocado fruit pulp or could be because the panellist was not familiar with the control product. The results on acceptability agreed with those reported in previous related studies where it was found out that substitution levels of avocado fruit pulp in ice cream decrease the overall acceptability (Pearson et al., 2019). 4.2. PHYSIOCHEMICAL PROPERTIES OF THE VARIOUS ICE CREAM SAMPLES Table (4.8) shows the physiochemical properties (pH and TSS) of the various ice cream samples. Table 4.8 Physiochemical properties (pH and TSS) of the various ice cream samples. Sample. pH. TSS T1. 6.65±0.14a. 0.32±0.004a T2. 6.56 ±0.00b. 0.33±0.006b T3. 6.49±0.01b. 0.31±0.016c T4. 6.52±0.01c 0.33±0.017e T5. 6.32±0.04ab 0.32±0.014d T6. 6.50±0.00b. 0.34±0.013b Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=; D=; E=; 46 4.2.1 pH In chemistry, pH, (historically denoting "potential of hydrogen" or "power of hydrogen") (Jensen et al., 2004) is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions (solutions with higher concentrations of hydrogen ions) are measured to have lower pH values than basic or alkaline solutions. The pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution. This is because of the formula used to calculate pH approximates the negative of the base 10 logarithm of the molar concentration of hydrogen ions in the solution. More precisely, pH is the negative of the base 10 logarithm of the activity of the hydrogen ion (Bates et al., 2019). At 25°C, solutions with a pH less than 7 are acidic, and solutions with pH greater than 7 are basic. Solutions with a pH of 7 at this temperature are neutral (example, pure water). The neutral value of the pH depends on the temperature being lower than 7 if the temperature increases. The pH value can be less than 0 for a very strong acid or greater than 14 for very strong bases (Lim et al., 2006). When the pH of a solution is more than 5.9 but less than 7, it is considered as a weak acid. The pH of aqueous solutions can be measured with a glass of electrode and a pH meter, or a colour-changing indicator. Measurement of pH are important in chemistry, agronomy, medicine, food production, water treatment and many other applications. Table (8) shows the results obtained after analysing the pH of the various samples. pH showed no significant difference between the formulations. However, the trend showed that, the addition of avocado paste lowered the acidity level of the ice cream. The acidity level of avocado was between pH 6.2-6.6 depending on the type of cultivar, ripening stage, and maturity of the fruit. The range of pH from each formulation of sample T1, sample T2, sample T3, sample T4, sample T5 and sample T6 demonstrated that they were on the standard acidity level of the ice cream mixtures 47 (Goff et al., 2013). The acidity of ice cream is important because it determines the whipping capability that contributes to the stability of the ice cream (Goff et al., 2013). 4.3 Total Soluble Solids Total Soluble Solids measures the sugar solutions which the sugar is the main component using a refractometer. Total Soluble Solids content of a solution is determined by the index of refraction. This is measured using a refractometer and it is referred to as the degrees Brix. Brix is the term used when a refractometer equipped with a scale, based on the relationship between refractive indices at 20°C and the percentage by mass of total soluble solids of a pure aqueous sucrose solution. This tests the solids concentration of a sucrose contained solution. Sugar concentration is expressed in degrees Brix. At 20°C, the Brix is usually considered equivalent to the percentage of sucrose (sugar) in the solution (Emma et al., 2015). Table (8) shows the results that was derived after analysing the total soluble solids of the six samples. The total solid measurement demonstrated that there was no significance difference between sample T1 which is the control, sample T2 (which had 20% of the avocado fruit pulp), sample T3 (which had 30% of the avocado fruit pulp), sample T4 (which had 40% of the avocado fruit pulp), sample T5 (which had 50% of the avocado fruit pulp), and sample T6 (which had 60% of the avocado fruit pulp). And it was noticed that the temperature of the ice cream was suitable hence, producing accurate results and met the standard required for the ice cream to be consumed on the market (Carrari et al., 2006). The suitability of the ice cream was due to the storage treatment given to it. The soluble solids to titrable acidity ratio was constant throughout the sample test due to the controlled temperature storage. During the storage, the constant trend of TSS/TA was conducive in MAP than other treatment although the effects of treatments were insignificant. 