On the packaging, storage and preservation of the

2022-08-08
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Packaging, storage and preservation of Longjing tea (Part 1)

Longjing tea is one of the famous historical teas in China, and its unique color, flavor, quality and style are well-known at home and abroad. Especially in recent years, Longjing tea has been widely recognized by the market, and its production and sales volume have increased year by year, becoming the famous and high-quality green tea with the largest production and sales volume. However, improper storage of Longjing tea during storage and transportation will directly affect its quality, resulting in a significant decline in economic value and drinking value. Therefore, producers and consumers attach great importance to the storage and preservation of Longjing tea. Longjing tea has fine production, complex processing technology and high economic value, but the corresponding storage and packaging methods are relatively backward. Compared with tea packaging in Japan, Taiwan and other domestic food packaging, Longjing tea packaging is relatively simple and poor in fresh-keeping effect. From the storage and packaging methods of Longjing tea in the market, most small packages are packed in iron cans, paper cans or general plastic composite bags, and the barrier performance of the packaging is poor. At the same time, there are also some problems in the mass storage of Longjing tea and the storage in the process of household consumption. Therefore, this paper briefly introduces the quality change mechanism of Longjing tea during storage and the fresh-keeping methods in different occasions without oil leakage

I. quality deterioration mechanism and related fresh-keeping technology of Longjing tea

the quality deterioration mechanism of Longjing tea is the same as that of ordinary green tea. Studies at home and abroad have shown that temperature, moisture, oxygen and light are the four factors that affect the quality of stored green tea. The automatic oxidation of chemical components in tea is the fundamental reason for the deterioration of tea quality; Moisture and temperature are the conditions of quality change, which can accelerate or delay the oxidation reaction speed; Light can change the quality of tea, promote the oxidation of pigments, lipids and other compounds, and have a certain decomposition effect on tea components. The most easily oxidized components in Longjing tea are: aroma components. Chlorophyll, vitamin C and polyphenols. According to these research results, drying technology was used in tea storage. Low temperature refrigeration technology. Vacuum deoxidization and controlled atmosphere technology and other fresh-keeping technologies

1. Drying technology

drying technology is a traditional tea storage technology, which generally uses lime. Charcoal, silica gel, etc. are stored together with tea, which has a certain effect. Theoretically, moisture has a great impact on the quality of tea. The moisture content of dry tea should be as low as possible, generally less than 6%. The relative humidity of the environment has a great influence on the moisture content of dry strips. Generally, the relative humidity of the storage environment should be less than 60%. Drying technology is to extend the quality of tea. Preservation period and the premise of applying other preservation technologies

2. Low temperature refrigeration technology

the reaction speed of the chemical components contained in tea is closely related to temperature. Reducing the temperature can slow down most chemical changes, thus inhibiting the changes of the substances contained in green tea and maintaining its color, flavor and other sensory qualities. A large number of research results at home and abroad show that among the existing tea preservation technologies, low-temperature refrigeration technology is the most advanced and has the best effect. Considering the fresh-keeping effect and cost saving, it is better to control the low-temperature refrigeration temperature of Longjing tea at 0-10 ℃

3. deoxygenation and air extraction and nitrogen filling packaging technology

the relevant research results at home and abroad show that oxygen is required to participate in the changes of various biochemical components in tea during storage. Therefore, the aging process of tea can be inhibited under anaerobic and hypoxic conditions. On the basis of this research, deaerator deaeration and air extraction and nitrogen filling packaging technology are adopted. It is generally believed that green tea adopts deoxidizing agent and air extraction and nitrogen filling packaging technology. On the one hand, the effect of material deformation and residual stress caused by humidity induced expansion is significant, which can reduce the change degree of sensory quality of green tea, enhance the storage performance of green tea, and extend the effective storage period

4. Other technologies

in recent years, some new fresh-keeping technologies have emerged. For example, the method of adding fresh-keeping substances before or during green tea processing has a certain effect. Biological fresh-keeping technology is also a development direction of tea storage and fresh-keeping

II. Storage and preservation technology of large package tea after Longjing tea

most places are almost blank. 1. Storage in a dry and odorless warehouse

this method is simple and easy, with low use cost and certain effect. It is suitable for manufacturers with relatively poor economic conditions or storage of medium and low-grade tea. Generally, five times of drying is adopted, and dehumidifiers can also be used if conditions permit. Those with large storage capacity are generally paved with massive quicklime on the bottom layer and large packages of tea on the upper layer; When the number of storage strips is small, it can be packed separately, such as in boxes, bags, etc., that is, Longjing tea packaged with kraft paper can be stored together in boxes or bags containing lime. The amount of lime should be determined according to the water content of tea, and the ratio of tea to quicklime is generally 4-5:1. During the use of this method, attention should be paid to observation. Lime should be changed frequently, at least 3-4 times a year

2. Adopt the special cold storage for tea to refrigerate

according to the existing fresh-keeping technology, low temperature cold storage is the most effective way to solve the storage and fresh-keeping of large quantities of Longjing tea. Low temperature refrigeration can keep tea under low temperature conditions, avoid light and dehumidification, and greatly extend the shelf life of tea. The only disadvantage is that the equipment investment is large and the use cost is high. In terms of form, the combined cold storage and fixed civil cold storage are mainly used for cold storage of tea. The combined cold storage has a relatively small volume (l-100m2), can be disassembled and assembled, flexible and flexible installation, good heat preservation, safety and convenience, but the price is relatively high, so that the sealing cone enters the pouring room until the wedge is detained and locked, which is suitable for small tea enterprises and retail departments to store high-grade Longjing tea. The civil cold storage has a relatively large volume and can only be used for fixed purposes, but the investment is relatively small, and there is a large choice of refrigeration equipment, which is suitable for large-scale storage of Longjing tea. The refrigerating capacity of the cold storage should be determined according to the size of the warehouse and the amount of tea stored. Generally, it should be equipped with an automatic temperature regulation system to make the refrigeration system and the cooling system work synchronously, with the function of automatic temperature regulation and dehumidification. Considering the quality assurance effect and economic benefits of cold storage operation, it is appropriate to control the tea storage temperature at 0-8 ℃ when the relative humidity is controlled to 65%

during the cold storage of Longjing tea, due to the large temperature difference inside and outside the warehouse, there should be a transitional treatment for both warehousing and outbound. Before entering the warehouse, put the tea in the precooling chamber for precooling, and then send it to the cold storage room. When leaving the warehouse, put it in the transition room with relatively high temperature for a few days before leaving the warehouse

before the storage of tea, especially before the initial use of the new cold storage, or when the relative humidity in the storage exceeds 65%, ventilation and dehumidification should be carried out in time. After long-term use of the cold storage, there will be peculiar smell in the storage, which is harmful to the quality of tea. It is necessary to change the air in time. Generally, the storage should be thoroughly cleaned once every 2-3 years to keep the storage clean and the air fresh

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