PENGOLAHAN SUSU Bagian 1 EMMA RIFTYAN, S.TP., M.SC FPB21119 Teknologi Pengolahan Hasil Pertanian The composition of milk is generally described in terms of its commercially important constituents, milk fat and non-fat solids or milk solids not fat (MSNF). The MSNF consists of protein, lactose, and minerals. These solids are also referred to as “serum solids.” The term “total solids” refers to the serum solids plus the milk fat. Milk Enzymes Phospholipid Milk Fat Globules Water is the medium in which all the other components of milk (total solids) are dissolved or suspended WATER (87,7%) Whey/Serum Protein Cholesterol (3,25% fat) FAT (3,4 - 5,1%) PROTEIN Vitamins Minerals Casein Milk fat occurs in milk as an emulsion of fat particles suspended in aqueous phase. The spherical particles are called fat globules Milk fat functions as a concentrated source of energy as well as a source of fat-soluble vitamins A, D, E, and K and essential fatty acids, linoleic acids, and arachidonic acids. The essential fatty acids are not synthesized by the human body. They must be supplied by the diet. The major proteins of milk are broadly classified as caseins and whey proteins. Caseins are defined as the proteins that are insolubilized and precipitate at or above 20% when the pH of milk is lowered to 4.6. The soluble fraction at pH 4.6 is termed as whey proteins. Casein, the principal milk protein, makes up 80% of the total, while whey proteins make up the remaining 20%. The interaction of various caseins and calcium phosphate contributes to the formation of large colloidal complex particles called casein micelles. The whitish colour of milk is ascribed to the light scattering effect of colloidal micelles. Whey proteins consist of BETAlactoglobulin and ALPHA-lactalbumin, bovine serum albumin, immunoglobulins (mainly IgG1, IgG2, and IgM), lactoferrin, proteose peptone, and a number of diverse enzymes. All the whey proteins are superior in biological value as compared to caseins and compare with the quality of egg albumins. The major carbohydrate of milk, LACTOSE monohydrate, ranges from 4.8% to 5.2%. Lactose content constant. of milk is relatively In colostrum and mastitic milk, concentration is significantly lower. its It constitutes 52% of MSNF, non-fat dry milk, and 34% whey protein concentrate, and 70% of whey solids. It is a disaccharide of one residue each of d-glucose and dgalactose. In sweetening power, lactose is only 16–33% as sweet as sucrose. This makes lactose uniquely suitable for certain food applications. Toppings, icing, and various types of fillings are examples of use where its inclusion in the formulations can improve the quality. Lactose contributes significantly to the flavour, texture, appearance, shelf life, and toasting qualities of baked foods. The role of lactose in yogurt and fermented milks is extremely important because the culture nutritionally requires it as a substrate for growth. It is a source of carbon and after fermentation about 30% of the lactose content is converted to lactic acid. A compound formed from lactose in heated milk products is LACTULOSE. It stimulates the growth of Bifidobacterium bifidum and is thus beneficial in establishing useful microflora in the gut. Milk contains both fat-soluble (A, D, E, and K) and several water-soluble vitamins. In the production of low-fat and skim milk, the fat-soluble vitamins get concentrated in the cream fraction. Whole milk is a good source of vitamin A but the separation process leads to low vitamin A content in low-fat and skim milk. Average normal milk is considered to contain 0.70% ash and this amount represents a salt content of about 0.90% The percentage of salt and ash in milk varies with the breed, feed, season, and stage of lactation and disease. The calcium content of milk influences the firmness of curd during cheese making and the viscosity of fermented milks. From a nutritional standpoint, milk is an excellent source of calcium and phosphorus. Their ratio in milk is optimal for bone formation and bone health. SNI 01- 3141-1998 Susu merupakan sumber protein hewani yang dibutuhkan dalam pertumbuhan dan perkembangan tubuh serta dalam menjaga kesehatan. Susu sapi segar merupakan unsur penting dalam industri pengolahan susu. Sebagai pangan asal hewan, susu bersifat mudah rusak (perishable food). Dalam rangka meningkatkan peran susu segar dalam negeri dan perlindungan terhadap konsumen dan produsen, telah ditetapkan standar nasional SNI 01- 31411998 mengenai standar susu segar Class I is milk used for beverage products. This includes “white” whole, lowfat, and skim milk in all container sizes, chocolate and other flavoured milks, liquid buttermilk, and eggnog. Class II is milk used for soft manufactured products like yogurt and cultured dairy products, sour cream, ice cream, and other frozen dairy desserts, cottage cheese, and creams. Class III is milk used to manufacture cream cheese and hard cheeses. Class IV is milk used to make butter and dry milk products—principally nonfat dry milk. Food Milk Product Raw Milk Quality Specifications Standard plate count (SPC) Coliform bacteria count Laboratory pasteurized count (LPC) measure of the total bacteria count, and measures the overall microbiological quality of milk. measure of milk sanitation measure of heat-stable bacteria that may survive pasteurization. High SPC can cause reduced shelf life of the finished product High coliform counts reflect poor milking practices and unsatisfactory cleanliness of the dairy operation. performed by heat-treating laboratory samples to simulate batch pasteurization at 62.8°C (145°F) for 30 minutes and enumerating the bacteria that survive using the SPC method High SPC can cause off flavours from enzyme activity and elevated acidity. Coliform count