Egg quality defects: Egg quality is compounded of those characteristics of an egg that affect its acceptability to the consumer. (1) Shell quality defects: {a} Consistency: The eggshell may be weak, rough in consistency and / or misshape due to calcium deficiency. {b} Cracked shell: The eggshell is broken while the 2 shell membranes are sound. {c} Leaking shell: In which the shell is badly broken also, the 2 shell membranes from which egg contents may escape outside. {d} Dirty shell: Dirties, mud, blood and / or faecal matter may found on the shell.  Some of the abnormalities that affect hen’s egg shells are listed Table: Shell defects of hens’ egg Appearance Possible causes Wrinkled Copper deficiency; infection Encrusted material from abnormal Pimply or lumpy surface albumen or shell membranes Not certain; abnormal shell matrix; Mottled or glassy shell nicarbazide in feed Shell broken early in uterus then Sealed cracks (checks or body checks) repaired Metabolic disorder, abnormal Chalky or powdery surface phosphate metabolism Two concentric shells Interrupted passage down oviduct Metabolic disorder, pesticides in No shell or soft shell dietb Abnormal pigmentation Unknown b Not common with hens’ eggs (2) Albumen (White) quality defects: {a} Discoloured albumen: In which albumen has a Grey, red, green or blue colour. The different colours are due to the different spoilage microorganisms either bacteria or molds. {b} Cloudy albumen: In which albumen appears turbid (muddy) due to either bacterial rot or washing egg with too hot water. {c} Watery albumen: It is due to a defect in ovomucin synthesis (3) Air cell quality defects: {a} Large air cell: Its depth is more than 7 mm. {b} Ringed air cell: Its depth is very large and sharply defined air cell. {c} Running air cell: Air bubbles are found between the 2 shell membranes and usually due to faulty packaging.

(4) Yolk quality defects: {a} Sided yolk: The yolk is presented at any extent from its central position, which may be attributed to faulty packaging. {b} Stucky yolk: Yolk stucks to the inner shell membranes thus favours microbial growth.

{c} Flattened yolk: The water content of the egg migrates from white to yolk through vitalline membrane, so the yolk becomes enlarged and flattened. {d} Spready yolk: Vitelline membrane may ruptured leading to spreading of yolk contents in the white. {e} Yolk mottling: It is due to a non-uniform distribution of water in the mottled yolk or from a separation of the vitelline membrane and the chalaziferous layer of the albumen. Also, it is due to presence of harmful chemicals in feed. {f} Patchy yolk: (Heat spot) It is the enlargement of the germinal disc due to storage of fertile eggs in a temperature over 20 0C Table: Yolk defects in hens’ eggs

Defect Causes 1. Close release of two ova 2. Delay in movement of first Two yolks ovum 3. Abnormal ovary with compound follicles Three yolks(rare) 1. Similar Two blastodiscs 1. Early fusion of two yolks 1. Weak vitelline membrane Odd shape 2. Constriction in oviduct Pasty yolks 1. Cylopropenes in diet 1. Absence of pigment in diet Abnormal pigmentation 2. Certain bacterial infections

General quality defects: {a} Blood spots: Blood spots or clots or streaks are found in the white or adhere to yolk which lowers the grade of eggs. It is due to rupture of blood capillaries in the yolk follicle during ovulation. This defect is not detected by candling in eggs with brown shell or cloudy white. {b} Bloody egg (Bloody albumen): Blood diffuses in white or around yolk. It is caused by a blood clot breaking and spreading through the albumen. {c} Incubated egg: Fertile egg has a halo around the germinal disc. In advanced incubation, blood vessels or even embryo may found on the yolk. {d} Meat spots: They are fatty, fleshy or liver-like materials floating freely in the white or embedded in chalazae or attached to the yolk. Some meat spots degenerate and change in colour to reddish browning. {e} Rot and mold growth: Microbial contamination of the egg contents either by bacteria or molds produce different colours and odours depending on the kind of the contaminants.

