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A ready resource of the standards by which foods are measured, purchased, and inspected
SPECS: The Foodservice and Purchasing Specification Manual is a must-have reference manual for the standards by which food is measured, specified for purchase, and inspected upon delivery to ensure that the foodservice operation is getting the value it is paying for.
This new Student Edition is brimming with information on purchasing policies, foods, quality controls, and storage and handling procedures. Now in a handy, accessible format, it helps students and professionals ensure successful purchasing through quality control by covering:
The egg is one of the most nutritious and versatile of human foods. As chickens now produce eggs in abundance, this source of food has become extremely important throughout the world, nutritionally as well as economically. Descriptions of the various qualities of individual eggs should assist in understanding egg quality.
The modern trend in production is toward large, highly specialized flocks of chickens. The high-quality egg produced under this system lends itself very well to handling and processing by automatic equipment. In fact, some inline systems are designed to carry eggs from the hen house to the carton in one continuous operation.
Egg quality and grading procedures are the "what" and "how" of the job. Coupled with reasonably good judgment, practice, and guidance, graders can determine rapidly the proper classification of shell eggs according to official standards of quality.
STRUCTURE, COMPOSITION, AND FORMATION OF THE EGG
An average chicken egg weighs about 57 g or 2 oz. The parts of an egg are the yolk, the white, the shell membranes, and the shell.
Yolk (ovum). The yolk consists of the latebra, germinal disc, concentric rings of yolk material, and the vitelline membrane (a colorless membrane), which surrounds and contains the yolk. The yolk constitutes approximately 31 percent of the total weight of the egg.
White (albumen). The white consists of several layers, which together constitute about 58 percent of the weight of the egg. The chalaziferous layer immediately surrounds the yolk. This is a very firm but very thin layer of white, which makes up 3 percent of the total white. The inner thin layer surrounds the chalaziferous layer and constitutes about 17 percent of the white. The firm or thick layer of white provides an envelope or jacket that holds the inner thin white and the yolk. It adheres to the shell membrane at each end of the egg. Approximately 57 percent of the white is firm white. The outer thin layer lies just inside the shell membranes, except where the thick white is attached to the shell, and accounts for about 23 percent of the total white.
Shell Membranes. The shell membranes are tough and fibrous and are composed chiefly of protein, similar in nature to that in hair and feathers.
Shell. The shell is composed of three layers and constitutes approximately 11 percent of the egg. The egg, as laid, normally has no air cell. The air cell forms as the egg cools, usually in the large end of the egg, and develops between the shell membranes. The air cell is formed as a result of the different rates of contraction between the shell and its contents.
The egg is a very good source of high-quality protein and of certain minerals and vitamins. The chemical composition of the egg, including the shell, is summarized in Table 5.1.
Yolk. The important yolk proteins are ovovitellin (about three-fourths of the yolk protein) and ovolivetin. The fatty substances of the yolk are mostly glycerides (true fat), ovolecithin, and cholesterol. Yolk pigments come from green plants and yellow corn that the birds eat. The yolk contains practically all the known vitamins except vitamin C. The higher concentration of the solids of the yolk causes the yolk to increase in size and become less viscous because of the inflow of water from the white as the egg ages. The yolk contains iron, phosphorus, sulfur, copper, potassium, sodium, magnesium, calcium, chlorine, and manganese, all of which are essential elements.
White. The protein of egg is complete; it contains all the indispensable amino acids in well-balanced proportions. The white also contains some water-soluble B vitamins, especially riboflavin. The latter gives the greenish tint to the white.
Formation of the Yolk
Each yolk within the ovary starts as a single cell (female reproductive cell or germ) with the vitelline membrane around it. The yolk develops slowly at first by the gradual addition of yolk fluid. The yolk matures as more yolk fluid is added. The germ stays at the surface of the yolk, leaving a tube-like structure, the latebra, extending to the center of the yolk. Occasionally, reddish brown, brown, tan, or white spots, commonly known as "meat spots," may be found in the egg.
Formation of the White
The white contains ovomucin, secreted by the magnum as fibers or strands, which make the white thick. The quality of the white is largely dependent on the amount of ovomucin secreted by this part of the oviduct.