48 4.4 NUTRITIONAL COMPOSITION OF THE VARIOUS ICE CREAM SAMPLES Table (9) shows the nutritional composition (moisture, total fat%, FFA, Antioxidant activity and protein%) Table 4.9 Nutritional composition (moisture, total fat%, FFA, Antioxidant activity and protein%) SAMPLES MOISTURE TOTAL FFA ANTIOXIDANT PROTEIN% % FAT % T1 65.86±0.14a 12.28±0.06a 2.34±0.06b 0.54±0.08a 3.70±0.07a T2 65.79±0.01a 11.54±0.04b 2.48±0.06a 33.8±0.52b 3.68±0.06b T3 65.40±0.06b 10.64±0.01c 3.25±0.07b 67.6±0.70c 3.32±0.02abc T4 64.37±0.03c 9.76±0.04d 3.27±0.38c 101.4±1.1d 3.61±0.06c T5 64.37±0.03d 8.68±0.06e 3.64±0.06d 135.2±1.5 e 3.51±0.06e T6 63.76±0.04 e 8.01±0.07 f 3.83±0.02 e 169±1.89 f 3.50±0.07 f ACTIVITY Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=;D=; E=; F=. 4.4.1 MOISTURE CONTENT Moisture content of food is the quantity of water contained in a given sample of food. Even though, water may be present in every moist substance, moisture content may include other mass losses such as alcohol and other organic solvents. The moisture content of foods is important to food manufacturers for a variety of reasons. Moisture is an important factor in food quality, preservation and resistance to deterioration. Water is a major constituent of most food products. The 49 approximate, expected moisture content of a good can affect the choice and method of measurement. Determination of the moisture content of food is necessary to calculate the content of other food constituent on a uniform basis. Moisture content of the food material is important to consider the food is suitable before the consumption, because moisture content affects the physical, chemical and biological aspects of food which relates with the freshness and stability. Moisture content of foods can be determined by a variety of methods, but obtaining accurate and precise data is commonly a challenge (Emmanuel et al., 2019). Moisture loss from a sample during analysis is due to the time and temperature factors. From the above analysis done, the results that was obtained in table (8) for the percentages of moisture content for the various samples were; sample T1 obtained 65.86% of moisture, sample T2 obtained 65.79% of moisture, sample T3 obtained 65.49% of moisture, sample T4 obtained 64.37% of moisture, followed by sample T5 which had 64.37% of moisture and lastly, sample T6 obtained a 63.76% of moisture respectively. Based on the results obtained, the weight changed in drying method are assumed to be due to moisture loss. Ice cream should contain 55-65% water (Kwang et al., 2014). Ice cream mixture with high water content will result in a low total solid content in general and proportionately higher water that is available to freeze when hardened at the same temperature compared to the ice cream mixture with low water content and high total solids. This condition affected the quality of the ice cream particularly for the texture and hardness. A knowledge about moisture content is often necessary to predict the background and behavior of foods during processing example mixing, drying, freezing, flow through a pipe or packaging. Foods are heterogeneous materials that contain different proportions of chemically bound, physically bound, capillary, trapped or bulk water. Moisture assay can be one of the most important analysis performed on food and yet one of the most difficult experiment to get an accurate and 50 precise data. It is therefore important for food scientist to be able to reliably measure moisture from foods to prolong the shelf life of foods (Pearson et.al., 2019). 4.5 TOTAL FAT DETERMINATION There was a significance difference (p<0.05) in total fat content for each formulation. The data showed that the highest fat content was obtained by sample T1 (12.28%), followed by sample T2 (11.54%), sample T3 (10.64%), sample T4 (9.76%), sample T5 (8.68%) and sample T6 (8.01%). Skimmed milk powder act as one of the base ingredients in the ice cream production and contributed up to 35.1% (w/w) of total fat content while avocado fruit contributed around 12.21% (w/w) of total fat including MUFA and the phytosterol (USDA, 2011). The differences in fat content of each formulation are due to the reducing fat source from the skimmed milk powder that has subsequently substituted with avocado paste. This fat content contributes to the fat crystallization and was able to influence the textural properties of the ice cream (Pelan et al., 1997). Ice cream contains at least 10% of dairy fat, 20% of total milk solid and able to establish a certain percentage of overrun, which is increasing vin volume by whipping air into the ice cream mixture (Goff et al., 2013), (Brian, 2014), (Karaman et al., 2012). The percentage of fat, total solids and overrun are important factors in ice cream quality (Goff et al., 2013). It has been demonstrated that the increase in dairy fat and total solid lead to higher costs in ice cream products, since dairy fat is considered as an expensive ingredient. However, this ingredient is the main structure in constructing sensorial properties and determines quality of the ice cream (Hui Y et al., 2004). The role of fat, particularly milk fat in ice cream is important to act