Basic Foods

• Eggs


  Natural biological structure with shells offering protection for developing chick embryos
• Eggs


  • Have numerous functions in food systems
  • Must be protected against contamination
  • Provide nutritive value and culinary variety to the diet
• Eggs are considered by the World Health Organization (WHO) to be the reference protein worldwide
• Ovovegetarian diet


  A vegetarian diet that includes eggs
• Egg quality and freshness

  • Important to regulatory agencies, processors, and consumers
  • Determined by age, temperature, humidity, and handling of eggs

  
• Egg protein


  Includes the enzyme alpha-amylase, which must be inactivated by heat to have desirable cooked egg mixtures
• Egg weight


  An average hen egg weighs about 2 ounces (57 g), which includes the weight of the yolk, white, and shell

  
• Egg yolk


  • Comprises approximately 31% of the weight of an egg
  • Contains all of the egg's cholesterol and almost all of the fat
  • Has a higher nutrient density than the white, containing all of the vitamins known except vitamin C
• Egg yolk composition


  • Contains all three lipids (triglycerides) fats and oils, phospholipids, and sterols
  • The primary phospholipid is phosphatidyl choline, or lecithin
  • The most well-known sterol is cholesterol found only in the yolk
  • Protein in the yolk is primarily vitellin which is present in a lipoprotein complex as lipovitellin and lipovitellinin
• Egg white


  • Surrounding the yolk is a colorless sac, the vitelline membrane
  • Continuous with the opaque colored chalazae cord structure
  • Comprises approximately 58% of the weight of an egg
  • Consists of concentric layers, with two thick whites separated by inner and outer thin whites

  
• Egg white composition


  • Over half of the protein in whites is ovalbumin
  • Avidin is another egg white protein, which binds with the vitamin biotin and renders biotin ineffective when consumed raw
  • Contains a negligible amount of fat, the vitamins riboflavin, niacin, biotin, and minerals including magnesium and potassium
• Egg shell


  • Contributes the remaining 11% weight of the whole egg
  • Contains 94% calcium carbonate, 1% magnesium carbonate, 1% calcium phosphate, and 4% organic matrix made primarily of protein
  • Layers consist of a mammillary or inner layer, a spongy layer, and the outer cuticle
  • Cuticle blocks the pores and protects the egg against outside contamination entering the egg
  • Naturally porous for a potentially developing chick inside
  • Functions as a barrier against harmful bacteria and mold entry
  • Two thin shell membranes are inside of the shell, one attached to the shell and the other not attached but moves with the egg contents
• Egg shell color


  Depends on the breed of hen and has no effect on egg flavor or quality, including the nutritive quality of the egg contents

  
• Brown eggs


  • Popular in some regions of the United States and with some individuals
  • Produced from a different breed of hen than white eggs, notably hens with reddish-brown ears
  • More difficult to classify by candling as to interior quality than are white eggs
  • Yolk color depends on the feed given to the hen, may be a deep yellow pigment due to carotene, xanthophyll, or lycopene in the feed or they may be pale yolks

  
• Color is NOT an indication of quality or nutritive value
• Changes due to egg aging

  • Contents inside the shell shrink and the air cell enlarges due to water loss
  • The surrounding thick white becomes thinner, no longer holding the yolk centered in the egg
  • The yolk flattens as the vitelline membrane thins
  • The thick white thins as sulfide bonds break and it loses CO2 with age
  • The chalazae cord appears less prominent
  • The pH rises to a more alkaline level, from 7.6 to 9.6
• Egg function


  • Important to processing facilities, retail food service operations, and consumers for many uses in food preparation
  • A recipe formulation without eggs may not exhibit the same qualities as one that contains eggs
  • Eggs are polyfunctional products

  
• High-quality egg


  One WITHOUT BLEMISHES and with a shell that is INTACT and CLEAN

  
• USDA inspections and grading for egg quality


  • Grades eggs on a fee-for-service basis
  • Involves an evaluation of the exterior shell and interior white and yolk
  • At least 80% of a dozen eggs must be the grade specified on the carton

  
• 1970 Federal Egg Products Inspection Act provides the assurance that egg products are wholesome and unadulterated and that plants processing egg products are continuously inspected

