Hygiene and management of eggs and egg products
作者：admin 点击次数：112 发布时间：2025-06-02
1. Eggs and egg products and microbial contamination
Eggs generally refer to eggs produced by avian animals, including eggs, duck eggs, goose and pigeon eggs, and crane eggs. Egg products are made of a variety of fresh poultry eggs as raw materials, processed products, including reconstituted eggs, ice egg products and dehydrated egg products, among them, the largest amount of people's daily consumption and food industry production is eggs and their products, followed by duck eggs. Under normal circumstances, the ovaries of poultry are sterile, and the oviducts of poultry also have a self-defense mechanism to prevent and eliminate microbial contamination, so there are usually no microorganisms present in newly laid fresh eggs. There is a layer of mucus gum layer on the surface of the eggshell of the newly laid egg, which has the effect of preventing water evaporation and preventing the invasion of external microorganisms. Microorganisms play a major role in the spoilage of eggs. Poultry eggs are rich in organic matter, inorganic matter and vitamins, when microorganisms invade the egg, under the appropriate environmental conditions to grow and reproduce rapidly, the complex organic matter in the egg is decomposed into simple organic matter and inorganic matter, in the process, the egg spoilage. The growth and reproduction of microorganisms are closely related to environmental factors (such as temperature, degree, etc.). If the growth and breeding environment is suitable, the eggs are easy to spoil, on the contrary, the eggs are not easy to spoil, which is conducive to preservation.
2. Ways of microbial contamination of eggs and egg products
(1) The source of microorganisms in eggs and egg products
1. Although the reproductive organs of the female poultry are directly adjacent to the cloaca during the egg formation process, there are no microorganisms under normal circumstances, and it has a certain defense function. However, sick chickens and eggs may be contaminated with microorganisms during the formation process. First of all, because the sick chicken is weak and has poor resistance, if the feed is contaminated with Salmonella, the Salmonella can enter the human blood through the digestive tract of the chicken, and finally transfer to the ovaries to invade the human egg, which makes the egg contents contaminate Salmonella. Secondly, the ovaries and fallopian tubes of sick chickens often have pathogenic bacteria that invade people, and the eggs may be contaminated with various pathogenic bacteria. For example, when a hen suffers from diarrhoea, Salmonella dysentery can be present in the ovaries, and the eggs laid by the chicken can then be infected with Salmonella diarrhoea.
2. Contamination during egg storage
Poultry eggs have a certain defense ability against microbial invasion on eggshells, and the outer eggshell membrane, inner eggshell membrane and protein membrane all have this function. The lysozyme in the protein can kill various microorganisms in the egg liquid, but these functions gradually decline with the extension of storage time, and the microorganisms slowly become easy to invade humans and reproduce. Fresh eggs have a different length of storage period in the field of human circulation, in this process, due to various environmental influences, external microorganisms contact the eggshell through pores or cracks to invade the egg, causing changes in the contents. The microorganisms commonly found in eggs are mainly bacteria and molds, and most of them are aerophilic bacteria, but there are also aerogenous bacteria. The bacteria found in eggs mainly include staphylococcus, streptococcus, Escherichia coli, Proteus, Pseudomonas, Salmonella, etc.
(2) The types of eggs that have spoiled
The spoilage of poultry eggs can be roughly divided into two categories: bacterial spoilage and mold spoilage, 1. Bacterial spoilage
Bacterial spoilage refers to spoilage caused by microorganisms dominated by bacteria. The spoilage of eggs is also very complex due to the different types of bacteria.
After the bacteria invade the egg, the general egg white first begins to deteriorate, and then the yolk is harmed. At the beginning of the albumen spoilage, a small part is pale grayish-green, and then this color expands to the whole albumen, and the albumen becomes thin and has a putrefactive odor. The yolk floats, adheres to the shell and gradually dries out, and the yolk loses its elasticity and breaks to form a loose yolk. The liquid of this egg is cloudy and the process of decay is very rapid, producing a large amount of hydrogen sulfide and quickly turning black, simply known as black rotting eggs. These eggs are gray in color and have a stench escaping from the egg pores. Due to the accumulation of gases, the shell of the egg may be forced to break by the internal gas, and the contents flow out to emit a strong odor, and the black rot egg is the highest stage of egg rot. 2. Mold spoilage
Fungal spoilage refers to the spoilage caused by microorganisms dominated by mold, and brown or other colored filaments often appear in eggs, mainly due to brown mold. Others, such as Penicillium, Aspergillus and White Mold, can cause different degrees of spoilage of poultry eggs.