as an air stabilizer during the freezing process which creates a dispersed phase of air bubbles (Goff et al., 2013). During the freezing process the crystalized fat and partially coalesced fat globule stabilize the air bubbles of the ice cream mixture and provide the desired foamy texture which contributes to the hardness 51 quality of the ice cream (Goff et al., 2013). Milk fat acts as a thermal insulator which affects the melting properties of the ice cream (Newton et al., 2014), (Li Z et al., 1997). Ice cream with high milk fat can retain its shape and take longer time to melt. In this experiment, the substitution of milk fat with avocado paste proportionally at 0%, 20%, 30%, 40%, 50% and 60% resulted in reducing the amount of total fat content and retained the melting rate. This substitution of dairy fat into plant-based fat from avocado was able to lower the total fat content of the ice cream mixture. This might be due to the fibre content in avocado paste that has the ability to lower the water mobility in the ice cream (Dello et al., 2004), (Gelrath et al., 2001). 4.5.1 FREE FATTY ACID DETERMINATION Free fatty acids are long chain acids that are not conjugated or attached to anything else and they are free and not bonded to any atom (Emma et al., 2019). Much attention has been given to the action of normal milk lipase in milk, and investigations have been conducted with the view of establishing the fatty acid threshold level (Dunkley et al., 1938). Also, the concentration of free acids in butter and cheese has been related to flavour characteristics of these products (Gould et al., 2018). Lipase action in relationship to ice cream quality has not been given specific attention. Such consideration seems justified for three reasons. First, rancid and closely related flavours are found in ice cream. This indicates that under certain conditions of processing and manufacturing, or through improper control of dairy products used, a sufficient quantity of free fatty acid is developed to produce the 'off' flavour. This matter becomes increasingly important as greater use is made of low-heat condensed or concentrated milk products as a source of the milk solids. In certain of these products, sufficient active lipase may remain to create a flavour problem unless proper precautions are used in processing. Second, free fatty acids when added to the mix have been found to be related to shrinkage in ice cream (Dahle et al., 2001). However, no studies have 52 been made of the relationship of shrinkage to the free fatty acid content of ice cream resulting from normal lipase action. Third, a certain concentration of free fatty acid has been found to be beneficial in improving the flavour of milk (Hollender et al., 2018). The possibility exists that controlled lipolysis may be utilized by the ice cream maker in the production of avocado ice cream with higher consumer acceptance. On the basis of the data presented, it appears that the FFA content of the various sample’s merits attention. The fatty acid-rancid flavor threshold in ice cream is more than twice the threshold value of 2.0 established for milk or cream (Dunkley et al.,1938). This indicates that the other components in the ice cream obscure the rancidity and made difficult its detection by organoleptic means. The obscuring effect of sample T6 which contained 60% of the avocado paste was appreciably greater than that for the other samples most especially sample T1. The acid degree of the strictly fresh ice cream which is the control (sample T1) appears to be definitely higher than the other samples. Non-dairy products may contribute to the acid-degree of ice cream under certain conditions. The fact that the free fatty acid of the various samples was just below the threshold level of rancidity poses an interesting question as to whether or not the small concentration of free acids may be beneficial to the flavour of the various samples. 53 4.6 ANTIOXIDANT ACTIVITY Figure 4.1 Antioxidant capacity standard calibration curve. Antioxidants are chemical substances that can neutralize and scanvage the free radicals, which are continuously produced by the body (Yazdanparast et al., 2007). Antioxidant activity or capacity of dairy products is mainly due to sulfur containing amino acids such as, cysteine, phosphate, Vitamin A, E, carotenoids, zinc, selenium, enzyme systems, superoxide dismutase, catalase, glutathione peroxide, milk oligosaccharides and peptides that are produced during fermentation. Antioxidant activity of dairy products can be enhanced by phytochemicals supplementation while fermented dairy products have been reported to contain higher antioxidant capacity as compared to the non-fermented dairy products. Literature review has shown that most dairy products have 54 antioxidant capacity, however, information regarding the antioxidant capacity of milk and its products have not been previously compiled. Fig (4.1), shows the results for the antioxidant