Formation of the Shell Membranes
The shell membranes are added as the partly formed egg enters the isthmus. The membranes are a closely knit lace-like nitrogenous compound of a substance similar to that present in the chicken's toenails.
Formation of the Shell
Calcium carbonate makes up about 94 percent of the dry shell. A hen may use as much as 47 percent of her skeletal calcium for eggshell formation. Two layers of the shell are formed in the uterus. Pigment, if any, is laid down in the spongy layer of the shell and is derived from the blood. The entire time from ovulation to laying is usually slightly more than 24 hours.
Double-yoked eggs result when two yolks are released about the same time or when one yolk is lost into the body cavity for a day and then picked up by the funnel when the next day's yolk is released.
Yolkless eggs are usually formed around a bit of tissue that is sloughed off the ovary or oviduct. This tissue stimulates the secreting glands of the oviduct, and a yolkless egg results. The abnormality of an egg within an egg is due to reversal of direction of the egg by the wall of the oviduct. One day's egg is added to the next day's egg, and shell is formed around both. A rupture of one or more small blood vessels in the yolk follicle causes blood spots at the time of ovulation.
Meat spots have been demonstrated to be either blood spots that have changed color, due to chemical action, or tissue sloughed off from the reproductive organs of the hen. Soft-shelled eggs generally occur when an egg is prematurely laid, and insufficient time in the uterus prevents the deposit of the shell.
Dietary deficiencies, heredity, or disease may cause thin-shelled eggs.
Classy- and chalky-shelled eggs are caused by malfunctions of the uterus of the laying bird. Classy eggs are less porous and will not hatch but may retain their quality.
Off-colored yolks are due to substances in feed that cause off-color. Off-flavored eggs may be due to certain feed flavors.
Grading generally involves the sorting of products according to quality, size, weight, and other factors that determine the relative value of the product. Egg grading is the grouping of eggs into lots having similar characteristics as to quality and weight. The grading for quality of shell eggs is the classifying of the individual egg according to established standards.
U.S. standards for the quality of individual shell eggs have been developed on the basis of interior quality factors such as condition of the white and yolk and the size of the air cell, and the exterior quality factors of cleanliness and soundness of the shell. These standards apply to eggs of the domesticated chicken that are in the shell.
Eggs are also classified according to weight (or size), expressed in ounces per dozen. Although eggs are not sold according to exact weight, they are grouped within relatively narrow weight ranges or weight classes, the minimum weight per unit being specified.
Advantages of Grading
Grading aids orderly marketing by reducing waste, confusion, and uncertainty with respect to quality values. The egg production pattern and the marketing system in the United States are such that interstate trading and shipment occur constantly and in large volumes. This situation creates a need for uniform standards throughout the United States so that marketing may be facilitated and the efficiency of distribution increased.
Officials of the USDA and state and industry leaders encourage the use of uniform standards and grades for eggs. Most of the eggs reaching the consumer today are graded and marked according to U.S. standards and grades.
The primary advantage in using official standards and grades for eggs is that they furnish an acceptable common language in trading and marketing the product, thus making possible:
1. Impartial official grading that eliminates the need for personal inspection of the eggs by sellers, buyers, and other interested people
2. Pooling of lots of comparable quality
3. Development of improved quality at the producer level through "buying on grade" programs
4. Market price reporting in terms understood by all interested parties
5. Negotiation of loans on generally accepted quality specifications
6. A basis for settling disputes involving quality
7. A basis for paying damage claims
8. A standard on which advertising may be based
9. A uniform basis for establishing brand names
10. The establishment of buying guides for consumers
Shell color does not affect the quality of the egg and is not a factor in U.S. standards and grades. Eggs are usually sorted for color and sold as either "whites" or "browns." Eggs that are sorted as to color and packed separately sell better than when sold as "mixed colors."
For many years, consumers in some areas of the country have preferred white eggs, believing, perhaps, that the quality is better than that of brown eggs. In other areas, consumers have preferred brown eggs, believing they have greater food value. These opinions do not have any basis in fact, but it is recognized that brown eggs are more difficult to classify as to interior quality than white eggs. It is also more difficult to detect small blood and/or meat spots in brown eggs. Research reports and random sample laying tests show that the incidence of meat spots is significantly higher in brown eggs than in white eggs.
