Control of the most popular food spoilage

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Control of food spoilage

③ thawing

thawing is the reverse process of freezing. Usually, the surface of the frozen product is heated and thawed first, and a certain temperature gradient is maintained with the center of the frozen product. For various reasons, the thawed food may not be able to return to the state before freezing

when the frozen food is thawed, the ice crystal heats up and dissolves, the food material softens due to the ice crystal dissolution, and the microorganisms and enzymes begin to be active. Therefore, the thawing process should be designed to avoid possible losses due to thawing. Different thawing methods should be adopted for different foods

usually thaw in the flowing cold air, water, salt water, water ice mixture, etc. as the thawing media. It is better to control the temperature at 0 ℃ ~ 10 ℃, which can prevent the food from causing the activities of microorganisms and enzymes under excessive temperature and prevent the evaporation of water. For the thawing of ready to eat food, high temperature can be used for rapid heating. Microwave thawing is a good method for thawing. The energy occurs both inside and outside the frozen product. The thawing time is short and the exudate is small, which can maintain the good quality of the thawed product

when the meat in good frozen state is thawed slowly, the dissolved water is absorbed by the meat again, with less dripping liquid, and the meat quality can basically return to the original state. For the meat with poor freezing state, more dripping liquid is produced during thawing, and the weight of the meat is lost more. Some soluble substances in the meat are also lost, and the quality of the meat is reduced

⑶ CA controlled atmosphere storage (CA controlled atmosphere storage)

CA controlled atmosphere storage refers to the use of gas barrier materials to seal food in a gas changed environment, so as to inhibit the growth, reproduction and biochemical activity of spoilage microorganisms, and achieve the purpose of extending the shelf life of food

① principle of controlled atmosphere preservation

the deterioration of fruits and vegetables is mainly due to the respiration and evaporation of fruits and vegetables, microbial growth, oxidation or browning of food ingredients, which are closely related to the environmental gases of food storage, such as oxygen, carbon dioxide, nitrogen, moisture and temperature. If the composition of environmental gas for food storage can be controlled, such as increasing the proportion of CO2 and N2 in the environmental gas, reducing the proportion of O2, and controlling the factors of food deterioration, the purpose of extending the fresh-keeping or preservation period of food can be achieved

CA preservation can reduce the respiratory intensity of fruits and vegetables; Reduce the sensitivity of fruits and vegetables to ethylene; Prolong the life of chlorophyll; Slow down the change of pectin; Reduce the accumulation of acetaldehyde, alcohol and other toxic substances in fruit and vegetable tissues under chilling injury temperature, so as to reduce chilling injury; Inhibit the activities of food microorganisms; Pest prevention; Inhibit or delay other adverse changes. Therefore, modified atmosphere preservation is especially suitable for fresh meat, fruits and vegetables, and can also be used for the preservation or preservation of grains, eggs, meat, fish products, etc

generally speaking, it is expected to reduce the oxygen partial pressure in the gas components as much as possible during the storage of fruits and vegetables. However, if the oxygen concentration drops too low, the organic matter in the body cannot form aerobic decomposition, which will cause anaerobic fermentation harmful to the quality. Therefore, when reducing the concentration of oxygen, it should not cause anaerobic respiratory disorder. Increasing the concentration of carbon dioxide in the environment can reduce the speed of fruit and vegetable ripening reaction (Synthesis of protein and pigment), inhibit the activities of microorganisms and some enzymes (such as succinate dease and cytochrome oxidase), inhibit the decomposition of chlorophyll, and change the proportion of various sugars, so as to maintain the quality of fresh vegetables and fruits. However, if the concentration of carbon dioxide is too high, it will cause physiological obstacles to normal respiration, and shorten the storage time instead. The optimum carbon dioxide concentration of all kinds of vegetables and fruits are different, generally 2%-3% for fruits, and 2.5% ~ 5.5% for vegetables developed by impact testing machine of vegetable Jinan testing machine factory. At the same time, they are also affected by oxygen concentration and ambient temperature. Too low oxygen concentration or too high carbon dioxide concentration may cause abnormal metabolism of fruits and vegetables, thus causing tissue damage. The table lists the process conditions of modified atmosphere storage of various vegetables and fruits for the lamp materials of the new generation 1 models that BMW is studying

② methods of controlled atmosphere storage

according to the principle of gas regulation, controlled atmosphere storage can be divided into MA (modified atmosphere) and Ca (controlled atmosphere). The former refers to the establishment of modified atmosphere control system with improved gas, which will not be adjusted in the future storage period; The latter means that during storage, the gas concentration is always controlled within the 4-week value or range under a constant look 1. This method has a more accurate effect. In order to control the gas environment of food storage, the food must be enclosed in a certain container or package. Such as controlled atmosphere warehouse, controlled atmosphere truck, controlled atmosphere stack, controlled atmosphere bag (cap, or map), coating preservation, vacuum packaging and inflatable packaging

table various vegetables The technological conditions of fruit controlled atmosphere storage

product name gas composition temperature ℃ product name gas composition temperature ℃

oxygen% carbon dioxide% oxygen% carbon dioxide%

Apple 32 ~ 80 ~ 8 orange is the best closed experimental machine 3 ~ 52 ~ 46.5

onion 2 ~ 30 ~ 212 ~ 14 tomato 3 ~ 105 ~ 109.0

banana 5 ~ 105 ~ 100 Cucumber 3 ~ 165 13

strawberry 3 ~ 55 ~ 100 lettuce 3 ~ 52 ~ 30 ~.A 1

peaches 24 ~ 50 mushrooms 3 ~ 53 ~ 100 ~ 1

grapes 0.5 ~ 11 ~ 212 ~ 14 cauliflower 15.0 ~ 1

lemons 5 ~ 105 ~ 104 ~ 6 pears 4 ~ 53 ~ 40

there are many methods of air conditioning, mainly including natural air conditioning, replacement air conditioning (i.e. replacement packaging of nitrogen and carbon dioxide), oxygen absorbent packaging, coating air conditioning, decompression (vacuum) preservation and inflatable packaging. But in general, the principle is based on reducing the oxygen content, increasing the concentration of carbon dioxide or nitrogen, and keeping the gas composition in the desired state according to the different requirements of each storage

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