The Application of Vacuum Packaging Technology in the Fresh-keeping of Persimmon Fruit

Persimmon fruit is nutritious and has important medical value and health care functions. However, most of the traditional persimmon fruit growing areas in China are astringent persimmon, and the representative variety is Mopan persimmon. The content of soluble tannins in Shibuya persimmon fruit is high, and the food has a strong astringent taste. Therefore, the exploration of persimmon fruit peeling and astringent preservation technology is a top priority for the persimmon fruit industry in China.

1, the status of domestic vacuum packaging technology

At present, the processing and preservation of food, oilseeds, fruits, vegetables, livestock and poultry, and aquatic products are still in a low-level and extensive state, and China's refrigerated conditions cannot be compared with developed countries such as the United States and Japan, resulting in a large number of agricultural products. Loss and waste of resources. Persimmon fruit loss accounts for 20% of China's annual production. The vacuum packaging persimmon fruit can maintain the quality and nutrient content of persimmon fruit, and is highly valued by the persimmon fruit industry.

2, the basic principles and characteristics of vacuum packaging

In addition to controlling the outside temperature and sterility of the vacuum packaging, it is more important to control the proper gas environment of persimmon fruit to achieve the desired preservation purpose. Its main methods are mechanical extrusion, straw degassing and other methods. Either way, the air inside the bag must be extracted and then heat-sealed. Its main features are: reduce the oxygen content in the bag, inhibit the growth and development of mold, aerobic bacteria, control persimmon fruit deterioration, to achieve the purpose of preservation and durability. At the same time, persimmon fruit can produce an environment of carbon dioxide through anaerobic respiration, which can effectively reduce the respiration of persimmon fruit, reduce ethylene production and nutrient consumption, remove strong astringent taste, and ultimately it is both astringent and fresh. In addition, after persimmon vacuum packaging, it can also resist mechanical pressure and reduce vibration, which is not only beneficial to long-distance transportation, but also conducive to sales.

3, Persimmon fruit harvesting and classification

(1) Harvesting and grading fruit harvesting should be carried out gently; ensure that the sepals are intact, because sepals are important respiratory organs of persimmon fruit; maturity requirements are consistent, 1989 picks when mature, maturity is different, persimmon fruit is astringent and Preservation is also inconsistent; fruit selection after picking, disease and fruit removal, fruit damage, and oversized and undersized fruit.

(2) Single-fruit packaging Because the size of the packaging bag involves the area of ​​gas penetration, the final proportion of gas in the bag is affected, and it is related to the shelf life of persimmon fruit.

4. Persimmon vacuum packaging equipment and materials

The chamber type vacuum packing machine is used to pack the selected persimmon fruit into a vacuum bag in a plastic bag, and the bag is evacuated to a predetermined degree of vacuum. The heat sealing device is closed and the bag mouth is closed. Vacuum inflatable packaging, first filled with gas before sealing. This vacuum packaging machine has a high degree of vacuum and can adjust the degree of vacuum as needed, and is currently one of the most widely used. Vacuum packaging materials are mostly plastic film, because the film has good barrier properties, safety, chemical stability, mechanical toughness and temperature resistance, and convenient printing, and some have a certain degree of transparency and a certain degree of shading. Plastics are divided into two types: single membrane and membrane. Persimmon vacuum packaging generally uses single membrane.

Relevant studies have shown that the use of low-density polyethylene (LDPE) plastic film vacuum packaging technology to deal with astringent persimmon, persimmon fruit in the hypoxia, high carbon dioxide anaerobic environment for anaerobic respiration, production of ethanol and acetaldehyde, acetaldehyde and persimmon The soluble tannins in the fruit undergo agglomeration reaction, and soluble tannins can be converted into insoluble tannins to achieve the purpose of destringing. Because LDPE has a certain permeability, and persimmon fruit produces carbon dioxide during anaerobic respiration, gas exchange between the carbon dioxide in the bag and the outside air will occur. When the exchange of internal and external gases reaches equilibrium, the gas in the bag will maintain a certain level. The ratio of the gas can be adapted to both the persimmon fruit and the preservation of the fresh fruit by the choice of packaging materials.

5, vacuum persimmon packaging

The degree of vacuum determines the initial oxygen content of the bag, which affects the degree of anaerobic respiration of the persimmon fruit, and thus affects the length of time required for the persimmon fruit to be astringent.

Using a 0.1mm LCPE single-fruit vacuum-wrapped milled persimmon, it takes 7 days to remove the astringent at room temperature, and it can be kept crisp for 50 days without softening. The vitamin C content, fruit color, and fruit flavor remained basically unchanged during storage and no odor was produced. However, when the persimmon fruit is completely softened, the vitamin C content in the persimmon fruit is reduced, and ethanol is produced in the packaging bag. At this time, the taste of alcohol is slightly. The control persimmon without any treatment at room temperature completely softened after 20 days. After the softening, the persimmon is still not fully astringent. It can be seen that the vacuum packaging technology has played a role of double-edged sword on the astringent and persimmon fruits.