{f} Tainted egg: Tainted eggs are those with abnormal odours. Defects that render eggs Defects that render eggs unfit for suitable for Human consumption rapid consumption Bloody egg Large air cell Incubated egg Ringed air cell Cloudy albumen Small blood spots Discoloured albumen Sided yolk Meat spots(Foreign bodies) Patchy yolk Rot and mold growth Mottled yolk Stucky yolk Dirty egg Spready yolk Tainted egg

Testing eggs for freshness (A) Egg shell:

(1) On small scale:

{a} Brine test: Eggs, under test, are transferred to a brine solution (10% Sod. chloride). Fresh eggs, with small air cell, will sink to the bottom while old eggs, with a large air cell, will float at various position and depths depending on size and site of their air cells.

Old (large air cell)

Suspected

Fresh (small air cell)

{b} Shaking test: On shaking eggs, fresh one gives no sound while old egg (aged) gives a sound as thick white becomes thin and chalazae are loosened allowing yolk to move freely within the egg.

(2) On large scale: {a} Candling:  Candling is one commercially suitable way of testing the quality of eggs without breaking their shells.  There are two types of candling: i – Individual egg candling: In which the egg is held with the broad end uppermost at a slight angle to the aperture of the candle lamp and withstands to and fro around its long axis. ii- Mass egg candling: In which eggs pass in front of the candler either in a single raw or up to 12 parallel raws in a suitable source of light. More than 150 egg can be illuminated in front of the candler at any one time.  The candling involves providing a beam of light sufficiently strong to penetrate the shell and outline the contents to detect the size of the air cell as well as the different quality defects of the egg. {b} Examination of eggs under ultraviolet-rays: (Quartz lamp) The fresh eggs (till 10 days old) when subject to U.V. rays, show a red pink shiny appearance. If the eggs are more than 10 days old., the colour will gradually change from violet to bluish. The basis of this test depends on the presence of oporphyrin in the cuticle present on the shell of fresh eggs, and as the egg becomes older and consequently having less amount of the bloom, as well as due to the effect of day light on the shell, the colour under U.V. lamp will be changed from red to bluish. This test is uncertain because the oporphyrin is present not only in cuticle but also in the shell itself. Moreover, the colour of the shell interferes with the judgment (yellowish brown or brown shells). (B) Broken-out appearance: (egg contents) The eggshell is broken and the contents are transferred to a Petri-dish to detect abnormal colour and/or smell as well as any quality defects in egg contents. {a} Fresh egg {b} Old egg: (Stale egg)  The yolk stands up well and is  No thick albumen is apparent. held centrally by the albumen.  The chalazae become unattach-  The yolk colour is an even ed and very weak. yellow.  The yolk is displaced, flattened  Both chalazae are distinct and and severely patchy or mottled. firmly attached to the yolk.  On touching, the yolk easily  There is no sign of mottling ruptures. and/ or foreign bodies.  Blood and meat spots may be  The albumen is clear with no present. tint or colour.  Differentiation between the outer thick and thin albumen is distinct.  There are no blood spots and other foreign bodies.  The germinal disc is just visible. Grading of egg quality: Egg grading involves inspection of the shell for soundness, cleanliness, apparent strength and shape, checking the interior of the egg by candling and sorting into sizes on the basis of weight. (I) Eggs are classified according to size as: Size Weight/dozen Jumbo 30 oz. Extra large 27 oz Large 24 oz Medium 21 oz Small 18 oz Peewee 15 oz

(II) Eggs are graded according to the interior quality:  The interior qualities as well as condition and appearance of the shell to Class A, Class B and Class C (clean unbroken eggs).  Class C includes all eggs, which do not satisfy the requirements of Class A and Class B but are suitable for the manufacture of foodstuffs for human use.  All eggs which do not fall into these classes are classed as (Industrial eggs) and may not be used for human consumption either in the manufacture of foodstuffs or otherwise. See the following table. (III) Dirty or broken eggs: They may not be graded

Relation to public health:  Pathogenic bacteria that can enter the egg contents either before laying or after are able to multiply rapidly as yolk is highly nutritive medium.  If such eggs are consumed raw or semi-raw may be responsible for sporadic or epidemic diseases.  Many members of Salmonellae e.g. Sal. Typhimurium etc… causing food poisoning may be found in egg contents.  Duck eggs are responsible for many cases of food poisoning outbreaks than hen eggs.  It has been found that soft , coddling or on one side did not always render an egg free from salmonellae.  Egg contents may contaminated with other food poising organisms as S. aureus, E. coli and other members of Enterobacteriacaea.  Tubercle bacilli (avian type) can be reach and infect consumers through eggs produced from diseased poultry.  To secure consumers from being infected, eggs must be obtained from clean farms applying the hygienic measures. Producing hens should be tested regularly for T.B. and Pullorum diseases. Boiling eggs for 5 minutes (hen egg) and 8 minutes (duck egg) with slow cooling destroys microorganisms may be found in egg contents.

