What are the conditions for food preservation? 1

1. Cryopreservation

Cryopreservation can inhibit the reproduction of organisms and slow down the spoilage of food, but it cannot completely kill microorganisms.

Pay attention to the control of temperature when storing at low temperature. Generally speaking, the lower the temperature, the longer the storage time.

2. High temperature sterilization

After high temperature treatment, most bacteria and enzymes can be killed. If the food is treated by sealing, vacuum and rapid cooling, it can effectively delay the spoilage of food and prolong the storage time. For example, we often drink bagged pure milk, beer, pasteurized milk and so on.

3. Dehydration and drying

Dehydration and drying is to reduce the moisture in food below a certain limit, so that microorganisms are not easy to grow and reproduce, and the activity of enzymes will be inhibited. The common dehydration methods in the family are sun exposure, shade drying, heating evaporation or freeze drying, and so on. It is worth reminding that although the method of sun exposure is the simplest, it also loses the most vitamins.

4. Improving osmotic pressure

The name seems difficult to understand, but in fact, most people have used this method.

for example, pickle food with salt or sugar. When the concentration of salt is 8%-11%, it can inhibit the reproduction of most microorganisms, but it cannot be completely killed.

To kill microorganisms, the concentration of salt should be controlled at 15%-21%; The sugar concentration of sugar-stained food should be controlled at 61%-65% to inhibit the proliferation of microorganisms.

attention should be paid to sealing and moisture-proof when storing. Common candied foods include preserved fruits, candied fruits and jam, and so on.

5. Increasing the concentration of hydrogen ions

Most bacteria can't grow and reproduce normally in the environment with pH below 4 and 5, so we can use the method of increasing the concentration of hydrogen ions to prevent corrosion. Vinegar pickling is adding vinegar to food, which is often used in fruits and vegetables, such as pickled cucumber, pickled cabbage, sour bamboo shoots and so on.

What are the conditions for food preservation? 2

1. Low-temperature storage: Low-temperature storage is a common method for storing cooked food.

its main principle is to effectively inhibit the growth and reproduction of microorganisms, reduce the activity of enzymes, weaken the chemical reaction in food, and better maintain the original flavor and nutritional value of food.

2. High-temperature storage method: High-temperature storage method is often used in food storage in catering industry, because microorganisms have weak tolerance to high temperature, and can effectively kill microorganisms when the temperature increases. And destroy the activity of the enzyme. It can prevent the influence of microorganisms on food and achieve the purpose of storing food.

The method is to first boil or steam the food thoroughly (reaching a high temperature above 111 degrees), and then take it out or soak it in the original soup. Keep it in a cool and ventilated place without stirring to prevent food from being contaminated again. This method can keep food from spoiling for a long time.

This method is suitable for preserving the finished and semi-finished products of animal foods and dried foods such as water.

3. Ventilation storage method: Ventilation storage method is mainly suitable for storing grain, dry food and food that needs air drying.

they are all afraid of mildew and covering. For example, rice, noodles, peanuts, vegetables and other foods need ventilation when stored. This can make mold difficult to grow, keep the original ingredients of food and reduce mildew.

4. vacuum sealing preservation method: the vacuum sealing preservation method is to keep food in a vacuum state without contact with microorganisms in the air. A method of sealing and preserving food, such as canned products and vacuum-packed products. This method is suitable for the preservation of various foods.

what are the conditions for food preservation? 3

1. Refrigerator storage

Proper use: First, control the temperature to distinguish whether food is suitable for storage in the cold room or the freezing room.

In addition, package different foods separately to avoid cross-infection of bacteria in food. If you want to clean the refrigerator, don't put the melted food back in the refrigerator.

health reminder: don't put food, whether raw or cooked, vegetables or meat, in the refrigerator.

Otherwise, it will not only lead to "odor" in the refrigerator, but also breed bacteria, destroy the nutrition and delicacy of food, and even lead to acute enteritis and even dysentery.

Fresh fruits and vegetables, except juicy ones such as cucumbers and grapes, should be wrapped with plastic wrap before being put in the refrigerator.

there should be a gap between the food and the refrigerator wall to facilitate air circulation; The storage time of frozen fish should not exceed 2 months, and the meat category should exceed half a year; The cold room should be cleaned and disinfected regularly, especially in summer, and it is best to clean it once a week. Only in this way can the food stored in the refrigerator be healthy and safe.

second, the selection of plastic wrap

correct use: plastic wrap should be selected according to different uses. At present, there are three main types of plastic wrap on the market: the first type is polyethylene, which is mainly used for packaging ordinary fruits and vegetables; The second category is polyvinylidene chloride, which is mainly used for packaging some cooked food, ham and other products; The third category is PVC, which can also be used for food packaging such as biscuits.

when using plastic wrap, you should carefully read the packaging label. No matter what kind of plastic wrap is made of, it should be used in accordance with the temperature range specified on the package, and at the same time, try not to let the plastic wrap come into direct contact with foods with high fat content, so as not to react and produce harmful substances that are unhealthy.

health reminder: PVC (polyvinyl chloride) material itself is safe as a food packaging material, but it should be noted that it must not be directly put into the microwave oven to heat food.

because a large amount of plasticizer needs to be added in the production process of PVC film, and the plasticizer is easily released and infiltrated into food under heating environment, which will interfere with the secretion in the body and induce diseases after eating.

in addition, do not cover the hot dishes that have just been cooked with plastic wrap. Because when the food is still hot, cover it with plastic wrap immediately, not only can't keep the vitamin C in vegetables, but it will increase its loss.

the preservation rate of vitamin c in cabbage without film covering was 85%, while that in cabbage with film covering was 71%. 97% of cauliflower is not covered with film, and only 58% is covered with film. Others, such as vegetables, have similar results. From this, it can be considered that, therefore, it is necessary to cover the fresh-keeping film after the vegetables are completely cooled, so as to protect vitamin C.

3. Preservation of the fresh-keeping box

Proper use: Do not open the fresh-keeping box immediately after taking it out of the freezer, but leave it at room temperature for 1~2 minutes before opening it.

when used in a microwave oven, if the food contains more oil and sugar, the crisper will be deformed when the temperature rises rapidly.

Therefore, it is best to use a special box for microwave oven to heat the above food. The bubbles of carbonated drinks (soda, cola, etc.) will make the sealing ability of the fresh-keeping box lose, and hot food will also make the sealing performance of the fresh-keeping box decline. Please try to avoid storing such food in the fresh-keeping box. The storage time of food is different, so don't rely solely on the sealing ability of the fresh-keeping box, and eat it as soon as possible.

health reminder: before using the fresh-keeping box, be sure to confirm what kind of raw materials it belongs to. Fresh-keeping boxes made of non-food plastics should never be used, otherwise it will do harm to human body and have potential hazards of carcinogenesis and teratogenesis. From the appearance, the quality fresh-keeping box is exquisite and fine, and it smells no irritating odor.