What are the common preservation methods?

What are the common preservation methods?

What are the common preservation methods? With people's living standards getting better and better, people's requirements for ingredients are getting higher and higher, and freshness is needed to ensure the delicious food. So how to keep these ingredients fresh in life? Let's look at the common preservation methods.

What are the common preservation methods? 1 What are the common saving methods?

Basically, all foods will face a problem, such as spoilage, and the preservation process before eating is very important. All foods should be stored separately according to their specific storage conditions and characteristics.

There are many common preservation methods, but there is no difference between good and bad. Only by choosing the right preservation method can different foods achieve the purpose of preservation. As the saying goes, "Use only the right ones, not the expensive ones."

Normal temperature preservation technology

As the name implies, the methods of preserving food at room temperature, such as rice, noodles, soy sauce, vinegar, salt, candy, bottled drinks and other foods that are not easy to deteriorate, are generally preserved at room temperature. Remember to be moisture-proof, pay attention to heat insulation and avoid exposure to the sun.

Cryopreservation technology

The so-called low-temperature preservation is refrigeration preservation, specifically, it is a method of using low-temperature technology to reduce the temperature of food and keep it at a certain low temperature, thus inhibiting spoilage and enzyme activity and prolonging its storage period.

Low temperature preservation is generally used for perishable products such as meat products, cakes, yogurt and cheese. In the low temperature range, when the temperature is higher than the freezing point of food, the growth rate of microorganisms in food will slow down. Below freezing point, general microorganisms will stop growing.

Freezing preservation technology

Frozen drinks, quick-frozen rice flour products, minced fish products, raw livestock and poultry products, aquatic products, etc. It should be frozen. After the primary preparation, the tissue structure of the sample was destroyed to some extent, and some surface microorganisms were mixed into the tissue, which accelerated the change of the food sample and made it more perishable.

Compared with the sealed samples, the storage method has changed. For example, samples stored at room temperature, such as canned food and dried beancurd, should be stored in cold storage after primary preparation, otherwise they will easily deteriorate, which will directly affect the accuracy of test data.

Non-thermal sterilization and preservation technology

Non-thermal sterilization and preservation technology, as its name implies, is a kind of preservation technology that kills or destroys harmful substances and therapeutic microorganisms in fresh food by non-heating method, so that fresh food can meet the sterilization requirements and standards.

Compared with ordinary heating sterilization technology, non-thermal sterilization technology has the characteristics of faster sterilization speed and avoiding the damage or nutrient loss of fresh food caused by high temperature heating. This fresh-keeping technology is very suitable for food sensitive to heat source.

Biological preservation technology

Biological preservation technology is an advanced preservation technology. Specifically, some natural substances with bactericidal or bacteriostatic characteristics are prepared into solutions with appropriate concentration according to a certain proportion, and microorganisms in fresh food are stopped from growing or reproducing by soaking, spraying and smearing, so as to achieve the purpose of preservation. Mainly used for fruits and vegetables.

Because the raw materials used in biological preservation come from natural organisms, it has the advantages of safety, non-toxicity and degradation. With the continuous improvement of people's safety awareness, biological preservation technology is favored by people, so this food preservation technology has a good application prospect.

Vacuum preservation technology

Vacuum preservation technology is a new technology for the processing and circulation of fresh agricultural products, which mainly includes decompression storage and vacuum rapid cooling.

Vacuum cooling (vacuum cooling) is also known as vacuum precooling. Its basic principle is that part of humid air in goods is rapidly evaporated and cooled, and its characteristic is that the cooling speed is faster than that of traditional cooling technology.

For the fruit and vegetable vacuum cooler, when the pressure in the vacuum chamber drops to the saturated evaporation pressure, that is, the flash point value, the water on the surface of the product begins to boil and evaporate, and the temperature of the product decreases due to the evaporation of water. As the pressure continues to decrease, the product can be cooled to the required temperature.

Above the pressure flash point, the article will not be cooled in vacuum, but only in an environment with gas flowing. For the vacuum cooler that cools the high-temperature cooked food just out of the pot, as long as the vacuum is pumped, the temperature of the goods will drop.

Other methods

There are other methods: microwave, irradiation, drying, boiling, burying (deep water storage, cellar storage), ultrasonic, dehydration, chemical preservation (sugar pickling, salt pickling, vinegar pickling) and so on.

What are the common preservation methods? 2 What are the common preservation methods?

There are also blanching, cold storage, drug preservation and low-temperature controlled atmosphere storage, all of which need to be carried out at low temperature.

1, blanch and save

The folk method is to soak the ear in boiling water at 100℃ for a while, then lift it up and hang it in the air to dry, so that the activity of polyphenol oxidase in the fruit can be inhibited, and the fruit will not go bad and moldy within 10d, and the original flavor will be maintained. Fujian Fruit Research Institute improved this method. Blanch the ear in boiling water at 100℃ for 5 ~ 15s, then dry it with cold air, pack it in plastic bags, and store it in cold storage at 2℃.

