Many office workers buy a lot of food and stuff it in the fridge for a week or more.

　　But it's not just the ingredients in the fridge that are safe, it's the wrong method, and it can also cause food to spoil. So, what should be put in the freezer and freezer respectively? How to preserve food properly? Fan zhihong, associate professor and doctor of food science, department of nutrition and food safety, college of food science, China agricultural university, is invited to explain how to use the refrigerator correctly.

　　Understand the habits of fruits and vegetables classification storage

　　According to fan zhihong, experiments showed that vegetables kept indoors at 29℃ for a whole day had less than 50 percent vitamin and more than twice as much nitrite. So most leafy vegetables are good for refrigerator storage. But cucumber, green pepper and so on but easy because of low temperature deterioration, so not suitable for refrigeration.

　　Sweet potato, taro and other low temperature tolerance ability is limited, suitable for 10℃ or so temperature storage, the refrigerator for a short time storage problem is not big, a long time will be affected by freezing, black become rotten. And the potato that belongs to tuber kind must put freezer to store however, because potato is in high temperature, easy germinate, produce a kind of toxin that calls solanine or nightshade alkali.

　　Eating a small amount will stimulate the digestive tract, causing diarrhea and other symptoms, excessive can lead to life risk, and although sweet potato, taro will germinate, but will not produce toxins, but germinate consumption of nutrients, resulting in poor taste and nutrition.

　　Most northern fruit cool storage can delay the aging process of plant tissue, suitable for refrigerator storage, but some tropical fruit low temperature easy frostbite, mango, banana, sugarcane, durian and other tropical fruits, suitable for preservation in 12℃ or so, refrigerator low temperature will make them suffer cold damage, advance deterioration.

　　Dairy products, soy products to be opened in time to eat

　　Yogurt and active lactic acid bacteria drinks need to be put in the refrigerator to keep cool, because lactic acid bacteria and other beneficial bacteria stop proliferation in the cold condition, storage at high room temperature, lactic acid bacteria are overactive to produce too much acid, but the lactic acid bacteria will die in large Numbers, lose part of the health value, and easy to make the taste too sour. Pasteurized milk (pasteurized milk) stored at room temperature can lead to rapid excess of bacteria, even if refrigerated, drink within a few hours after opening.

　　Dairy products stored at room temperature, once opened packaging, bacteria and oxygen have access to the path, easy to spoil. So open dairy products must be put in the refrigerator, and drink as soon as possible.

　　As for boxed bean curd, before sealing box, although went through antiseptic, but cannot kill bacteria completely, so bacteria still can be in freezer, multiply gradually. And tofu itself does not contain bacteriostatic components, tofu protein, more suitable for bacterial growth. Therefore, tofu should be bought as far as possible to eat less inventory, not timely before the expiration of edible can be put into the freezer temporarily frozen tofu edible.

　　Condiments should be refrigerated for long-term storage

　　Although condiments can be temporarily stored at room temperature, they can slowly oxidize fat, leading to flavor changes. If you can't finish it in two weeks, keep it in the fridge. Salad dressing, tomato sauce and oyster sauce must be put in the refrigerator after opening.

　　These foods do not need refrigeration

　　1. Biscuits, candies, pickles, sauces, dried fruits, etc., do not need to be put in the refrigerator because of the extremely low water content or the high concentration of sugar and salt.

　　2. Put tea, milk powder, coffee and other dry products into the refrigerator. If the seal is not tight, the taste and moisture in the refrigerator will enter the food, affecting the flavor and causing mildew.

　　3. Starch food such as steamed bread, flower roll and bread can be put in the refrigerator to speed up the drying and hardening of these food. If you don't eat it recently, wrap it up and put it in the freezer. Defrost in microwave for 1-2 minutes to restore the fresh and soft taste.

　　4. Putting honey in the refrigerator will cause it to crystallize out glucose. This change does not affect the safety of honey or its nutritional value, but the evenness of the taste. If chocolate is put in freezer for a long time, produce the crystal shape change of adipose crystallization easily, although won't go bad, but chocolate surface can produce hoar frost, taste is coarse, exquisite and even no longer. Therefore, honey, chocolate more suitable for room temperature preservation.

　　Frozen food should last no longer than three months

　　If household refrigerator can quickly freeze to 18 degrees Celsius, and the temperature of the disturbance is very little, so the change of frozen food for three months is not big, but a lot of family refrigerator, things too solidly furnished, in the case of overloading the refrigerator to reach a specific temperature, and household refrigerator switch, often lead to temperature changes, often affect the food shelf life.

　　Therefore, the freezing time is too long except that the taste is not fresh. During the freezing process, the vitamin will continue to deteriorate. In the meantime, the oxidation reaction of food already bears low moisture and bear low temperature, when refrigerating, continue to produce oxidation reaction, make taste, color produces change, these oxidation product enter human body, can promote human body ageing only.

　　Frozen meat can be cut up in advance

　　Meat can be cut into different shapes according to your needs before freezing. For example, meat can be cut into pieces for stews, stir-fries, shredded meat, and minced into minced meat. Wrap in plastic wrap and store separately. When it is preserved, it can be arranged into sheets. By increasing the area of contact with freezing, it can be frozen as soon as possible. The faster the freezing speed is, the faster the thawing speed is accordingly. Appropriate amount can be taken when eating, to avoid repeated thawing, resulting in a large number of loss of vitamins in meat, flavor components change, affect the taste of meat, food quality and preservation period.

　　Because the meat is very broken, so the risk of bacteria on the surface will be much greater than the large meat, and the meat in the process of cutting, knives, cutting board are breeding bacteria, so that it is much shorter than the large meat shelf life, even frozen also need to eat as soon as possible.

　　Clean up the frozen fish

　　In the case of not knowing whether the living water of the fish is safe, it is recommended to remove all the gills, viscera, scales and black film inside the belly of the fish before preservation, to prevent pollution from transferring inward in the process of storage, and then rinse with clean water a little, and then put in the quick-frozen lattice, which is more conducive to extending the shelf life of the fish. Although it has been said that scales are rich in collagen and calcium, so it is not necessary to remove them. However, heavy metals in scales are also relatively high, which is still discarded from the perspective of safety.

　　Season vegetables and fruits blanch frozen lock nutrition

　　Toona, shepherd's purse and so on are seasonal product, when can be on the market in great quantities, quick-frozen a few, retain more delicious. Wash vegetables before freezing, blanch them with boiling water, blanch them for as short a time as possible to reduce the loss of nutrients, blanch them out to dry some water, then put them in the crisper bag, and put them in the freezer until the temperature drops to 3-5 ℃, then put them in the freezer (the freezer is usually in the super thin and flat drawer above the freezer).

　　Cells of quick frozen vegetables, moisture will form a uniform, very tiny ice crystals, but too slow if frozen, minus 1 ℃ to 5 ℃ below zero in the interval to save time is too long, it will form a huge ice crystals, edible thaw, quick-frozen can ensure the integrity of the cell membrane, preserve the nutrition, on the other hand, the cell membrane rupture nutrients.

　　In the home homemade dumplings, wonton and so on, also want to use frozen way, so as to ensure that the nutrition of food does not lose. The frozen food is sealed and stored in the freezer for 1-2 months.