Mold growing on eggshells is usually visible to the naked eye, and the mycelium of molds that invade people through the eggshell stomata first grows on the inner eggshell, and the mold near the air chamber multiplies the fastest because the air chamber contains enough gas for them. Then it destroys the inner eggshell membrane and protein membrane, enters the protein, and continues to develop and reproduce, and the part of the bacteria reproduction forms a very small colony, which is sometimes in the shape of a small class point with a light color, and sometimes the whole eggshell is filled with tiny small spots, which is the initial metamorphic stage. As the mold colonies continue to multiply and the confluence of similar colonies, the mold expands, making the egg a "spotted egg", and the egg deteriorates further. Finally, due to the continuous development of mold and the collection of mildew, the whole inside of the egg is covered with dense mold, this kind of egg has been opaque when viewed under the light, and the inside is black, becoming a "mold rotten egg", at this time the spoilage of the egg has developed to a serious extent, and the spoiled egg infested by mold has a special moldy smell and rancid smell. A spoiled egg is rarely caused by the invasion of one microorganism, but by a combination of microorganisms that cause spoilage.
3. Measures to prevent microbial contamination of eggs and egg products
(1) Keep the environment clean
If the hen lays eggs and stores fresh eggs in a clean place, the chance of microbial contamination of fresh eggs is reduced, which is conducive to the preservation of eggs.
2) Suitable temperature depression is an extremely important environmental factor affecting the spoilage of poultry eggs, and fresh eggs are prone to spoilage at higher temperatures. Because most of the bacteria inside and outside the eggshell belong to mesophiles, the temperature required for their growth is 10-45 °C (the optimal temperature is 20~40 °C). Therefore, the higher temperature is the suitability for the growth and reproduction of the south, so that the microorganisms outside the eggshell are easy to enter the egg, and the microorganisms in the egg develop and reproduce rapidly, decompose the nutrients in the egg liquid, and cause the rapid chemical and biochemical changes of the egg. Therefore, in the hot summer, the most likely to appear rotten eggs, the high temperature accelerates the evaporation of the water in the egg from the eggshell pores to the outside, increases the protein moisture to the egg yolk, makes the egg yolk membrane overly tense and loses its elasticity, and disintegrates into a loose yolk egg. The high temperature strengthens the activity of enzymes in the egg, accelerates the decomposition of nutrients in the egg, and promotes the spoilage of the egg.
(3) Appropriate humidity
Eggs are susceptible to spoilage in a high humidity environment, because the growth and reproduction of microorganisms requires a certain amount of humidity in addition to the right temperature. For example, under suitable temperature and humidity conditions, E. coli can reproduce hundreds of millions of offspring after 24 hours after 24 hours of reproduction every 20 minutes. If there is only the right temperature and no suitable humidity, the growth and reproduction of microorganisms will stop, or even die. Therefore, in the temperature and humidity environment suitable for microbial activities, the microorganisms on the eggshell are active and the fecundity is enhanced, which is bound to easily invade the human egg, and multiply in large quantities in the egg, so that the egg quickly spoils.
The growth and reproduction of mold is most closely related to humidity, as long as the humidity is right, it can grow and multiply even at low temperatures or even below zero. Mold that is growing on the eggshell can also invade the egg. Therefore, in an environment with high humidity, it is most likely that the eggs will spoil with mold.
(4) Protective shell outer membraneThe function of the outer membrane of the shell is mainly to protect poultry eggs from microbial invasion, so the outer shell membrane is the first line of defense for poultry eggs to prevent microbial invasion. The outer membrane of the shell is easy to disappear or fall off, and after the outer membrane of the shell disappears or falls off, the external bacteria, bacteria and other microorganisms will invade the egg through the pores, accelerating the decay and deterioration of the egg.
(5) Do not make the egg bright and damaged
The eggshell has the protective effect of protecting the egg liquid from the invasion of microorganisms, if the eggshell is damaged, then the microorganisms are more likely to invade the human egg liquid, accelerating the spoilage of the egg.
(f) Use fresh eggs
Fresh eggs contain little microbial contamination or even sterility; Stale and spoiled eggs are highly contaminated by microorganisms and are highly susceptible to spoilage.