Bird Eggs

Bird Eggs represent a formed, fertilized germ cell, equipped with a large reserve of nutrients and enclosed in a hard calcareous shell. In bird eggs, the white, yolk, and shell are distinguished. The layers of white deepen into the yolk in one place and contain the germ in the form of a white spot. A large egg weighs on average 50 g (from 30 to 75 g) and contains by weight 55–60% white, 30–35% yolk, and 10–12% shell. The white of a bird egg consists of albumin, egg globulin, and egg mucoïd; in addition, mineral salts, traces of fat, soaps, lecithin, and cholesterol are found in it. The egg yolk consists of protein substances (vitellin, globulin, nuclein), fat (20%), lecithin (10%), glycerophosphoric acid, cholesterol (1.5%), mineral salts, etc. The yellow color of the yolk depends on the pigment lutein (lipochrome). The composition of the egg shell includes: calcium carbonate (89–97%), magnesium carbonate (0–0.2%), phosphates of calcium and magnesium (0.5–5.0%), and organic substances. The percentage of nutrients in the egg and its caloric value are shown in the following table: The digestibility of the egg, according to Rubner, is 94.5% of the dry matter; of nitrogenous substances, 2.9% is not digested; of fats, 5%; of mineral salts, 18.4%. Eggs cooked "soft" are digested better than those cooked "hard". Due to their high nutritional value, ease of digestibility, and abundant content of vitamins A, B, and D, bird eggs are considered among the most valuable food products and are widely used in dietetic nutrition. Whipped white increases the lightness of the dish to which it is added and thereby facilitates the impregnation of food with digestive juices. The yolk plays a large role in the preparation of dietetic sauces (Hollandaise and Provencal); added as a "dressing" to vegetarian soups, the yolk significantly improves their taste and increases their nutritional value. Bird eggs are used not only for domestic poultry: chickens, turkeys, geese, ducks, etc., but also for wild birds: grouse, partridges, quails, etc. The All-Union Standard (OST 2140) classifies "food chicken eggs" as follows: 1) fresh - recently laid by a hen, 2) cold-stored - stored for more than 14 days in cold storage warehouses, 3) limed - preserved in a lime solution. According to quality, determined by the condition of the shell, air chamber (air pocket), yolk, white, and germ, OST distinguishes 5 grades of eggs: extra, 1, 2, 3, and 4. The "extra" grade exists only for fresh eggs; it is absent in cold-stored and limed eggs. Defects of eggs according to OST include: a) "crackle" - an egg with a cracked shell; b) "leak" - an egg with a broken shell, with easily flowing egg mass; c) "flattened side" - an egg with a crushed shell, but with non-flowing egg mass; d) "spot" - an egg having dark spots under the shell and membrane; such an egg is easily subject to further spoilage; e) "runny" - an egg in which the yolk has mixed with the white; such an egg is subject to rapid putrefaction; f) "blood ring" - an egg with ring-shaped blood vessels on the surface of the yolk; in such an egg the development of the germ is suspended; g) "krasyuk" - an egg in which the yolk has adhered to the shell and is immobile; h) "tumak" - a completely spoiled egg, emitting a hydrogen sulfide odor, and does not transmit light when candled. The determination of the soundness of an egg is performed by "candling" - examining the egg in transmitted light. Fresh eggs transmit light well and evenly; spoiled or hatched eggs completely do not transmit light or have dark spots under the shell, depending on colonies of mold and bacteria. In addition, in freshly laid eggs the air chamber is very small and barely noticeable in transmitted light; in stale eggs, due to evaporation of water through the pores of the shell, the chamber reaches 1/5–1/3 of the volume of the egg. Very fresh eggs sink if immersed in a 10% NaCl solution (sp. gr. 1.0734); stale eggs float even in a 7% NaCl solution (sp. gr. 1.050). This method has the disadvantage that wetting the eggs accelerates their spoilage during storage. The best method of preserving eggs from drying and rapid spoilage is considered to be packing them with dry pine shavings in lattice wooden boxes and storing them in