Cleaning of eggs:

 Clean and dry eggs are essential to the production and maintenance of good quality.  Most eggs are cleaned by washing with modern egg washers designed to minimize defects may occur.  Eggs are sprayed with water rather than immersing them, using a sanitizer in water along a detergent for cleaning them, using rinse water warmer than the wash water and finally drying the eggs with hot air.  Rotating the eggs during washing and using pressure, sprays and oscillating brushes, provides scrubbing action by the washers.  The most often used chemical is any of several chlorine compounds at level of over 50 ppm active chlorine.

Preservation of eggs: Preservatives may be used on the shells of eggs, in the atmosphere around them, or on warps or containers for eggs. The chief idea of preservation is to prevent entrance of organisms inside the eggs and to prevent multiplication of the microorganisms, which may gain access inside the eggs. A large number of different substances have been applied to the surface of the shells of eggs or used as packaging material about eggs to aid in their preservation. Some of these substances are primarily to keep the shell dry and reduce penetration of oxygen into the egg and passage of

CO2 and moisture out: waxing, oiling the shells and otherwise sealing are examples. Other materials inhibit the growth of microorganisms and some are germicidal. Material used for the dry packaging of eggs in the home includes bran, salt, lime, sand, sawdust and ashes.

Methods of preservations:

(A) On small scale:

{1} Water glass: The eggs are immersed in a solution of sodium silicate, the shell becomes dull in appearance and the eggs can store for many months. The solution is inhibitory because of its alkalinity. {2} Lime-water: Composed of: 4 parts slaked lime 1 part sodium chloride 20 parts of water, Allow solution to stand for a week, decant and rinse the eggs in the resulting liquid. The shells become rough in texture and white dull in appearance. Both methods of treatment can be detected by applying a drop of phenolphthalin, pink colour appears. {3} Using oil and sawdust: The eggs are wrapped with oil and place in layers surrounded with sawdust. The preserved eggs should be stored in a cool place and should not subjected to violent agitation. (B) On large scale: {1} Cold storage (chilling): Most shell eggs are preserved by chilling. They are selected for storage on the basis of their general appearance and a result of candling. The eggs should be cooled as promptly as is practicable after production and held at a temperature and relative humidity that will depend upon the anticipated time of storage. Over seas, temperatures of 0 to 1 0C are more common, with 80 to 85 % relative humidity. Air circulation in the storage room is important, in order that the desired relative humidity will be maintained around the eggs, and a constant storage temperature is essential to avoid the condensation of moisture on the eggshells. Impregnation of the egg shell with a colourless and odourless mineral oil is a commonly employed method that keeps out moisture, shows down desiccation and air penetration, retains CO2, and retards physical and chemical changes within the egg. At present, the egg is immersed for a few seconds in a thinner mineral oil at atmospheric temperature, or preferably at about 40 0C and then drained. Oiling is used primarily for eggs to be stored commercially for long periods, after several months of cold storage atypical flavour may develop in the stored eggs. To prevent such conditions, periodical sterilization should be done with disinfectant gas as ozone (O3). It has been claimed from 0.6 ppm of ozone (in clean eggs) to 1.5 ppm (for dirty eggs) at 0 0C and 90% relative humidity will keep eggs fresh for 8 months.

{2} Oil dipping: Eggs to be oiled should be dipped in light paraffin oil (i.e. viscosity of 55 to 60), preferably at 20 0C immediately after they have been properly washed and dried. All excess oil should be allowed to drain from the eggs. Dipping the egg in water containing 4 % sodium propionate before oil dipping can prevent growth of molds.

