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Practical technology of winter jujube preservation
First, winter jujube varieties 1. Zhanhua winter jujube, also known as Lubei winter jujube and apple jujube, is currently the best quality rare late-maturing fresh food species, and is also the main winter jujube variety for current production promotion. It is mainly distributed in Shandong Province, north of the Yellow River, Wudi, Zhanhua and Huimin, and other places such as Huanghua and Yanshan in Hebei Province. The fruit of this variety is medium to large, with a fruit shape similar to that of apple. The average fruit weight is 14g-16g and the maximum fruit weight is 23.2g. The skin is thin and brittle, and it turns red after ripening. The flesh is tender and juicy, slightly pungent and raw. Soluble solids content of 39% - 42%, about 70% moisture content, edible rate of 96.9%, excellent quality. 2. The Chengwudongzao has a long oval shape and a large fruit. The average fruit weight 25.8 grams, the largest fruit weight 32 grams, neat size. The fruit surface is uneven, the skin is thick and the appearance is dark red. The flesh is fine and brittle, hard, less juice, sweet and rich, soluble solids content of 35% - 37%, edible rate of 97.8%, fresh food quality and so on. 3. Xuecheng Dongzao Xuecheng Dongzao is a kind of special cooked food in China. The fruit is round and slightly flat, straight and high in orderliness. The average fruit weight is about 22 grams, and the big fruit can be more than 40 grams. Soluble solids content of 27%, edible rate of 97.3%. The flesh is crunchy, the taste is slightly thick, and the fruit juice content is moderate. However, the variety has two major shortcomings: First, poor fruit quality, poor market prospects; Second, some fruits have "nuclear outer nuclear" phenomenon, it should not be widely promoted and developed. II. Fresh-keeping Process of Winter Jujube Harvesting Packaging Transportation Pre-harvest Preparation --- Harvesting, Initial Separation --- Cold Storage Pre-Cooling, Hierarchical Storage, Packaging, Sales and Packaging--→Storage--→Storage Management--→Cleaning--→ Outbound ---> sales and transportation III. Pre-harvest preparation is mainly for professional households with working capital and cold storage or air conditioning facilities. The refrigeration equipment and electrical equipment shall be maintained and overhauled within half a month before harvest. First, the warehouse is cleaned and disinfected, and then the warehouse is pre-cooled to prepare sufficient collection and packaging supplies, and the orchard is inspected to determine the acquisition location and the amount of harvested. Sterilization of prefabricated tools or containers can be soaked or brushed with 0.25% calcium hypochlorite solution, and can also be exposed to sunlight under conditions; the warehouse can be fumigated with 15 g/m3 - 20 g/m3 of sulfur for 24 hours - 48 hours, or use 1% - 2% formalin, 84 disinfectant, 0.5% bleach and other disinfectants spray the walls, the ground. Cool down to -1°C 1 week before storage and keep it stable. Fourth, harvest and initial points Variety selection of fresh winter jujube varieties is critical. According to statistics, China has 749 varieties of jujube, 56 varieties of winter jujube and 27 varieties of late-maturing varieties. In addition to Zhanhua winter jujube, a large number of developed winter jujube varieties include Xuecheng winter jujube, Mengyue snow jujube, Changle winter jujube, and other varieties. Due to differences in origin and variety characteristics, their storage life is also different, and their taste and quality are also different. The market price is quite different. When harvesting, pay attention to the difference and grasp according to the specific situation. Generally, the late-maturing varieties were more resistant to storage than the earlier-maturing varieties, the anti-cracking varieties, the small-fruited varieties, or the looser varieties of the large-fruit-shaped pulp. 2. The ripeness of timely harvested jujube can be divided into three stages: white mature period, brittle ripening period and ripening period according to skin color and meat quality. During the ripening period, the chlorophyll content in the fruit peel was reduced, and the pulp was greenish white or milky white. The fruit weight no longer increased. The winter jujube had good edible quality during this period, and the soluble solids were as high as 25%, and were rich in vitamin C. The fruit of the crispy ripening period begins to turn reddish by the stem and fruit shoulder. During this period, the fruit is bright and the flesh is greenish white or milky white. The pectin material has been decomposed into pectin by the protopectin to make the pulp texture brittle and its juice. Increase in food quality at this time. The fruit in the brittle phase can be divided into three types: red fruit (25% coloring), half red fruit (50% coloring), and full red fruit (100% coloring). In the ripening stage, the fruit's sugar content reaches the highest value, a large amount of aromatic substances are synthesized, and the skin becomes purple, and the end of the connecting stem and fruit begins to turn yellow. The pulp turns from greenish white to milky white, and the near nucleus becomes yellowish brown. The texture gradually softens outwards from the nearer nucleus, and some fruits