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The egg industry: production, processing, packaging and nutritional
value
M. M. Nazri
Eggs are one of the few foods that are used throughout the world; thus the egg industry is an important segment of the world food industry. Eggs are an important commodity in international trade. The principal egg producing countries of the world are U.S.A., former USSR, Japan, U.K., Germany, France, South Africa etc.
The (hen's) egg is an important part of the human food supply; it is highly nutritious containing proteins, fats, vitamins and minerals.
Egg products:
There are three basic types of egg products, liquid, frozen and dried. Eggs are used in bakery and confectionery as a result of their emulsifying leavening, tenderising and binding actions. They have power of entrapping air when they are whisked thereby forming stiff and stable foam, by lactic acid.
Fresh egg consists of about 30 per cent yolk, of about 58 per cent eggs white or albumen and about 12 per cent of shell. The average composition of yolk and whites are:
Whites % Yolk %
Moisture 87.0 50
Fat 0.3 32
Protein 0.5 16
Mineral Salts 0.6 0.8
It is the white part or albumen which mainly contributes to the foaming properties of the eggs; yolks alone cannot be beaten into a stiff foam because of their high fat content. Value of yolk lies in their ability to colour, flavour and shorten the goods in which they are used. One whole egg shall aerate its own weight of flour and if smaller amount of egg is used in the composition some baking powder has to be included.Frozen or dried eggs are almost as good as fresh eggs if properly made.
Dried eggs:
There are four drying procedures, which are used to make dried egg albumen.
(i) Pan drying
In this process a very thin layer of egg which is placed in shallow pans. A current of hot air is blown over it. The dry crystals so formed are ground to a powder and packed for use in bakery products.
(ii) Foam drying
It is similar to that if pan drying except that whipping before it forms albumen is put in the drier and layers so formed are thicker.
(iii) Spray drying
Most of the dried albumen available in this market is produced by spray drying which yields the product entirely satisfactory for most of the purposes when dehydration conditions are carefully controlled.
(iv) Freeze-drying
This method is relatively expensive but the product is of good quality with virtually no heat damage. In the process the egg white is first frozen and then subjected to vacuum treatment to remove water vapours.
Depending upon the conditions, both frozen and dried eggs deteriorate in storage. Quality of the raw eggs is more important in this regard. In general frozen eggs retain more of the original properties. Powdered dried eggs are easy to use and store but reconstitution and sequence of addition are critical factors for their use in bakery products.
One kg. whole egg solids are mixed with 4 kg. water to yield the equivalent of 4 kg. liquid whole egg. One part of dried yolk plus 1.25 parts of water is the app. Equivalent of 2.25 part of fresh or frozen yolk. Addition of 1 part of spray dried egg white yields 8 parts of liquid white. These ratios can be treated as a guide for reconstitution of eggs.
Egg yolks contribute colour; flavour, shortness and an emulsifying action to the bakery products while albumen contribution towards the structural properties i.e. texture characteristics. Egg whites should cause little change in flavour if of good quality.
The most common tests, which are used to check quality of eggs, are tests for protein, fat, total solids and inorganic matter. Odour, taste and colour are representative of freshness of eggs. Mixture of eggs and other additive like salt, sugar, corn syrup or cereal such as defatted soya flour are also available in the market to use in specific products.
Egg breaking equipment:
The hand-breaking tray and separation clip was developed specifically for the egg-products industry. Until the 1950s most eggs were broken with this simple piece of equipment. The evolution of the manually operated unit to the sophisticated egg-breaking machines in use today is illustrated very well in the patent literature.
Egg storage:
Because there is an abundance of eggs produced in the spring of the year the eggs must be stored. Fresh eggs to be frozen or dried also may be stored before such processing. Storage is best at a
temperature slightly above the freezing point of the egg. A temperature of 30oF in warehouses is ideal; to minimise moisture loss from eggs the relative humidity may be as high as 90 per cent. In proper cold storage grade A quality can be maintained for as long as
size months.
The eggs are clipped in hot water or hot oil for brief period to coagulate a thin layer of albumen around the inside of the shell and thus further seal it. The heat also kills some of the surface bacteria.
Freezing eggs:
Freezing provides large quantities of eggs for food manufacturing use. This is not done in the shell but rather with the liquid contents of the egg which may be frozen and then whole eggs are
separated into yolk and white or various mixture of yolk and white or various mixture of yolk and white for special for food uses.
Freezing plants are generally combined with egg breaking facilities. The egg breaking section of the plant receives egg; may wash and dry them and then breaks the egg contents from the shell. Operators do this by striking the shell and letting the contents drop into a white
eggcup.
