Egg Contamination (PhD 2024-2025) Lecture 1 PDF

Advance Food Contamination (PhD 2024-2025) Lecture 1 Egg Contamination By Dr. Shahrazad M.J. Al-Shadeedi Professor of Poultry Products Technology Public Health College of Veterinary Medicine University of Baghda...

Advance Food Contamination (PhD 2024-2025) Lecture 1 Egg Contamination By Dr. Shahrazad M.J. Al-Shadeedi Professor of Poultry Products Technology Public Health College of Veterinary Medicine University of Baghdad 2024 / 2025 1 Definition of the Egg Scientific The egg is the reproductive cell or organic vessel containing the zygote in which an embryo develops until it can survive on its own, at which point the animal hatches. An egg results from fertilization of an egg cell. Most arthropods, vertebrates (excluding mammals), and mollusks lay eggs. Nutrition Egg is the reproductive cell of domestic birds which belong to the Class Aves, mainly belong to the Order Galliformes and the family Phasianidea, including Chicken, Turkey, Quail, Pheasants and Partridge. Also, the family of Anatidea, including Duck, Geese and the family of Struthionidea, including Ostrich. Fowl or poultry are valuable domesticated birds reared by humans for the eggs they produce and their meat. Figure (1): Fowl or poultry species. Fowl egg belongs to the food with high nutritional quality. People eat eggs for its high nutritional value because of the optimal composition of essential amino acids and the favorable composition of fatty acids with a high percentage of polyunsaturated fatty acids and a favorable ratio of omega 6 to omega 3 fatty acids. It is economical, and quick and easy to prepare and serve. The utilization of fowl eggs for processing, also eggs pidan and balut has a long tradition in some Asian countries for centuries. 2  Figure (2): Some kind of domestic bird eggs, quail eggs (upper left), chicken egg (lower left), and ostrich egg (right). Fowl egg is one of most complex and highly differentiated reproductive cell, birds egg diverge widely in shape, volume, weight and the amount of yolk and albumen material due to genetic factors; species, breed and strain and non- genetic factors; nutrition, diseases and season. Egg structure and components An egg basically consists of three parts (Figure 3): 1. a shell 2. an egg white 3. an egg yolk An egg from a hen consists of approximately 2/3 egg white and 1/3 egg yolk. 3  Figure (3): Structure of table egg. Egg morphology and shell color Fowls egg is one of most complex and highly differentiated reproductive cell, birds egg diverge widely in shape, volume, weight and the amount of yolk and albumen material due to genetic factors; species, breed and strain and non- genetic factors; nutrition, diseases and season. The main pigments responsible for the coloration of egg of wild and domestic birds are protoporphyrin IX, biliverdin IX and biliverdin zinc chelate. Studies in more than 100 avian species provide proofs that the only pigments in blue-shelled eggs are biliverdin IX and biliverdin zinc chelate. The major pigment in eggshells of brown-egg laying hens is due to large amounts of protoporphyrin and uroporphyrin, eggshells of white-egg laying hens is due no pigments deposited on them. An Olive Egger, a chicken that lays olive green eggs, is the product of a cross between a hen and rooster that are from a brown egg and a blue egg laying breed. Eggs are laid in shades other than white have pigments deposited on them as the eggs travel through the hen's oviduct as shown in Figure (4). Researchers concluded that there is a substantial variation in the color of eggs not only within the groups, but also within the breed. 4 Figure (4): Variation in table egg shell color due to chicken breed 5 Importance of Hygienic Processing of Eggs for Food Safety Egg (Table egg) is considered among the most nutritious and healthiest foods on the planet. Egg is an excellent source of protein, with all the essential amino acids that body needs to maintain good health. In addition, it also contains several minerals and vitamins, which are required for healthy living. Eggs are accepted by all communities without restriction to any religion, and are consumed globally by children, adults, and old people. In India, the egg production in the last 25 years has increased up to 70 billion from few millions. Currently, India is the third-largest egg producer after China and USA. The leading states in egg production in India are Andhra Pradesh, Haryana, Maharashtra, Punjab, and Tamil Nadu. In India, the per capita eggs consumption has gone up from 30 to 68. It is recommended by human nutritionists that 180 eggs should be consumed per year. Egg is an important component of a healthy and balanced diet due to its nutritional richness. The