After 22 days, the appearance color is similar to that of fresh fruit. Although the endocarp has been browned evenly, the flavor is normal, and the good fruit rate reaches 100%, which can basically achieve the purpose of preservation.

2, quick-frozen preservation

Quick freezing and cold storage is to reduce the central temperature of longan fruit to -30℃ in a short time (generally less than 1h) and store it at-18℃ for a long time. During storage, the fruits were completely frozen in microcrystals, the metabolic activities stopped, the cells were slightly damaged, and the destructive effect of microorganisms was inhibited.

The fruit can maintain its original appearance and inherent flavor, with less loss of nutrients. Choose varieties with thick skin, crisp and hard meat and high sugar content in pulp for quick freezing and cold storage; The fruit should be completely ripe, but not too ripe.

Cold chain circulation must be adopted in the transportation and sales process, and it should be brewed or soaked with ice water or cold water after thawing. After thawing, dry the water drops on the surface of the fruit with clean gauze and serve. The disadvantages of this method are large investment and high cost, and it is difficult to popularize.

3. Preservation and preservation of drugs

Fujian Agricultural University adopted sec-butylamine treatment combined with low temperature storage, and achieved remarkable results. Practice: The fruit ear is packed in a 2kg box, and the box of 16 is used as a film tent. According to the ratio of 0. 1ml sec-butylamine per kilogram of fruit, the sec-butylamine was put into the shed to fumigate the fruit, and a film shed was set in the cold storage at 2, 5 ~ 3 and 0℃. After storage for 38 days, the good fruit rate was 99.3% and the weight loss rate was 2. 18%.

The color of the fruit is basically normal, the skin is still green after scraping, and the taste of the pulp is normal. Although the texture is slightly softer than fresh fruit, it still meets the requirements of canning process.

The fruit soaking method of sec-butylamine is to dilute the stock solution of sec-butylamine into 30 times solution, soak the fruit 10min, take it out to dry, and put it into cold storage. The good fruit rate is 97% and 3%, but the meat quality, flavor and appearance are not as good as fumigation.

The fumigation of sec-butylamine in large tent combined with low-temperature storage is simple to operate, does not require large-scale equipment investment, has low cost, can be stored in large quantities, and is worthy of popularization and application in processing departments.

It is reported that SO2 fumigation is a new post-harvest treatment measure for longan exported from Thailand, aiming at controlling post-harvest diseases and maintaining fruit quality and good color. However, this method should pay attention to the residual level of SO2 in the treated fruit.

4. Low temperature controlled atmosphere storage

In this method, air is pumped, nitrogen is filled and oxygen is increased in the packaging bag or barrel of longan fruit at low temperature to achieve the purpose of preservation.

Fujian Fruit Research Institute reported that when the oxygen concentration in the packaging bag was 3% ~ 5% and the carbon dioxide concentration was 5%, the fresh-keeping effect was better, but the endocarp still showed uniform browning, indicating that hypoxia could not effectively prevent the endocarp from browning.

When the oxygen concentration is constant and the carbon dioxide concentration increases from 5% to 10%, the alcohol content in the pulp increases greatly, which obviously affects the fruit quality. The practice of Fujian Agricultural University is to select excellent fruits that are fresh, free from pests and diseases, mechanical damage and fruit cracking, disinfect them with bactericide, dry them with liquid medicine, pack them in bags or barrels, then pump air and fill them with nitrogen (generally, full pumping air and filling them with nitrogen), and then store them in the cold storage at 0 ~ 5℃.

After 40 days' storage, the good fruit rate of bagged fruit is over 90%. After storage for 90 days, the good fruit rate of barreled fruit (20kg per barrel) was over 94.5%, and the weight loss rate was less than 5%. After120 days, the good fruit rate was still 83.6%, and the weight loss rate was also below 10%.

Longan fruit is very sensitive to storage temperature, and it is most suitable to keep a stable low temperature of 0 ~ 5℃, which cannot exceed 8 ~ 10℃. Low-temperature spontaneous modified atmosphere storage has the advantages of simplicity, easy operation, good antiseptic and fresh-keeping effect, and no chemical pollution. It doesn't need complicated special equipment, has low cost and is easy to popularize.

What are the common preservation methods? 3 What are the food preservation methods in daily life?

Vacuum fresh-keeping bag

Vacuum preservation box

Quick-frozen preservation method: this kind of thing is the most common and commonly used in daily families. The advantage is that the preservation method is convenient and easy to operate, and it is mostly used for meat and fish. The disadvantage is that it will affect the taste and nutrition of food.

Chemical preservation method: This method is mostly used in food production. Adding certain chemicals can prolong the storage time of food. The advantage of this method is long storage time, but the disadvantage is that eating too much food with chemical additives is harmful to people.

Vacuum preservation method: this method is the best way to keep the original flavor of food among many preservation methods. It needs vacuum preservation machine, vacuum preservation box and other tools to isolate food in vacuum to reduce the growth of bacteria and the loss of oxidized nutrients. The disadvantage is that the storage time is short.

Fumigation and air drying: the advantage is to give food another taste. Cooking can keep food fresh for a long time. The disadvantage is that the operation is too complicated and takes a long time.