EGG SCIENCE AND TECHNOLOGY EMMA RIFTYAN, S.TP., M.SC STRUCTURE OF THE EGG Yolk Albumen Shell Membranes Shell Egg size is usually characteristic of the species, approximatively related to the size of the parents (5 to 15%) and increases with hen age The shape of the egg is usually oval and can be characterized by its shape index: where D represents the diameter (minor axis) measured at the equator and L is the length (major axis). This index varies mostly between 0.7 and 0.75, the extreme values are ranging from 0.65 to 0.85. The surface (S) of an egg can be estimated taking into account its dimensions: where k1 is between 4.63 and 5.07 using the weight (W) of the egg The volume (V) of an egg can be calculated taking into account its diameter and its length: where k3 = 0.85 to 0.99 using the weight (W) of the egg k2 = 4.67, 4.68 or 4.69 for eggs with a weight respectively below 60 g, between 60 and 70 g or greater than 70 g. The egg white (or albumen) is a heterogeneous medium consisting of three parts (in addition to chalazae) that can be differentiated by their viscosity. The inner liquid layer (17% of the total weight of albumen) in contact with the yolk is surrounded by the thick white (57%). Structure and formation of the eggshell. (a) Transverse section of the eggshell: schematic view (left) and scanning electron photomicrographs of the shell and shell membranes (right) and of the upper area of the shell (center). (Photograph McKee, University of Montreal). (b) (b) Surface of forming egg during eggshell formation observed by scanning electron microscopy: interlacing fibers of eggshell membranes (left), presence of mammillary cores on eggshell membranes (center) and initiation of shell formation by the fusion of calcium carbonate crystals (right). COMPOSITION OF THE EGG The egg is composed of about 59% white and 31% yolk, contained in a shell corresponding to 10% of the total egg weight. Concerning the edible portion, the whole hen egg contains 74.4% water and two sets of major nutrients: proteins (12.3%) and an equivalent quantity of lipids (11.6%). All the vitamins (except vitamin C) are present, as well as many minerals and trace elements. The egg is also a source of easily digested fats, choline- and cephalinrich phospholipids, unsaturated fatty acids and cholesterol. COMPOSITION OF THE EGG YOLK The egg yolk represents about 30% of the full egg weight and contains more than 50% dry matter. A mass of 100g of product supplies 16g of proteins and more than twice of this amount regarding the lipids Protein Lipids Carbohydrates •Globular proteins, such as livetins, phosvitin and also some minor proteins are present in the egg yolk. •Livetins are made up of serum albumin (alivetin) 14%, glycoproteins (blivetin) 41% and immunoglobulins (glivetin) 45% of total livetins in egg yolk •vitamin-binding proteins(retinol,vitam inD,biotin,riboflavin) •Egg lipids are exclusively linked to egg yolk proteins to form lipoproteins •composed of triglycerides (65%), phospholipids (31%) and cholesterol (4%) •Considered as a negative aspect of the nutritional