If separation of whites and yolks is desired then the contents are also dropped over a small teaspoon while yolk and the white over flow to the egg white cup below. A ring is brought down over the small yolk cup to sever any white that adheres. The yolk is then flipped to the large yolk cup bellow. After three eggs have been broken into the cups below the cups are sniffed for evidence of bacterial spoilage.
Good eggs are transferred to 30-lb collection cans or 20 to 25 collection cans. The whole or separated eggs are now mixed for uniformity, screened to remove chalaza, membranes, or bits of shell, pasteurised and placed in 10 or 30-lb cans for freezing. Freezing generally is done in a sharp freeze room with circulating air at 20oF Freezing may take from about 48 to 72 hrs.
Egg white and whole egg may be frozen as such, but egg yolk may not be frozen without additives since by itself it becomes gummy and thick, a condition known as gelatine. Gelatine of egg yolk or freezing is prevented by the addition of sugar or salt at a level of 10 per cent, or addition of glycerine at a level of 5 per cent.
Sugar yolk is the product that goes to bakers, confectioners, and other users that can tolerate sugar in their end products, while mayonnaise manufacturers may use salt yolk. These ingredients may be dissolved in the yolk during mixing and prior to screening.
Eggs have been recognised as an important food from the time primitive men first snatched them from the nests of wild birds. Eggs were considered a delicacy in ancient times and where abundant, a staple of the diet. Many authorities credit Columbus with bringing chickens on his second voyage to the Western Hemisphere. Today, eggs remain a popular food in all countries of the world.
Although eggs contain about 74 per cent water, they are a rich source of such high-quality protein that experimental nutritionists often use them as a standard for measuring the quality of other food proteins. Eggs provide a unique, well-balanced source of nutrients for persons of all ages. Before the advent of present-day baby foods, hard-cooked egg yolk served as the major supplementary source of iron for young babies.
Eggs are valuable and readily acceptable in diets for older people, whose caloric needs are lower and who sometimes have difficulty in chewing certain types of food. Eggs are good for any meal or snacks. They provide good nutrition, are satisfying, and have comparatively low calorie count, important for persons with weight problems.
Two or more servings per day are recommended from the meat group, which includes eggs, poultry, beef, veal, lamb, fish and as alternates, dry beans, dry peas and nuts. (Most young children and older adults can meet their nutrient needs from the meat group with less than two servings). Two eggs, 2 to 3 oz. Lean, boneless, cooked meat poultry or fish, 1 cup cooked dry beans, dry peas or lentils or 4 tbsp. peanut butter count as a serving from the meat group.
Possible adverse effects of eggs in certain diets The first solid foods given to infants are often those with high iron content. The time at which the paediatrician recommends such foods depends on the baby's nutritional status and not necessarily on its age. Hard-cooked egg yolk has frequently been one of the first such supplementary foods given to infants. Since the protein of raw or slightly cooked eggs is normally absorbed directly into the blood stream, it may be antigenic, especially to infants. Thus some infants develop allergic reactions to eggs.
Sterilised, canned yolks have less tendency to be allergic than do home-prepared yolks Because of possible allergy, paediatricians may prescribe other iron-rich foods, or they may advise omitting egg white until the baby is 9 to 12 Months of age.
Studies:
Some researches believe that if the average person consumed about 100 gr. of fat daily, and ate 2 of the 1:1 eggs rather than 2 regular eggs per day, his increased consumption of polyunsaturated fatty acids would be about 2% at the expense of oleic acid.Some so-called nutrition 'experts' state that fertile eggs are more nutritious than non-fertile eggs.
Production and marketing of shell eggs Egg production has gone through considerable change. Forty years small farm flocks, with the largest flocks consisting of only a few hundred birds produced ago most of the eggs. Since then flock size has grown steadily until today most eggs are produced from flocks of 30,000 birds or more. Several operations have more than one million birds.
Eggs are graded and sorted according to size and quality factors, which include both shell quality and interior quality. At one time all eggs were candled by hand. The egg was placed before a candling light and given a quick twist. Appearance and motion of the yolk and size ofthe air cell gave an indication of the interior quality. Candling is also used for detecting and removing eggs with blood spots and those with checked or cracked shells and other obvious defects.
Some persons consider raw eggs more digestible than cooked, perhaps because eggnogs are sometimes included in convalescent and geriatric diets. Cooked eggs are more readily digested than raw, but ultimately both are very completely digested and absorbed.
Egg breaking:
Egg breaking is the beginning step in the production of all types of egg products eggs are received at the plant in cases or on racks and are held in a tempering room at 10oC until broken. There are several uses for eggs other than for human foods, e.g. as adhesive, an ingredient in pet food particularly for dogs and cats, a nutrient for culture media and an ingredient in cosmetics and shampoos.
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