consumption of egg is increasing across the globe due to better economy. Presently, the consumer is very health conscious and therefore, demands high quality of nutritious food, which is safe and wholesome and also will not produce any illness. Food safety gives assurance that the food will not cause any harm to the consumer when it is prepared and/or eaten. Food safety is as important with eggs as it is with milk and dairy products, meat and meat products, fish, shellfish and other seafood, and poultry and poultry products. There can be health risks if eggs are not handled, stored, and prepared safely. Some eggs may be contaminated with bacteria such as Salmonella, which can cause serious food poisoning in the susceptible population. Hence, it is highly imperative that egg should never be consumed in raw form. The proper heat treatment will certainly make the egg safe to the consumer. Educational programmed of the public about the health hazards due to consumption of raw foods including eggs is very much needed. The present communication delineates the importance of hygienic processing of eggs from food safety view. Spoilage of egg: Although egg is known as one of nature’s most nutritious and economical food, special care is required with handling and preparing fresh eggs and egg 6 products in order to avoid the microbial spoilage. Many bacteria and fungi can cause spoilage of various foods including eggs. A. Bacteria: Several bacteria, such as Aeromonas, Proteus, Achromobacter, Escherichia coli, Aerobacter, Micrococcus, Pseudomonas, Salmonella, Alcaligenes, Serratia, etc. are responsible for spoilage of eggs. B. Fungi: A large number of fungi belonging to the genus Aspergillus, Mucor, Cladosporium, Penicillium, Rhizopus, Fusarium, Candida, Botrytis, Thamnidium, Alternaria, etc. can result into spoilage of eggs. Penicillium species cause yellow, blue or green spots inside the shell. The pink spots is produced by Sporotrichum species. Clodosporium species give dark green or black spots. Types of rots: Several types of rots are caused by various bacteria. 1. Black rots: Bacteria, such as Aeromonas, Proteus, and Pseudomonas are responsible for black rots. 2. Pink rots: It can be caused by Pseudomonas. 2. Green rots: Pseudomonas fluroscens is the etiologic agent of green rots. 3. Custard rots: Custard rots is caused by Proteus vulgaris. 4. Red rots: Serratia can produce red rots. 5. Colorless rots: Certain bacteria, such as Acinetobacter, Alcaligens and Pseudomonas can result colorless rots. Development of off flavors: Mustiness may be caused in the eggs by bacteria, such as Achromobacter, Proteus, and Pseudomonas. Fishy flavors are produced by Escherichia coli whereas hay odor is caused by Enterobacter cloacae. The growth of streptomyces near the egg may produce the earthy or musty flavors that are absorbed by eggs. Tainting: Eggs, especially yolks, are easily tainted by strong odors, from several sources like disinfectants, soaps, diesel, petrol, paint, kerosene, varnish, citrus products, onion, garlic etc. Egg quality: The quality of eggs can be determined by following ways. A. Exterior egg quality: 1. The shell is examined for crack or unsound egg shells. 2. The shell is checked for cleanliness, strength, texture, and shape. 3. The shell should be oval with one end larger than the other. B. Interior quality: Interior quality is determined by candling to see the following: 7 1. White:-Egg white (albumen) in good quality egg should be thick, full and transparent. It should not be cloudy or discolored. 2. Yolk: Good yolk is confined within thick albumen; a small spherical shape; orange yellow color and absence of blood or meat spots. 3. Shell quality: Small thin cracks in the shell, which do not leak, are called “Checks”. Brittle thin shelled eggs are also unsuitable for transport to market. 4. Air cell: It should be of small size, shallow depth and fixed position at the broad end of the egg. Egg preservation: The principle of preservation is to create unfavorable conditions for the growth of microorganisms, which result spoilage of food. Due to spoilage, the texture, flavor and nutritive value of food are altered and thereby, rendering it inedible for human use. The preservation of food has several objectives which are mentioned as follows: 1. To prevent the spoilage of food 2. To control foodborne infections and intoxications 3. To ensure the safety of food from microbes 4. To enhance the keeping quality of food 5. To extend the shelf life of food 6. To reduce financial losses Egg is an extremely perishable product. In order to retain its freshness and quality for maximum possible duration, it should be preserved. Basic principal of preservation is to retard the microbial growth. Various techniques are employed to preserve the egg. These are summarized in brief as follows: 1. Clay pot: Eggs are paced in a clay pot buried in the ground up to its neck in a shaded area. Eggs are put in pot after collection and covered with a cloth and damp straw. Due to evaporative cooling effect, temperature of inside of pot is about 5-6 CO. Eggs can be stored for one month. This method is still used in rural areas where facilities for refrigeration and freezing are not easily available. 