What are the common food preservation methods?

The principle of food preservation is to use a series of biochemical functions such as high salt permeability, microbial fermentation and protein decomposition to inhibit the activities of harmful microorganisms and increase the color and flavor of products. Its changing process is complex and slow.

2. Smoked storage

In the process of smoking, various aliphatic and aromatic compounds such as alcohol, aldehyde, ketone, phenol and acid in smoked products are condensed and deposited on the surface of the products, and penetrate into the inner layer near the surface, thus making the smoked products have unique color, fragrance and certain preservation.

Phenols and aldehydes in cigarettes are the main components of the unique flavor of smoked products. Phenols infiltrated into subcutaneous fat can prevent fat oxidation. Phenols, aldehydes and acids can also inhibit the growth of microorganisms. Bacteria that do not produce spores are smoked for 3 hours, and pathogenic bacteria such as typhoid fever and staphylococcus are smoked.

3. Quick freezing and drying

This is a dehydration process, and food does not need to be preserved or refrigerated. When food absorbs water, it will return to its original state and taste. This method can be used to preserve various foods.

Freeze food in the refrigerator, take out the air in the refrigerator and the ice will evaporate. This process is called quick freezing and drying. The process is to dry frozen food by moisture sublimation under low pressure, and sublimation is the process of turning ice bricks into water vapor without liquid state.

The food treated by quick-freezing and drying method has little weight loss, but the weight becomes very light. After adding water, the food gives off a natural taste.

Quick-frozen drying method has many advantages: it can keep food dry and can be preserved for a long time; The storage area of pickled food is smaller than that of other methods, and the storage area of dried food is only 10% of that of fresh food.

Dry grain is easy to transport and store, and the cost of drying and storage is lower than other preservation methods. In addition, there is no loss after buying dry goods, and the weight and cost are easy to control.

Step 4 refrigerate

Refrigeration of fresh food can only inhibit food decay, but it can't ultimately prevent food decay. The purpose of cold storage is to slow down the rate of food decay.

In the temperature range of-1-8 degrees, the lower the temperature of the cold storage room, the slower the growth of microorganisms and the slower the biochemical reaction that deteriorates the taste, color, tissue and nutritional components of food. It is very important that food should not be contaminated by knives before refrigeration. Lowering the temperature of food in this temperature range can reduce the risk of poisoning.

5. Quick freezing

Quick freezing is to put food in a shallow box, put it on a hollow shelf, and freeze it for 60-90 minutes according to the size of the food through low-temperature refrigeration and extrusion, so as to achieve the purpose of freezing the food.

Equipment used, such as flat freezer, airflow freezer, cryogenic liquid immersion freezer, still air cooling room, spray freezer and freezing flow. Spray freezing device, also known as cryogenic freezing, is a method of freezing food at extremely low temperature by using liquid nitrogen or carbon dioxide, which is faster than any other method.

The food to be frozen is put on the conveyor belt and sent to the thermal insulation freezing tunnel. Liquid nitrogen or carbon dioxide is injected into the tunnel through a sprayer and gasified, resulting in an extraordinary freezing process. Freezing flow is a method that can be used to freeze food.

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