quality of the egg, •The egg yolk contains 0.7 to 1% of carbohydrates including 0.3% of free glucose •Other carbohydrates are bound to proteins (glycoproteins) or lipids (glycolipids such as cerebroside) Minerals and vitamins •Egg yolk has high levels of phosphorus •60% of phosphorus is included in phospholipids •egg compartment also contains most of the iron •Egg yolk contains all the fat-soluble vitamins in the egg. It also has high levels of water-soluble vitamins by comparison to egg white, except for niacin and riboflavin. Carotenoids •The color of egg yolk is due to carotenoids accumulated in the egg •The hen does not have the ability to synthesize carotenoids. Therefore all carotenoids exported into the egg come from the carotenoids found in the hen’s food. COMPOSITION OF THE EGG WHITE Egg white is composed of water, proteins and some minerals and vitamins. It also contains free glucose (0.4–0.9%) at a concentration two times higher than that found in blood plasma. Water is the major constituent of egg white; Minerals and vitamins Carbohydrates Protein •Proteins represent about 90% of the dry matter of egg white which is composed mainly of globular glycoproteins. •These proteins are particularly remarkable due to their antimicrobial properties covering a broad spectrum of activities •Egg white contains 0.8% carbohydrates. •Half of these carbohydrates are in the free form, mainly glucose at 98%. The other half is composed of monosaccharides, N-acetylated amino sugars, uronic acids and sialic acids. •The egg white contains all minerals essential for the development of the embryo, such as phosphorus, potassium and some trace elements (iodine, selenium), However, egg contents are low in sodium and calcium. •Egg white contains low levels of vitamins. Moreover, it contains no liposoluble vitamins, but only hydrosoluble vitamins belonging to the B group. EGG FUNCTIONALITY https://www.aeb.org/food-manufacturers/egg-functionality EGG FUNCTIONALITY EGG FUNCTIONALITY EGG FUNCTIONALITY EGG FUNCTIONALITY EGG PROCESSING EGG PROCESSING SYSTEMS • • IN-LINE PROCESSING EGG PROCESSING OCCURS AT THE SAME LOCATION AS THE EGG PRODUCTION FACILITY. THIS PROCESSING METHOD IS THE MOST EFFICIENT EGG COLLECTION AND PROCESSING OF EGGS AVAILABLE. EGGS ARE DELIVERED FROM THE EGG PRODUCTION FACILITY TO THE EGG PROCESSING FACILITY BY AN ENCLOSED AND REFRIGERATED CONVEYOR SYSTEM. EGG HANDLING AND PROCESSING IS PERFORMED WITH AUTOMATED EQUIPMENT. • OFF-LINE PROCESSING • EGG PROCESSING OCCURS SEPARATE FROM THE EGG PRODUCTION FACILITY. THIS PROCESSING METHOD UTILIZES SATELLITE FARMS. SATELLITE FARMS ARE EGG PRODUCTION FACILITIES THAT ARE LOCATED AT A DIFFERENT LOCATION FROM THE EGG PROCESSING FACILITY. EGGS PRODUCED AT SATELLITE FARMS MUST BE GATHERED AND DELIVERED TO THE EGG PROCESSING FACILITY. EGG HANDLING AND GATHERING IS PERFORMED WITH AUTOMATED EQUIPMENT. Egg Processing Conveyor Egg Production Egg gathering In-line egg processing Off-line egg processing PROCESSING FUNCTIONS 1) CLEANING THE EGGS • ALL EGGS IN THE UNITED STATES ARE WASHED IN WARM WATER WITH A