capacity curve which was obtained after the analysis on the various samples were tested. Both the table and the figure show change of the antioxidant activity of the various ice cream samples during frozen storage as affected by using different percentages of the avocado fruit pulp. The control which is sample T1, had lower antioxidant activity than those of low fat ice cream which is sample T2, T3, T4, T5 and T6. This may be attributed to the differences in the mixtures which correlated to its content of protein and nonprotein antioxidants. The protein group includes various kinds of enzymes, and also a number of proteins and peptides which had phenolic compounds and antioxidant activity power (Lindmark et al., 2000). Addition of avocado fruit pulp in the 5 samples (T2, T3, T4, T5 and T6) increased significantly (p<0.01) the antioxidant activity of the low fat ice cream with respect to the percentages of the avocado fruit pulp added. This may be due to the addition antioxidant activity of the fruit pulp (Table 1) and also a possible oxidation process for the nutrients of the various samples. Similar findings reported by (El-Samahy et al., 2015) for low fat ice cream made with added cactus pear fruit pulp as a natural antioxidant obtained an increase in the antioxidant activity of the sample during it stored period. 4.6.1 PROTEIN DETERMINATION Ice cream is a very complex food. The water dissolves the sugars (lactose). There is colloidal system suspended in the water. The milk proteins constitute the colloids in one suspension, and the insoluble salts constitute another. Anther system that depends on water is the emulsion phase, and all systems coexist (Kilara et al., 2002). Therefore, the adsorption of protein is influenced by the type of fat and the emulsifier used in the ice cream manufacture. According to USDA, the 55 amount of protein contained in an ice cream ranges from 3.5%-4.0%. But there would not be any negative effect when the protein content in an ice cream increases beyond this range since there might be other factors involved which may lead to the increment in the protein content. Table (8) shows the results obtained after the 6 samples were analyzed for protein. There was no significant different between the various samples (T1, T2, T3, T4, T5 and T6) (p< 0.05) under study. The results obtained after the analysis tally with the protein range (3.5-4.0%) in any ice cream sample. Sample T1 had the highest protein content of 3.70%, followed by sample T2, sample T4, sample T5 and sample T6. Sample T3 had the least value for protein and this may be due to some factors like the freezing temperature and the ingredients used. 4.7 PHYSIOCHEMICAL PROPERTIES (OVERRUN AND MELTING RATE) OF THE VARIOUS ICE CREAM SAMPLE. Table (4.10) shows the physiochemical properties (overrun) of the various ice cream samples. Table 4.10 Overrun percentage. SAMPLE OVERRUN T1 55.48±0.06a T2 46.77±0.06b. T3 52.30±0.06c T4 56.18±0.06d T5 60.42±0.06e T6 70.00±0.06 f Each value is presented as mean ± standard deviation. Means within a row with the same letter superscript is not significantly different (P>0.05 Tukey’s test) whereas those with different superscripts are significantly different = (P<0.05 Tukey’s test). A=; B=; C=;D=; E=; F=. 56 The overrun showed significant difference (p<0.05) among the formulations. The data showed that increasing the avocado paste substitution towards milk fat in the ice cream mixture significantly reduce the overrun of the ice cream. The highest overrun achieved by sample T1 (55.48%), sample T2 (46.77%), sample T3 (52.30%), sample T4 (56.18%), sample T5 (60.42%) and sample T6 (70.00%). Based on Duncan test, it showed significant difference between sample T1 and sample T2 (p<0.05) but no significant difference between sample T4, sample T5 and sample T6 and the other formulations. The data for the overrun is in line with the melting rate where sample T1 had the highest overrun ability followed by rapid melting rate properties. The higher overrun significantly contributed to the higher melting rate in the ice cream (Rosalina et al., 2004), (Brain R, 2014). High overrun level in ice cream resulted to high melting rate due to instability of air cells Incorporated in the ice cream mixture (Brain R, 2014). The instability is due to the increase in temperature levels when ice cream is unfrozen. Moreover, the overrun also affected the hardness profile of ice cream (Rosalina et al., 2004). Overrun and air cell distribution becomes critical parameters in the ice cream industry that continuously needs to be controlled and monitored. There are numerous factors that could influence the development of air cells and affect overrun in ice cream products such as mixing, freezing, hardening, the use of stabilizers, homogenization, and ingredients used in the ice cream mixture (Goff et al., 2013), (Rosalina et al., 2004). Air content in the ice cream mixture contributed to the physical properties of the ice cream such as texture, hardness, melting properties and other sensorial characteristics (Rosalina et al., 2004). The amount of air incorporated in the colloidal system in the ice cream mixture influenced the distribution of the air size that could provide melting profile and directly affect the sensory quality parameters of the ice cream (Rosalina et al., 2004). 