{3} Vacuum process: The air exhausted from the cell and the shell is coated with oil. The oil is carried into the pores of the shell and acts as seals. Treated eggs have a less oily appearance. {4} Storage under carbon dioxide atmosphere:

Storage rooms are charged by CO2 in concentrations of 2.5 % at 85 % relative humidity. The effect is most potent at higher temperature of environment when refrigeration is not available. The quality of such stored egg is improved as eggs deteriorate at first due to loss of CO2. Eggs processing: (I) Heat-treating shell eggs: The process has been applied to shell eggs to inactivate the inherent enzymes, destroy the bacteria present on the shell, in the shell and shell membranes as well as in the albumen and yolk of shell eggs. Obviously, several factors must be considered such as temperature of eggs before pasteurization, size, age, grade and type of heating medium. The best results have been obtained by adjusting the eggs at room temperature (28-290C) before immersing and rotating them in oil. The temperature of oil is held at 60 0C and eggs are rotated for 10 minutes. This time-temperature factor is adjusted to prevent coagulation of egg proteins. (II) Pasteurization of liquid egg products: Eggs are pasteurized primarily to eliminate Salmonellae but in other microflora is also of considerable value. The temperature at which egg white proteins are denatured is very close to the temperature required to kill Salmonellae. For this reason, accurate temperature regulation is essential to prevent the loss of functional properties in the white. The procedure is as follows: {A} Eggs whites are acidulated with lactic acid to pH 6.8-7.3, then aluminum sulphate is added to prevent damage to egg whites, by heat. The eggs can be pasteurized at 60 0C for 3.5 minutes. {B} Egg whites are heated to 51.7 0C for 1.5 minutes to inactivate the enzyme catalase. Hydrogen peroxide is added and pasteurization process continues at 51.7 for 2 minutes. After cooling, the enzyme catalase is again added to remove

H2O2. {C} Egg whites are heated at 56.7 0C for 3.5 minutes under vacuum: Normally, less than 1% of the bacteria in raw egg product survive pasteurization. The genera may be found in the pasteurized egg products are: Alcaligenes, Bacillus, Proteus, Escherichia, Flavobactericum and Gram positive cocci. Proposed temperature for pasteurization in 3.5 minutes Product ( 0C) calculated Proposed Whole egg 60 60 Yolk plasma 61.4 61.4 + 10 % sugar 63.13 63.8 + 10 % salt 65.4 63.8 Whites: - pH 7 59.4 60 - pH 9 56.6 57.12

Egg products: (1) Liquid eggs: Eggs for processing are broken out either by hand or machine, examined for evidence of spoilage by sight or smell, then homogenized as whole egg or separated into white or yolk. Egg products must now be pasteurized prior to freezing or drying in order to destroy Salmonella. After screening to remove chalaza, shell fragments, etc… eggs are pasteurized at 60-62.8 0C for 1-4 min. prior to cooling. Cooling may be carried out in tanks provided with cooling coils and paddles, which agitate the product to facilitate cooling.

(2) Frozen eggs: After cooling to 4.4 0C, the may be placed in metal cans holding about 30 lb. of product. The filled cans are then placed in a cold room at -17.8 0C to – 20.5 0C until the product is frozen, after which the product is held at –17.8 0C or lower until shipped out to the distributor or to the point of utilization. Frozen whole egg magma and frozen yolks are subjected to deterioration during frozen storage. Ingredients in the yolk tend to form a gummy mass during frozen storage. In order to prevent this, 5-7.5% salt or glycerin or 5-10% sugar may be added and mixed with the product.

{3} Dried eggs:

Egg white, yolk or whole egg magma may be spray- dried by forcing the product through a nozzle (to form droplets) into a chamber of heated air where most of the moisture is removed from the droplets to the heated air, which is vented to the outside, and the dried product falls to the bottom of the drier from where it is collected.

Another method is the roller or drum process in which the liquid egg is passed over a heated drum, with or without vacuum. Air-drying is accomplished by means of open pans or by the belt system where the egg liquid is on a belt that passes through a heated tunnel (60 to 71.1 0C). Spray drying or pan drying, combined with tunnel drying is used for egg white. Formerly eggs were dried to a moisture content of about 5%, but it has been shown that the keeping quality of dried white or whole egg is improved as the moisture content is decreased toward 1 %, and then trend in that direction. A mixture of two enzymes glucose oxidase and catalase, may be used to remove sugars from eggs, which must be carried out prior to drying.