have a taste of wine. At this time, the jujube fruit has lost its commercial value. The jujube ripening period is from October 5 to October 15, so it is best to carry out the batch in batches at the time of harvesting to ensure that the stored fruits have a uniform maturity and it is appropriate to finish before the crisp ripening period of jujube. In order to reduce post-harvest field heat, picking should be done in the morning or in the evening when temperatures are low. 3. Harvesting methods are the key processes that affect the storage effect. Because the winter jujube skin is thin and fragile, it is easy to form internal injuries in fruit picking and handling. It is difficult to distinguish them before storage, and it often causes jujube rot during storage. Therefore, it is forbidden to beat and shake the tree with bamboo rafts when harvesting. For long-term storage of jujube fruit, it is not advisable to spray ethephon before harvest. The harvesting method is best to manually pick one by one with a handle, because the fruit stem injury will also enhance the respiratory intensity of the jujube, and the poor callus effect is also easy to cause decay. After harvesting, they should be handled lightly and placed in a soft-lined container. 4. The winter jujube harvested at the beginning and the packaging must undergo initial separation to pick out the disease and fruit, thorn (pressure) wound fruit, fruit without handle, and ripe fruit. As a long-term preservation fruit according to the maturity of fruit classification, short-term turnover fruit can be grading by size. Small fruit baskets can be used for picking packaging, and plastic packaging containers, cardboard boxes, and other pressure-resistant packaging materials are used for transport packaging, and plastic bags and plastic paper can be used for simple packaging for preventing water loss. Fifth, pre-cooling cold storage is the necessary part of storage of fruits and vegetables. Picking of the jujube is best cooled to about 0°C within 24 hours, which can reduce the temperature of the jujube fruit, release the heat of the fruit field, inhibit the respiration intensity of the jujube fruit and the activity of the enzyme, prevent the growth of microorganisms, prevent the senescence of the fruits, and prolong the storage period. The role. Pre-cooling can be done by drawing a pre-cooling room (-1°C) in a cold room or directly into a small cold room. The amount of warehousing in a small cold storage room is controlled at 20% of the total storage capacity, so that the temperature within the storage area will not be excessively large, and there must be a gap between the box and the box to ensure air flow and make the fruit cool evenly and thoroughly. When the jujube temperature reaches 0°C, it can be packaged in a 0.04mm--0.06mm thick polyvinyl chloride bag, 1kg per bag, with 8 holes in a 5mm diameter hole on the bag. . The use of air-conditioned storage of jujube fruit, there must be a dedicated pre-cooling room, wait for the jujube fruit product temperature to meet the requirements, and then placed in the transfer library. At the same time to strictly check the storage of jujube fruit, rot and trauma are strictly prohibited because of the inconvenience of the air-conditioning library inspection, once the decay of fruit will affect the storage effect of the entire library. Six, storage management Temperature stability and low temperature are the key conditions for jujube storage. Cold storage temperature should be between 0 °C - 2 °C, the safety temperature should be controlled at 1 °C, fluctuations in the temperature of the library should not exceed 2 °C, jujube fruit temperature fluctuations less than 0.5 °C ideal. Because of the fluctuation of product temperature, it is easy to cause dew condensation inside the package, increase the chance of mold breeding, rot of jujube, and in addition, the temperature fluctuations will also have a series of negative effects on the physiology of jujube fruit. Therefore, in the storage process to ensure that the temperature inside the library is uniform and the temperature setting is stable. 2. Humidity storage of winter jujube suitable humidity is 90% - 95%. The use of fresh-keeping bags to package winter jujube, the temperature inside the bag can generally meet the requirements. To humidify the atmosphere, an automatic humidifier is used. The moisturizing effect of this method is better than that of artificial humidification. 3. Gas conditions For modified atmosphere storage, better gas conditions for storage of winter jujube are: oxygen 3% - 5%, carbon dioxide <2%. When the jujube jujube fruit from the fruit to semi-red and red fruit should be sold. Choose refrigerated truck or warm car to ensure the transportation and sale of jujube fruit in the cold chain. In short, in the storage technology, it is necessary to classify and harvest in stages according to the growth and maturity of jujube, and complete the pre-cooling work within 24 hours. The collision should be minimized during grading and transportation. The storage temperature should be within 1°C during storage and the humidity should be between 90% and 95%. The gas composition is controlled in oxygen: 3% - 5%, carbon dioxide: less than 2%. It is necessary to promptly eliminate the increase in the temperature of the refrigerated air stream due to power shortage or power outage.