57 The presence of air cells in the ice cream mixture is important in determining the texture quality of the ice cream. It has been suggested that the amount of air cells at 70% overrun is enough to prevent collision among ice crystals and the lower the overrun will subsequently create larger ice crystals, thus lead to the increase of hardness of the ice cream (Prindiville et al., 1999). Air is one of the important ingredients that need to be incorporated in the ice cream mixture. It makes up between 30%-50% of the total volume of the ice cream (Brian, 2014). It has been reported that the stability of air cells could slow down the melting rate of the ice cream as determined by adding saturated monoglycerides to the ice cream mixture (Pelan et al., 1997). 4.8 MELTING RATE Figure 4.2 Results of melting rate. The melting rate of any substance depends on the temperature and fiber content of that substance. The melting rate showed significant difference between formulations (p<0.05). It is demonstrated from figure 2 that sample T2 had the highest melting rate, followed by sample T3, sample T1, sample T4, sample T5 and sample T6 respectively. The higher concentration of avocado paste in relation to degree of temperature resulted in the decrease in melting rate of sample T6. The 58 temperature and fiber content in the avocado paste could have affected the melting rate of the samples been observed. It has been reported that frozen dairy dessert formulated with dietary fibre could improve the melting quality of an ice cream (Stieven, 2009) depending on the type of fibre used (Stieven, 2009). Fibre with high soluble fraction capability such as insulin affects the rheology of the ice cream and could provide potential cryoprotective action (Stieven, 2009). The result showed that the fibre in insoluble compounds decrease significantly the melting rate of the samples but due to temperature differences, the control (sample T1), had a decrease in its melting rate as compared to sample T2 and T3 (Christous et al., 2009). Fibre has water binding properties that creates a lower melting rate of ice cream mixtures due to a reduction in water molecule mobility from bulk aqueous phase into the ice crystal surface phase (Christous et al., 2009), (Stieven, 2009). The addition of fibre from fruits such as avocado in ice cream mixtures decreases the melting rate of the ice cream (Christous et al., 2009). Fibre can contribute to the modification and improvement of food texture and sensory characteristics due to its water-binding capacity, gel forming ability, texturizing, and thickening effects (Dello et al., 2004), (Gelroth et al., 2001). Dietary fibre could promote an effective control of ice crystalization and ice crystal growth during freezing and storage as well as improve the melting and viscosity properties for the ice cream products (Christous et al., 2009), (Dello et al., 2004), (Gelroth et al., 2001). 59 CHAPTER FIVE 5.0 CONCLUSION Avocado fruit (Persea Americana) can be used as a functional ingredient in ice cream due to its flavour, natural antioxidant, fiber content in addition to its essential monounsaturated fatty acids constituents and related health promoting characteristics. This fruit pulp had unique characteristics which makes it suitable to be applied in low fat ice cream making. Avocado fruit pulp improved the rheological characteristics, the antioxidant activity, melting characteristics and total acceptability of ice cream. Therefore, this fruit pulp can be used successfully in making functional low fat ice cream of acceptable sensory attributes comparable with that of full fat ice cream. From the results obtained after analysing the melting rate of the various ice cream samples, it was observed that sample T6 had the most suitable melting rate as compared to the other samples this is because it contained a higher percentage of the avocado fruit pulp. The most suitable amount of Total soluble solids, pH, Total fat, Free fatty acids antioxidant activity, protein and overrun were observed in sample T2 (0.33±0.006b), sample T1 (6.65±0.14a.), sample T6 (8.01±0.07f), sample T6 (8.01±0.06f), sample T6, (169±1.89f), sample T2 (3.68±0.06b) and sample T2 (46.77±0.06b) respectively. Taking into consideration the overall accepted sample based on the various attributes involved during analysis as far as sensory evaluation is , it can be concluded that, sample T2 was highly accepted over all the other samples hence, making sample T2 ( which contained 20% of the avocado paste) highly recommended. 60 5.1 RECOMMENDATION 1. 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