Microbiological Examination of eggshell, eggs contents and egg products (I) Egg shell: (A) Swab contact method: 1. A sterile swab, in peptone water, is wrapped on the surface of the eggshell. 2. The swab stands in a test tube containing sterile peptone water or broth and incubated for 24 hours at 370C. 3. The different microbiological examinations could be done. (B) Rinse solution method: 1. The egg is immersed in a beaker contains 100 ml sterile tryptic soy broth. 2. The beaker is rotated gently for 15 minutes on a mechanical rotating shaker till complete washing the eggshell. 3. The rinse solution of each egg or 5 pooled eggs, from a part, 10-folds serial dilution is prepared for:  Total bacterial count  Detection and enumeration of Coliforms.  Enterococci count  Yeast and mold count 4. The other part is centrifuged and sediment is prepared for the different microbiological examinations.

(II) The contents of egg: 1. The eggshell is sterilized by either Tr. iodine or by adding few drops of alcohol then ignited. 2. By sterile scissors cuts the eggshell is cutted out around air cell. 3. The contents are removed aseptically and homogenized using a blender. 4. Examinations can be carried out on single egg or on the bulked contents of a number of eggs. 5. Serial decimal dilutions are prepared from the homogenate to estimate total viable count, presumptive test for Coliforms, Enterococci count and yeast and mold count. 6. Also, isolation and identification of S. aureus as well as Enterobacteriacaea, especially Salmonellae, are done.

(III) Egg products:

(A) Frozen whole eggs: 1. The product is sampled while still frozen. 2. The lid and top of the tin are cleaned and swabbed with alcohol and flamed. 3. The lid is removed, with sterile suitable instrument, 2 cores are removed, one from the center of the can and one at the edge extending from the top surface to a deep level as possible with the instrument used. 4. Samples are transferred to sterile container and examined as soon as possible. 5. The frozen samples are held to soften slightly and while still very slightly frozen, sample is blended thoroughly. 6. Serial decimal dilutions to 10 –5 are prepared to detect; general viable count, presumptive test for Coliforms, DMC using Breed’s method with dilation 10 –2 and isolation as well as identification of Salmonellae.

{B} Dried egg:  The same procedure for sampling is used as in frozen eggs.

{C} Frozen, dried and flakes albumen:  The same method used for frozen egg is adopted for such products.

The Food and Agriculture Organization of the United Nation (FAO/WHO, 1975) has tabulated the various microbiological criteria imposed for dried and frozen eggs by 19 counties. A summary of these criteria is presented in the following table: Microbial numbers / gm. Dried eggs Frozen eggs Standard plate count 15,000 to 600,00 10,000 to 500,000 Coliform group 10 to 100 10 to 300 Coagulase positive NDa 0.1 to 1000 NDa 0.1 to 1000 Staphylococcus NDb 20 to NDb 20 to Salmonella NDc 25 x30 NDc 25 x 30 Yeast and moulds 20 to 100 50 a- ND 0.1 = not detectable in 0.1 g. b- ND 20= not detectable in 20 g. c- ND 25 x 30 not detectable in 30 samples of 25 g. each

In addition, the FAO has established its over criteria of these two commodities, summarized as follows: n c m M Salmonella (24 g. portions) 10 0 0 0 Salmonella for special diets 30 0 0 0 Standard plate count 5 2 5x104 106 Coliform group 5 2 10 103 In which n samples are analyzed of which c samples may exceed m, but none may exceed M. Detection of inhibitory substances in eggs: Antibiotics and sulfa drugs are now used on a large scale in poultry industry as feed additives to promote growth and prophylactic agents as well as for treatment of some infectious diseases. Preparation of egg contents: 1. Each egg is carefully washed and the contents are mixed. 2. From the mixture, 2 ml are homogenized with 20 ml of solvent (40 gm Potassium hyroxide, 0.3 gm creatine are dissolved in 100 ml distilled water) 3. The homogenate is centrifuged at 3000 rpm for 10 minutes to separate the supernatant, which is used for the detection of residues. Procedure: 1. Microbiological assay by agar diffusion method is used with Bacillus subtilis as test organism and Iso-sensitest agar as substrate medium. 2. Circular wells (well technique) of 10 mm diameter are punctured carefully in the inoculated agar, with test organism, (1 x 10 6 concentration), 0.1 ml of the egg content sample (supernatant) is transferred to the well. 3. The plates are incubated at 55  1 0C for 6 hours. 4. Any zone of inhibition is recorded as positive results.