2. Oil coating: A thin film of oil on an egg shell fills its pores and reduces evaporation and thus spoilage of egg contents. Oiled eggs last for at least three weeks. The oil should be colorless, odorless, and less viscous. 3. Lime water: Eggs are immersed in lime water for 16-18 hours and then dried at room temperature. Eggs can be stored for 3-4 weeks at room temperature. 4. Heat treatment: Eggs are immersed for 2-3 seconds in water at 71 Co. 5. Refrigeration: For short period of storage, keep the eggs at temperature 12.5- 15.5 Co and relative humidity 70-80%. However, for long term storage, 8 maintenance of temperature at 0-10 Co with 80-90% relative humidity is necessary. Eggs can be oil treated prior to cold storage. 6. Freezing: Liquid whole egg, albumin and yolk should be stored at -32 Co or below. Food safety: Contamination of eggs poses a high risk to food safety. Therefore, following steps are necessary from egg safety point of view. 1. The staff should have knowledge and skills in food safety and hygiene. 2. Never eat raw egg. This includes runny egg whites or egg yolks. 3. Do not use the raw or soft boiled eggs in food preparation that will not be heat treated or cooked. 4. Keep the egg shall dry to prevent penetration of microbes. 5. Maintain egg quality by using good packing, storage, and transport methods. 6. Do not send broken egg, soiled egg to the market for sale. 7. Cracked egg should be eaten or sold locally for immediate consumption. 8. Dirty eggs should be properly cleaned and sold locally for consumption within a few days. 9. Eggs must be properly dried before packing. 10. It is necessary to store eggs in their original carton, and use them within 3 weeks for best quality. 11. Refrigerate leftover cooked egg dishes and use within 3 to 4 days. 12. Use hard cooked eggs within 1 week after cooking. 13. Eggs should be kept in cool temperature following packing and throughout transportation. 14. It is important to discard the eggs that are broken and leaking. 15. Use good hygiene practice (GHP) can maintain high quality and safety of eggs. 16. It is pertinent to keep egg dishes refrigerated until it is to be served. 17. Homemade foods containing raw or lightly cooked eggs are often linked to food poisoning. Hence, thorough cooking is very important to assure the safety of eggs. 18. It is advised to use pasteurized eggs or egg products. 19. For party planning, it is advised to keep hot egg dishes hot and cold egg dishes cold. 20. It is highly imperative to avoid uncooked food that contains raw eggs. 21. Do not reheat boiled eggs in the microwave. 9  22. Boiled egg, fried egg, backed egg, poached egg, boiled egg, and scrambled egg should be cooked until both the white and the yolk are firm. 23. The ideal conditions for storage of eggs are about minus 10C and between 75-80% relative humidity. There is a risk of mold spoilage when relative humidity is too high. 24. Washing of hands, utensils, equipment, and work surfaces with hot, soapy water before and after they come in contact with raw eggs and raw egg containing foods is highly imperative. 25. Egg can become contaminated from various sources, such as hands, kitchen equipments, pets, other foods, etc. 26. Hence, it is important to maintain sanitary conditions. 27. It is important to mention that a single bacterium of Salmonella in egg can multiply into more than a million in 6 hours. Therefore, consumption of contaminated egg can cause salmonellosis in humans. 28. Human carriers play a big role in transmitting some types of salmonellas. 29. As Salmonella can easily spread from one food to another one, therefore, periodical medical checkup of food handlers is mandatory. 30. Outbreaks of salmonellosis involving eggs or egg containing foods result due to inadequate refrigeration, improper handling, and insufficient cooking. Processing technology: :24 Hence, it is imperative to maintain high quality and safety by using good hygiene, cooking, refrigeration, and handling practices. It is emphasized that the children, elderly, pregnant women, and immune compromised individuals should never eat raw eggs due to risk of Salmonella that can cause life threatening infection. Emphasis is given on the use of properly cooked eggs for food safety. 11