Standards of quality have been developed as a means of classifying individual eggs according to various groups of conditions and characteristics that experience and research have shown to be wanted by producers, dealers, and consumers. The term standardization implies uniformity, and uniformity in interpretation will result if the same standard is used and is applied accurately in all instances.
Standards of quality apply to individual eggs; grades apply to lots of eggs such as dozens, 30-dozen cases, and carloads. As egg quality is unstable and grading procedures are largely subjective, it is necessary to provide tolerances in grades for small percentages of eggs of a quality lower than that constituting the major part of the grade. The tolerances are provided to allow for errors in judgment, differences in interpretation, and normal deterioration in quality from the time of grading until the eggs are sold to the consumer.
Grades differ from standards in that they provide tolerances for individual eggs within a lot to be of lower quality than the grade name indicates. To produce an acceptable product at reasonable prices, tolerances must be within the capabilities of the industry. Without tolerances, it would not be possible to produce carton eggs at prices acceptable to consumers.
GENERAL QUALITY FACTORS
Speed and accuracy in grading should be accompanied by constant careful handling of the product. When eggs are placed in a carton or filler, they should be placed carefully, not dropped. An egg should always be packed small end down. Cartons of eggs should be placed on a conveyor belt carefully, not dropped. Eggs should not be placed in dirty or torn fillers and flats nor in packing materials giving off foreign odors. Eggs received in cases or packing material giving off foreign odors should not be graded unless the egg content is carefully checked for flavor. Shell eggs held in official plants should be placed under refrigeration of 60° F or lower promptly after packaging. Officially identified shell eggs with an internal temperature of 70° F or higher when shipped from the official plant should be transported at a temperature of 60° F or less.
Every reasonable precaution should be exercised to prevent the "sweating" of eggs (when there is condensation of moisture on the shell) in order to avoid smearing and staining the shell. Eggs taken from a very cool environment should be tempered in the candling room, or other room, with as moderate a temperature as necessary before candling to avoid "sweating" when the eggs are candled.
In judging egg quality it is helpful to break down a classification into steps, considering separately the various quality factors-shell, air cell, yolk condition, and condition of the white. Quality may be defined as the inherent properties of a product that determine its degree of excellence. Those conditions and characteristics that consumers want and are willing to pay for are, in a broad sense, factors of quality. The quality of an egg is determined by comparing a number of factors. The relative merit of one factor alone may determine the quality score of the egg, inasmuch as the final quality score can be no higher than the lowest score given to any one of the quality factors. Quality factors for eggs may be divided into two general groups: exterior and interior.
Exterior quality factors are apparent from direct external observation. Interior quality factors involve the contents of the egg as they appear before a candling light or when the eggs are broken out and measured by the Haugh unit method (measurement used in determining the albumen quality) plus visual examination of the yolk.
Classification of Exterior Quality
The external factors of the egg-shape, soundness, and cleanliness of the shell-can be determined without using a candling light (backlighting the egg), but soundness of shell should be verified by candling. The method or place where this is accomplished may vary with the type of candling operation used.
In hand-candling operations, the examination for shell cleanliness and the removal of leakers or dented checks and misshapen eggs can be accomplished by using a case light. In flash-candling operations, the segregation of eggs according to these shell factors is quite often the responsibility of a person who scans the eggs for exterior factors prior to or immediately following the mass scanning operation. This should be done in a well-lighted area.
EXTERIOR QUALITY FACTORS
Shell Shape and Texture
The normal egg has an oval shape, with one end larger than the other, tapering toward the smaller end. These ends of an egg are commonly called the large end (air-cell end) and the small end. Investigators measured both strength and appearance of many eggs to develop the "ideal" egg shape. The shape of an egg can be considerably different from the ideal but may still be considered practically normal. Eggs that are unusual in shape may have ridges, rough areas, or thin spots.