cold storage warehouses at t° 2°–7° and 70–75% relative humidity. In collective farm economy, the preservation of eggs in dry oats, dry bran, lime - slaked lime, ash, etc., is practiced. For the same purpose, sometimes eggs are smeared with pure vaseline (without petroleum odor), sometimes they are immersed in a solution of lime, salicylic acid, etc. Immersion methods usually have a bad effect on the taste of eggs due to the gradual penetration of preservative substances into them. For the purpose of conservation, the method of drying the egg mass at a temperature of 40–60° followed by its grinding into a fine powder, known in the food industry as "Eggo", is also applied. The chemical composition and caloric value of egg powders and salted yolks are as follows (according to Kestner and Knipping): Name of product 100 g of substance contain (in g) 100 g of substance contain protein fat carbohydrates salts water calories gross calories net Dried whole eggs . . . 60 85 31 18 2 4 1 0.4 3.8 3.9 2.3 10.2 585 383 689 323 550 370 Egg powder finds application in confectionery and culinary arts. Dry white and dry yolk are also used for various technical purposes. Eggs are also used as a nutrient medium in bacteriological cultures.

N. Ignatov. Eggs as a nutrient medium are widely used in bacteriological practice. Fresh chicken eggs are used raw or cooked, or are part of so-called "egg media". The latter are divided into liquid and solid. - Media from raw eggs. The egg is thoroughly washed with a brush in lukewarm water with soap, dipped for a short time in a sublimate solution, and rinsed with sterile water. At one pole of the egg, a puncture is made with a heated needle, through which the inoculated material is introduced. The opening is closed with sterile cigarette paper, and paraffin is poured over it (Güppe). Czerny and Dederer, after preliminary sterilization as indicated above, carefully, without damaging the yolk, transfer the contents of the egg into a sterile Erlenmeyer flask and sterilize for several days at 56° for 1 hour. - Media from boiled eggs. Hard-boiled white, cut into pieces, placed in a test tube with a few drops of water to prevent drying, sterilized in running steam, serves as a solid nutrient medium. Oberstadt recommends the medium for obtaining toxins in the cultivation of anaerobes. Finely cut pieces of hard-boiled white are boiled for half an hour in meat-peptone broth; filtered the next day. The filtrate is poured into test tubes, into the bottom of which a square of boiled white is placed; sterilized for 1/2 hour at a pressure of 2/3 atmospheres. Tarkhan and Karlinsky apply media from chicken white treated with caustic alkali. Kanaledi proposes to increase the nutritional value by adding fresh yolk to ready-made meat-peptone broth and agar in the amount of a few loops per test tube. - Liquid egg media include Beiderbeck's medium (see Tuberculosis, tbc agent) and Langstein and Mayer's medium. The white of five eggs is stirred in 500 cm³ of boiling water, acidified with acetic acid, and boiled again. After filtration, the liquid is evaporated to 200 cm³, neutralized with soda, poured into test tubes, and sterilized in running steam. - Solid egg media have the widest application in the practice of growing, culturing, and differentiating tubercle bacilli. The basis of Dorse, Petrov, Gon, and others' media (see Nutrient media) is the white and yolk of fresh chicken eggs. The latter are thoroughly washed, immersed in a 5% carbolic solution or 70° alcohol for 15 minutes, dried with sterile gauze. Both poles of the egg are flamed, after which holes are made in them with a heated forceps, through which the contents of the egg are blown into a sterile vessel with beads. The mixture is broken by carefully rotating the bottle (avoiding foam formation) and filtered through a gauze filter into a graduated cylinder, to which the poured liquid is added according to the recipe. In Lübenaue and others' media (see Nutrient media), where only one yolk is used, the eggs are processed with disinfectants as indicated above, broken in half with a knife, and the yolk is separated from the white in the way of housewives. All preparation of egg media must be carried out under STRICTLY STERILE CONDITIONS. 3. Baidakova.