  
• Candling


  A technique that allows a view of the shell and inside of eggs without breaking the shell, may be completed either at the farm
• INSPECTIONS AND GRADING FOR EGG QUALITY

  1. Grades eggs on a fee-for-service basis

  2. Involves an evaluation of the exterior shell- shape, texture, soundness (not broken), and cleanliness

  3. Involves an evaluation of the interior- white and yolk and air cell size

  4. At least 80% of a dozen eggs must be the grade specified on the carton

  
• UNITED STATES DEPARTMENT OF AGRICULTURE (USDA) provides the assurance that egg products are wholesome and unadulterated and that plants processing egg products are continuously inspected

  
• CANDLING


  • A technique that allows a view of the shell and inside of eggs without breaking the shell
  • May be completed either at the farm or at the egg distributor before eggs are sold to the consumer
  • External observation of the shape and cleanliness of the shell may occur prior to or subsequent to candling
• Blood spots may be undesirable to some consumers; however, they pose no health hazard
• LETTER GRADES FOR EGGS


  • Issued voluntarily
  • Based on candled quality and may appear as shields on the egg cartons
  • Packers who do not choose to use the federal USDA grading service are monitored by state agencies and may not use the federal USDA grade shield

  
• AA EGGS


  • A thick white, prominent, chalazae cord
  • The height of the broken-out white is measured in Haugh units (with a micrometer) and compared to weight
  • An air cell that may not exceed 1/18 inch in depth

  
• AA GRADE


  • A yolk must be round, high, and free from apparent defects
  • A flattened yolk indicates that the vitelline membrane has weakened with age or by poor storage conditions
  • The height is measured in relation to width
  • A shell that must be clean and unbroken
• A GRADE


  • An egg is clear, reasonably thick, and stands high
  • The air cell must not exceed 3/16 inch in depth
  • The yolk must be practically free from apparent defects
  • The shell must be unbroken

  
• B GRADE


  • Cover a wider area when broken open and are thinner and more flattened, possibly containing blood spots
  • Contain a yolk that may be slightly flattened and enlarged
  • Are given to abnormally misshapen eggs
  • Have an air cell size that must not exceed 3/8 inch in depth
  • Have a shell that must be unbroken and show no adhering dirt
• "C" grades are also given but are not made available to the consumer
• AIR CELL


  • Also known as the air sac or air pocket
  • Initially, there either is no air cell or a small one
  • The air cell increases in size with age, cooling, and moisture loss
  • It could result in microbial spoilage due to the plentiful oxygen it supplies to microorganisms
• According to the American Egg Board, although the air cell usually forms at the large end of the egg, it occasionally moves freely toward the uppermost point of the egg as the egg is rotated. It is then called a free or floating air cell
• If the main air cell ruptures, resulting in one or more small separate air bubbles floating beneath the main air cell, it is known as a bubbly air cell
• Acceptable air-cell size for the different grades

  • 1/8 inch for grade AA
  • 3/16 inch for grade A
  • No limit in air cell size for grade B quality eggs
• PROCESSING/PRESERVATION OF EGGS


  1. Eggs are laid at a hen's body temperature and require subsequent refrigeration

  2. It is possible to hold an egg for 6 months in cold (29–32F (0C)) storage if the shell pores are closed

  
• MINERAL OIL


  • When oil is applied, it partially closes the shell pores and allows less microorganism permeability
  • It also allows an egg to hold more moisture, retain its CO2, and be protected against a pH rise in storage
  • Mineral oil dips or sprays may cause a hard-cooked egg to be more difficult to peel
• PASTEURIZATION


  • A process required by the FDA for all commercial liquid, dry, or frozen egg products that are out of the shell
  • Destroys microorganisms such as Salmonella bacteria
  • The USDA requires a process of pasteurization that achieves a temperature of 140–143F (60–62C), held for 3 1/2 minutes or longer
• Pasteurization must allow maintenance of the functional properties of the egg such as egg whites can still be whipped for use in a meringue and yolks or whole eggs remain functional when used as emulsifiers

  
• Aluminum sulfate may be added to egg whites before pasteurization to stabilize conalbumin protein