MILD DETERGENT IN ORDER TO REMOVE ANY CONTAMINANTS (MANURE, GREASE, BLOOD, YOLK, ETC.) BEFORE THEY ARE SOLD FOR HUMAN CONSUMPTION. • EGGS ARE DRIED TO REMOVE AN EXCESS MOISTURE PRIOR TO PACKAGING. • REMOVAL OF CONTAMINANTS PREVENTS EGG SPOILAGE BY BACTERIA. • EGGS THAT ARE NOT CLEANED OR CONTAIN DEFECTS ARE REMOVED FROM THE PROCESSING LINE AND ARE NOT PACKAGED FOR HUMAN CONSUMPTION. PROCESSING FUNCTIONS 2) GRADING • GRADING REFERS TO THE PROCESS OF GROUPING EGGS ACCORDING TO SIMILAR CHARACTERISTICS, SUCH AS QUALITY AND WEIGHT. • EGG GRADING IS PERFORMED BY TRAINED PROFESSIONALS FROM THE UNITED STATES DEPARTMENT OF AGRICULTURE (U.S.D.A.). • THE USDA HAS A STRINGENT SET OF REQUIREMENTS FOR THE GRADING OF FRESH SHELL EGGS. • EGG GRADING IS DEPENDENT UPON EXAMINATION OF INTERNAL QUALITY FACTORS (E.G., CONDITION OF THE EGG WHITE AND YOLK, AIR CELL SIZE). PROCESSING FUNCTIONS GRADING CONTINUED • INTERNAL QUALITY FACTORS CAN ALSO BE DETERMINED BY CANDLING. • CANDLING INVOLVES • EGG GRADING IS ALSO DEPENDENT UPON EXTERNAL QUALITY FACTORS (E.G., SHAPE, TEXTURE, CLEANLINESS, AND SOUNDNESS OF THE SHELL). • AN EGG WITH A AA GRADE CONTAINS THE MOST DESIRABLE CHARACTERISTICS WHILE AN EGG WITH A B GRADE CONTAINS THE LEAST DESIRABLE CHARACTERISTICS. • EXTERNAL QUALITY HOLDING THE EGG TO A CONCENTRATED LIGHT SOURCE FOR VISUAL INSPECTION OF INTERNAL DEFECTS, SUCH AS BLOOD SPOTS OR DOUBLE YOLKS. CAN BE DETERMINED BY CANDLING FOR ILLUMINATION AND DETECTION OF EGG SHELL CRACKS. U.S.D.A. GRADING DIAGRAM Candling Ideal egg shape. Abnormal egg shape. U.S.D.A. GRADING FACTORS PROCESSING FUNCTIONS 3) SIZE DETERMINATION • SIZES ARE DETERMINED BY WEIGHT. THERE ARE SIX DIFFERENT WEIGHT CATEGORIES: PEEWEE, SMALL, MEDIUM, LARGE, EXTRA LARGE, AND JUMBO. EACH SIZE CATEGORY RECEIVES A DIFFERENT PRICE ON THE FARM AS WELL AS AT THE RETAIL LEVEL. • MINIMUM AVERAGE WEIGHT FOR ONE DOZEN EGGS • PEEWEE: 15 OUNCES • SMALL: 18 OUNCES • MEDIUM: 21 OUNCES • LARGE: 24 OUNCES • EXTRA LARGE: 27 OUNCES • JUMBO: 30 OUNCES PROCESSING FUNCTIONS 4) PACKAGING • EGGS ARE PACKAGED INTO A VARIETY OF CONTAINERS DESIGNED FOR SAFE SHIPMENT AND ENHANCED PRODUCT APPEARANCE FOR THE CONSUMER. • LOOSE PACKAGING IS A SIMPLE WAY OF MOVING LARGE QUANTITIES OF EGGS IN AN EFFICIENT BUT ALSO SIMPLE FASHION. LOOSE PACKAGING USUALLY REFERS TO EITHER A THIRTY EGG LARGE OR EXTRA LARGE FLAT, OR A TWENTY EGG JUMBO FLAT. LOOSE SALES MOSTLY CONSIST OF SALES TO RESTAURANTS OR OTHER LARGE QUANTITY CONSUMERS. • IN RETAIL SETTINGS, EGGS ARE OFTEN PACKAGED IN CARTONS CONTAINING EITHER ONE DOZEN OR EIGHTEEN EGGS. • THIS PACKAGING METHOD IS DESIGNED TO BE HANDLED BY THE FINAL CONSUMER AND IS THEREFORE USUALLY DESIGNED TO BE QUITE APPEALING. • THERE ARE SEVERAL DIFFERENT VARIETIES OF EGGS AVAILABLE TO THE CONSUMER, CALLED DESIGNER EGGS BY THE INDUSTRY. CARE AND HANDLING 1) REFRIGERATION • EGGS MUST BE COOLED TO A CORE TEMPERATURE OF 45 ˚F. • EGGS HELD PRIOR TO PROCESSING MUST ALSO BE COOLED. • ALL EGGS BEING TRANSPORTED MUST BE HAULED IN A REFRIGERATED TRAILER SO THAT THE CORE TEMPERATURE IS HELD CONSTANT AT 45 ˚F. CARE AND