Preservation and preservation of vegetables

Preservation, Preservation, and Preservation Techniques for Vegetable Storage Abstract Vegetable preservation and preservation technology can be divided into two types, fresh preservation and long-term storage preservation and preservation. Fresh vegetable circulation technology Fresh vegetables continue to breathe during the circulation process, and during the summer high temperature period, they easily lose water and rot, which often has serious impact on quality and quantity. According to reports in France, the direct transportation of vegetables can be as high as 10-25%, and after precooling, the loss can be reduced to 1-3%. After harvested vegetables, such as directly sent to the cold storage, the preservation time is only about 10 days. Pre-cooling and then enter the cold storage, its preservation time can be extended to about 20 days. Japanese scholars have studied that the rotting rate of vegetables caused by warming is 3 times that of 0°C at 5°C, 4 to 5 times at 10°C, and 8 to 10 times at 20°C. It can be seen that pre-cooling vegetables can not only reduce losses, but also extend preservation time and reduce storage costs. It is an indispensable and important part of transport and storage. The main circulation fresh-keeping measures used abroad are pre-cooling technologies. The methods are as follows. 1. Air pre-cooling is currently the most commonly used method. It uses a freezer to cool the air, so that cold air can be brought into contact with vegetables and pre-cooled. The heat transfer rate between vegetables and cold air is proportional to the cold air flow velocity (wind speed). The higher the wind speed on the vegetable surface, the colder the air and the faster the cooling rate. Pre-cooling is based on the principle of rapid cooling. In order to improve the cooling rate, various methods can be applied, such as differential pressure ventilation pre-cooling, pre-cooling blowing air cooling, and tunnel pre-cooling. Differential pressure ventilation pre-cooling is a pre-cooling method that is currently considered very promising in foreign countries. During the pre-cooling, the cold air ventilation ducts are installed on the top of the pre-cooling warehouse, and high-pressure cold air is introduced. At the other end of the cold storage room, exhaust fans are arranged with exhaust fans or exhaust fans. A gas pressure difference is generated between the precooling room and the precooled vegetables. Since the gas flows from the high pressure to the low pressure direction, the moisture in the vegetables evaporates and the temperature drops rapidly, so that the precooling effect is achieved. Air pre-cooling is applicable to all kinds of vegetables and various packaging methods. The effect is good and the operation is simple. The disadvantage is that the cold shortage is slow and the impact is timely listed. 2, cold water pre-cooling is a method of using water as a medium to transfer the heat of the vegetable surface. Cold water cooled by a refrigerator is usually used to pre-cool the vegetables. Specific methods include water immersion, water spray, and spray. The method has a short cooling time and good effect. The disadvantage is that vegetables are difficult to dry after soaking in water and are prone to mildew and spoilage. At the same time, water is used more often. If used repeatedly, pathogenic microbial spores on the surface of vegetables will contaminate the water quality. Due to these shortcomings, foreign applications are not common and are only limited to the Water, such as carrots, radishes and other root vegetables. 3, ice cold ice in melting, can absorb a lot of heat, cold water is more effective than the refrigerant, but the ice is expensive, and inconvenient to operate, this method of pre-cooling, there is no universal promotion. 4. Vacuum pre-cooling is a pre-cooling method developed in the United States. It is different from other pre-cooling methods. Instead of using refrigerant, vegetables are put into a vacuum tank. Vacuum is used to depressurize the tank. The moisture in the vegetables is evaporated, and the latent heat of evaporation is taken away, causing the vegetable temperature. When the pressure in the tank falls below the 20 mm mercury column, the temperature of the vegetable begins to drop. When it is reduced to the 3-4 mm mercury column, the temperature can drop to 0-5°C. At this time, the water loss is 2-3%. This pre-cooling method has a pre-cooling speed of 10-30 minutes, while other pre-cooling methods require 2-20 hours. In addition, the vegetables are not wet and the temperature is evenly reduced. In addition to the plastic film sealed packaging, no matter what kind of containers are used for packaging vegetables. However, the large investment in equipment construction technology is complex and the cost is high. It is more economical for leafy vegetables with large surface area and easy evaporation of water. In addition to pre-cooling, the circulation fresh-keeping technology has made new progress in research on liquid nitrogen preservation and vertical preservation. 1. Liquid Nitrogen Preservation Liquid nitrogen can remove heat from stored vegetables and create an atmosphere that is an ideal circulation preservation technology. Liquid nitrogen preservation is suitable for cold storage where other refrigeration equipment cannot be installed, and the application is very convenient. However, the cost is high and the purpose has not reached the level of commercialization. 2. The preservation form of vertical fresh-keeping vegetables has a significant effect on the quality and freshness of vegetables. According to the Japanese test, the same sweet corn has the same other conditions in the circulation process, but the stacking form is different, and the preservation effect is very different. There is heat in the carton placed horizontally, but not in the vertical one; the total sugar content and ATP content of the granules are horizontally lower than those placed vertically. The horizontal arrangement of Dendrobium officinalis and A. sphaerocephala will cause bending and affect the commodity shape. After spinach is placed horizontally, nutrient loss is large, and the chlorophyll content is also low.

Vitamins are organic compounds and vital nutrients that an organism requires in limited amounts. An organic chemical compound (or related set of compounds) is called a vitamin when the organism cannot synthesize the compound in sufficient quantities, and it must be obtained through the diet.

Your body needs them to work properly, so you grow and develop just like you should. They are essential for the normal growth and development of a multicellular organism. Once growth and development are completed, vitamins remain essential nutrients for the healthy maintenance of the cells, tissues, and organs that make up a multicellular organism; they also enable a multicellular life form to efficiently use chemical energy provided by food it eats, and to help process the proteins, carbohydrates, and fats required for respiration.

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