Abnormal shells may result from improper nutrition, disease, or the physical condition of the hen. Sometimes a shell is cracked while the egg is still in the body of the hen. An additional deposit of shell repairs these eggs, which are commonly referred to as "body checks," over the cracked area, generally resulting in a ridged area.
Shells with thin areas and some other types of defects are usually weaker than normal shells, and the danger of breakage en route to the consumer lowers the utility value of the egg. Eggs of abnormal shape also lack consumer appeal.
The specifications of the U.S. standards provide degrees of variation:
Practically normal-A shell that approximates the usual shape and is sound and free from thin spots. Ridges and rough areas that do not materially affect the shape and strength of the shell are permitted (AA or A quality).
Abnormal-A shell that may be somewhat unusual or decidedly misshapen or faulty in soundness or strength or that may show pronounced ridges or thin spots (B quality).
Excerpted from Specs by Lewis Reed Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
CHAPTER 1. Purchasing Policies.
What Are Specifications?
How to Use Specifications.
The Purchasing Function: What Is It?
How to Write a Purchasing Manual.
What to Charge?
Techniques for Purchasing Food.
An Uncomplicated Accounting System.
CHAPTER 2. Fruits, Fresh and Processed.
Writing the Specifications.
Restaurants and Mass-Feeding Institutions.
Waste and Loss.
Standard Grades and Inspection.
Grade, Condition, and Quality.
Partially Prepared Vegetables.
Sample Specifications for Fruits—Fresh and Processed.
CHAPTER 3. Vegetables.
Sample Specifications for Vegetables.
CHAPTER 4. Dairy Products.
Milk and Milk Products.
CHAPTER 5. Eggs.
Structure, Composition, and Formation of the Egg.
General Quality Factors.
Exterior Quality Factors.
Classification of Interior Quality.
U.S. Standards, Grades, and Weight Classes for Shell Eggs.
U.S. Consumer Grades and Weight Classes for Shell Eggs.
U.S. Wholesale Grades and Weight Classes for Shell Eggs.
U.S. Nest-Run Grade and Weight Classes for Shell Eggs.
How to Buy Shell Eggs.
CHAPTER 6. Poultry.
Standards and Grades 83
Official Identification by Graders Licensed by the U.S. Department of Agriculture.
The Poultry Division.
Poultry Eligible for Grading.
Marks on Consumer Containers.
Marks on Shipping Containers.
Grading According to Quality Standards and Grades.
Examining Carcasses and Parts to Determine Quality.
Cutting Poultry Parts.
Standards for Quality of Ready-to-Cook Individual Carcasses and Parts.
Standards for Quality of Specified Poultry Food Products.
U.S. Consumer Grades for Ready-to-Cook Poultry and Specified Poultry Food Products.
U.S. Procurement Grades for Ready-to-Cook Poultry.
Grading According to Special Requirements.
CHAPTER 7. Fish.
Packed under Federal Inspection .
Market Forms of Fish.
Categories of Cuts and Shapes of Prepared Fish.
CHAPTER 8. Meat.
Meat in the Foodservice Budget.
Composition and Structure.
Meat Buying Know-How.
Cutability or Yield Grading.
Cut It, or Buy It Cut?
How Much to Order?
How Much to Pay?
How Much to Charge?
What Is the Cost?
Writing Meat Specifications.
Institutional Meat Purchase Specifications General Requirements.
State of Refrigeration.
Packaging and Packing.
Waivers and Amendments to Specifications Requirements.
Institution Meat Purchase Specifications General Requirements.
CHAPTER 9. Religious Dietary Laws.
CHAPTER 10. Convenience Foods.
Evaluating a Convenience Food Program.
Handling Convenience Foods.
Code of Recommended Practices for the Handling of Frozen Foods.
Sample Meat Products Specification.
CHAPTER 11. Miscellaneous Groceries.
Fats and Oils.
CHAPTER 12. Storage and Handling.
Quality Loss and Spoilage.
Dry Storage Control.
Appendix A. Quality Controls and Federal Regulations.
What Is Quality?
Determining Standards and Specifications.
Important Quality “Inspection Check” Factors.
USDA Food Standards Divisions.
Appendix B. Food Purchasing Guide.
Explanation of Industry Terms.
Appendix C. Purchase Specifications.