HANDLING 2) MECHANICAL HANDLING • EGGS ARE MOVED USING CONVEYOR SYSTEMS BETWEEN THE PRODUCTION FACILITY AND THE PROCESSING PLANT. • THE PROCESSING MACHINERY IS FULLY MECHANICAL AND MOST OF THE EQUIPMENT ON COMMERCIAL FARMS WORKS TO WASH, DRY, SORT BY WEIGHT AND QUALITY, AND PACKAGE THE EGGS INTO SPECIFIED PACKAGING. • ONCE EGGS ARE CONSOLIDATED TO PALLETS, FORK LIFTS ARE USED TO HANDLE THE PRODUCT. LABELING 1) SELL BY DATE EVERY INDIVIDUAL PACKAGE OF EGGS PROCESSED MUST DATE OF PROCESSING. CONTAIN A SELL BY DATE THAT IS SET FROM THE 2) JULIAN DATE THIS IS THE THREE DIGIT DAY NUMBER RELATIVE TO THE DAY IN THE YEAR THE EGGS WERE PROCESSED. THIS DATE IS CALCULATED WITH JANUARY 1 AS 001 AND DECEMBER 31 AS 365. THIS DATE IS LISTED NEXT TO THE PLANT CODE. 3) GRADE BOTH THE SIZE OF THE EGGS AND THE LEVEL OF QUALITY ARE PRINTED ON THE CARTON. MOST FRESH SHELL EGGS ARE SIGNIFIED BY AN A OR AA GRADE. 4) PLANT CODE A CODE IS PRINTED ON EVERY CARTON PRODUCED IN A PROCESSING PLANT. EACH PLANT HAS ITS OWN INDIVIDUAL CODE SO THAT IF THERE IS A NEED TO FIND THE ORIGIN OF THE FINISH PRODUCT, IT CAN BE TRACED ALL THE WAY BACK TO THE PROCESSING PLANT. CARTON LABELING LABELING 6) NUTRITIONAL FACTS NUTRITIONAL INFORMATION IS PRINTED ON EVERY PACKAGE FOR RETAIL SALE. THIS INFORMATION VARIES SLIGHTLY DEPENDING ON THE EGG SIZE AND ALSO THE TYPE OF EGG (DESIGNER EGGS). 7) “KEEP REFRIGERATED” ALL EGG PACKAGES ARE LABELED WITH A CAUTIONARY “KEEP REFRIGERATED” LABEL. REFRIGERATION HELPS REDUCE THE GROWTH OF SALMONELLA OR OTHER BACTERIA. 8) U.E.P. “ANIMAL CARE CERTIFIED” NATIONWIDE MANY EGG FARMERS HAVE VOLUNTARILY JOINED THE UNITED EGG PRODUCERS (U.E.P.), WHICH DEVELOPS REGULATIONS TO ENSURE THE OVERALL WELFARE OF CHICKENS BEING USED FOR EGG PRODUCTION. WHEN A FARM BECOMES “ANIMAL CARE CERTIFIED”, THIS LABEL INFORMS THE CONSUMER THAT THE PRODUCT WAS PRODUCED IN ACCORDANCE WITH ACCEPTED ANIMAL WELFARE STANDARDS. EGG PRESERVATION EGG DRYING Drying methods of egg: spray drying freeze drying Foam Mat Drying POWDERED EGGS POWDERED EGGS ARE FULLY DEHYDRATED EGGS. THEY ARE MADE USING SPRAY DRYING MAINLY. EGGS ARE A VERY NUTRITIOUS SOURCE OF FOOD THAT IS ONE OF THE CORNERSTONES IN BAKING. IT’S LOW-COST BUT HIGH-QUALITY SOURCE OF PROTEIN. POWDERED EGGS CAN BE USED WITHOUT REHYDRATION WHEN BAKING, AND CAN BE REHYDRATED TO MAKE DISHES SUCH AS SCRAMBLED EGGS AND OMELETTES. PROCESS FLOW CHART BREAKING OF EGGS AND REMOVAL OF SHELLS FILTRATION STORAGE AND DRYING PACKING 1. SPRAY DRYING PROCESS • The Manufacture of dried egg powder starts with breaking of eggs and removing egg-shells. • After removal of shells, the mixture is filtered and stored in storage tanks at about 4º C. • Then it is taken to tubular heater where in it is dried at about 65º C for 8 to 10 minutes and it is filtered • Then passed to high pressure spray drier with the help of high pressure pump. • The spray drying process enables the removal nearly all the water from eggs. of • THE BASIC FEATURE OF SPRAY DRYING THAT ENABLES THIS IS THE ATOMIZATION OF THE LIQUID EGG PRODUCT INTO A SPRAY OF DROPLETS THAT ARE DISPERSED INTO HOT AIR. • THE SPRAY HAS AN EXTENSIVE SURFACE AREA AND MOISTURE EVAPORATION IS VIRTUALLY INSTANTANEOUS. BECAUSE OF THAT, THE PRODUCT TEMPERATURE IS MAINTAINED WELL BELOW LEVELS THAT CAUSE POTENTIAL HEAT DAMAGE AND DETERIORATION IN THE VALUABLE PROPERTIES OF EGG PRODUCTS. • THE MATERIAL WHICH COMES OUT OF HIGH PRESSURE SPRAY DRIER IS DRIED AND POWDER FORM OF EGG. • WHICH IS THEN PACKED IN POLY-LINED BOXES. • THE AVERAGE YIELD IS AROUND 80%. 