is an indicator that food poisoning organisms may be present. Bacillus cereus is a common soil microorganism that can survive pasteurization, resulting in a high LPC. Raw Milk Quality Specifications Preliminary incubation (PI) count Somatic cell count (SCC) Titratable acidity (TA) measure of bacteria that will grow in refrigerated conditions. measure of milk sanitation measure of the lactic acid content of milk. PI type of bacteria are destroyed by pasteurization but can still result in lower quality milk due to enzymatic activity on the protein High coliform counts reflect poor milking practices and unsatisfactory cleanliness of the dairy operation. High bacteria counts produce elevated lactic acid levels as the bacteria ferment lactose. Coliform count is an indicator that food poisoning organisms may be present. The normal range of TA in fresh milk is 0.13% to 0.16%. High PIs (3- to 4-fold higher than SPCs) are generally associated with inade- quate cleaning and sanitizing of either the milking system or cows and/or poor milk cooling Raw Milk Quality Specifications Temperature Flavour the temperature of milk must never exceed 7°C (45°F). The milk should be fresh and clean with a creamy appearance. A recommended standard is 5°C (40°F) or less Elevated bacteria counts can produce offflavours (for example, acid, bitter). A recommended standard is that no offflavour exists. Appearance A recommended standard is “White, clean, no debris, and filter screen of 2 or less (sediment test).” Raw Milk Quality Specifications Antibiotics and other drugs may not be present in milk. To be considered organic, no milk can be used from a cow that has been treated with antibiotics without a 12-month holding period following treatment. For conventional milk, a treated cow will be withheld from the milking herd for about 5 days. Added water Testing the freezing point of milk using a cyroscope indicates if abnormal amounts of water exist in the load. In most states it is illegal to have a freezing point above −0.530° Hortvet scale. A recommended standard should be −0.530° Hortvet or less. Sediment measured by drawing 1 pint of sample through a cotton disk and assigning a grade of 1 (good) to 4 (bad) to the filter. Fat and milk-solids-not-fat (MSNF) FDA standards of identity for milk of 3.25% fat and 8.25% MSNF. The journey of milk from farm to market. refrigerated or insulated. They hold milk up to 72 hours (usually 24 hours) before processing. Grade A milk for pasteurization must be stored at 1.7°C to 4.4°C (35°F to 40°F). The maximum bacterial count at this stage is 300,000 CFU/ml, Fluid Milk Products Fluid Milk Products The shelf life of milk is a function of the microbial quality of raw milk, temperature, and time of exposure during storage and handling, pasteurization conditions, equipment sanitation, packaging conditions, and subsequent distribution practices. Fluid milk products display maximum keeping quality when stored at temperatures close to the freezing point (4°C/39.2°F). Let us assume the shelf life of pasteurized milk is 40 days at the storage temperature of 0°C (32°F). It has been demonstrated that the shelf life is shortened to 20 days by storage at 2°C (35.6°F), 10 days at 4°C (39.2°F), 5 days at 7°C (44.6°F), and progressively to fewer days at higher temperatures. Cream is prepared from milk by centrifugal separation. Heavy cream contains not less than 36% fat and may be called heavy whip- ping cream. Light whipping cream contains 30% or more milk fat, but less than 36% milk fat and may be labeled as whipping cream. Light cream, coffee cream, or table cream contains not less than 18% milk fat, but less than 30% milk fat. Plastic cream contains 80% milk fat. It resembles butter in consistency but compared to butter, it is still oil-in-water type emulsion. As an ingredient, it can be stored in frozen form. Fluid Cream The heated milk is concentrated in energyefficient multi-effect evaporators that operate in high vacuum condition to boil off water at moderate temperatures of 46.1°C to 54.4°C (115°F to 130°F). contains 60% sugar in the water phase, which imparts a preservative effect. concentrated milk that is homogenized and heat sterilized in sealed cans or bottles. Condensed milk may be low fat and non-fat. It is derived from milk after the removal of 60% of its water. It must contain at least 8% milk fat and 28% milk solids. made by boiling off 60% of the water content of milk. It must contain at least 6.5% milk fat and 23% milk solids. Evaporated milk is heatsterilized. Evaporated milk source of milk solids in dairy applications and in the manufacture of ice cream, frozen yogurt, and other frozen desserts. Condensed milks are generally customized orders. Sweetened condensed milk obtained by removing water from milk and contains at least 7.5% milk fat and 25.5% milk solids. Condensed milk is avail- able in whole milk, low-fat, and non-fat varieties. Condensed whole milk is purchased largely by confectionary industries. It is pasteurized but not sterilized by heat. It may be homogenized and supplemented with vitamin D. Condensed skim milk Concentrated milk or condensed whole milk Concentrated/Condensed Fluid Milk Products Cultured/Fermented Dairy Products Yogurt is a semisolid fermented product made from a heat-treated and standardized milk mix by the activity of a symbiotic blend of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Prebiotic and probiotic cultures currently are also used in the manufacture of fermented milks and yogurt products to enhance the functional or wellness attributes. A detailed discussion on types of yogurt and their manufacture is available in Chandan and O’Rell (2006a and b). Plain yogurt is a raw material for frozen yogurt, certain margarine products, and salad dressings.