2. FOAM MAT DRYER This starts by whipping the raw material under controlled conditions using various means such a blender or specially designed devices in the presence of edible foam agent and/or foam stabilizer. The stable form foamed product is consequently spread as a thin sheet or mat to be exposed to stream of relatively hot air until it is dried to desired moisture. The drying process can systematically be performed under soft conditions with relatively low airflow temperature. It results in a thin porous honeycomb sheet or mat. The dried sheet product is then converted into fine powder by simple and easy grinding resulting in free-flowing powder FOAM PREPARATION EGG WHITE WAS KEPT UNDER REFRIGERATION (50C) A GRADUATED GLASS BEAKER WAS USED AS A CONTAINER TO MAKE THE EGG WHITE FOAM. 100 ML OF EGG WHITE WAS ADDED TO THE GLASS BEAKER. XANTHAN GUM (XG; MP BIOMEDICALS, INC., ILLKIRCH, FRANCE) AT 0.125% CONCENTRATION WAS USED AS A STABILIZER. A 250-W KITCHEN BLENDER WITH VARIOUS SPEED ADJUSTMENTS WAS USED FOR MAKING FOAM. THE XG OF 0.125% CONCENTRATION STABILITY OF EGG WHITE FOAM. THE TOTAL WHIPPING TIME WAS 5 MIN WAS ADDED GRADUALLY DURING THE WHIPPING FOR THE MAJOR ADVANTAGES OF POWDERED EGGS OVER FRESH EGGS THE PRICE. REDUCED WEIGHT PER VOLUME EQUIVALENT. THE SHELF LIFE. SMALLER USAGE OF STORAGE SPACE. LACK OF NEED FOR REFRIGERATION. OF WHOLE EGG 3. EGG ALBUMEN FLAKES EGG ALBUMEN FLAKES DRYING THE EGG WHITE MAKES EGG ALBUMEN FLAKES. THIS DRIED PRODUCT HAS A CRYSTALLINE APPEARANCE WITH GOLDEN YELLOW COLOUR. TECHNICAL GRADE FLAKES ARE USED IN TANNING OF LEATHER, IN OFFSET PRINTING AND AS ADHESIVE IN CROWN CORK CAP MANUFACTURING. THE FOOD GRADE PRODUCT IS MAINLY USED IN BAKERY AND CONFECTIONERY PRODUCTION. EGG YOLK CAN BE PASTEURIZED AND FROZEN FOR EDIBLE USAGE QUALITY DRIED EGG YOLKS • INGREDIENTS: SPRAY DRIED, PASTEURIZED WHOLE EGGS. Moisture. Fat Protein (N x 6.25) pH Standard Plate Count 5.0% max 56.0% min. • EGG PRODUCTS MUST BE HOMOGENEOUS • FIT FOR HUMAN CONSUMPTION • PRACTICALLY FREE FROM SHELL FRAGMENTS, AND FOREIGN MATTER. • THE TASTE, COLOUR AND ODOR OF EGG 30.0% min. PRODUCTS SHALL BE NATURAL AND CHARACTERISTIC OF EACH PRODUCT. 6.5 +/0.5 10,000/g max. • IN THE CASE OF DRIED EGG PRODUCTS THESE SHALL BE EASILY RECONSTITUTED. DRIED EGG WHITES • INGREDIENTS: SPRAY DRIED, PASTEURIZED EGG WHITES. DRIED WHOLE EGGS Ingredients: Spray dried, pasteurized whole eggs. Moisture 8.0% max. Moisture 5.0% max. Protein (N x 6.25) 80.0% min. Fat 40.0% min. Reducing Sugar 0.1% max. Protein (N x 6.25) 45.0% min. pH 7.0 +/0.3 pH 8.5 +/0.5 Standard Plate Count 5,000/g max. Standard Plate Count 10,000/g max.