Fresh keeping technology of the hottest winter juj

Fresh keeping technology of winter jujube fresh-keeping packaging

I. winter jujube varieties

1 Zhanhua Winter Jujube: also known as Lubei winter jujube and apple jujube, it is a rare late maturing fresh food variety with the best quality at present, and it is also the main winter jujube variety for current production, promotion and development. It is mainly distributed in Wudi, Zhanhua, Huimin and other places north of the Yellow River in Shandong, and also in Huanghua, Yanshan and other places in Hebei. The fruit of this variety is medium to large, and its shape is similar to that of apple. The average fruit weight is 14-16 grams, and the maximum fruit weight is 23.2 grams. The peel is thin and crisp, and turns ochre red when mature. The pulp is tender and juicy, slightly spicy, and raw without residue. The soluble solid content is 39% - 42%, the water content is about 70%, the edible rate is 96.9%, and the quality is excellent

2. Chengwu winter jujube has a long oval shape and large fruit. The average fruit weight is 25.8 grams, the maximum fruit weight is 32 grams, and the size is neat. The fruit surface is uneven, the peel is thick, and the appearance is dark ochre red. The pulp is thin and crisp, hard, less juice, sweet and strong, the content of soluble solids is 35% - 37%, the edible rate is 97.8%, and the fresh food quality is excellent

3. Xuecheng winter jujube Xuecheng winter jujube is a kind of late maturing fresh food in China. The fruit is round, slightly flat, upright, and highly neat. The average fruit weight is about 22 grams, and the large fruit can be more than 40 grams. The content of soluble solids is 27%, and the edible rate is 97.3%. 6. Measure the size of the sample, the pulp is crisp, the taste is slightly coarse, and the fruit juice content is medium to much. However, this variety has two major shortcomings: first, the fruit quality is poor and the market prospect is not good; Second, some fruits have "extra nuclear" phenomenon, so it is not suitable for large-scale promotion and development

II. Flow chart of preservation of winter jujube

harvesting, packaging and transportation

pre harvest preparation - → harvesting, preliminary distribution - → cold storage pre cooling, graded storage and packaging - sales packaging - → warehousing - → storage management - → cleaning - → ex warehouse - → sales and transportation

III. pre harvest preparation

is mainly aimed at professional households with working capital and refrigeration or air conditioning facilities. Refrigeration equipment and electrical devices should be maintained and overhauled half a month before jujube harvest. First, clean and disinfect the warehouse, and then pre cool the warehouse, prepare sufficient harvest packaging supplies, and inspect the orchard to determine the purchase location and harvest volume

tools or containers in the sequence room can be disinfected by soaking or whitewashing with 0.25% calcium hypochlorite solution, and can also be exposed to the sun if possible; The warehouse can be fumigated with 15g/m3-20g/m3 sulfur for 24-48 hours, or sprayed on the walls and floors with disinfectants such as 1% - 2% formalin, 84 disinfectant, 0.5% bleaching powder, although renewable resources have many advantages. Reduce the temperature to -1 ℃ and keep it stable one week before warehousing

IV. harvesting and preliminary separation

1 Variety: it is very important to select fresh winter jujube varieties suitable for storage. According to statistics, there are 749 fresh jujube varieties, 56 fresh winter jujube varieties and 27 late maturing varieties in China. In addition to Zhanhua Winter Jujube, a large number of developed winter jujube varieties also include Xuecheng winter jujube, Mengyin Snow Jujube, Changle winter jujube and other varieties. Due to the differences in origin and variety characteristics, their storage life is also different, their taste and quality are also different, and the market price is quite different. We should pay attention to the differences when harvesting, and grasp them according to the specific situation. Generally, late maturing varieties are more tolerant to storage than early maturing varieties, and cracking resistant varieties, small fruit shaped varieties or large fruit shaped varieties with loose pulp are tolerant to storage

2. Timely harvesting: the maturity of jujube can be divided into three stages: white ripening stage, crisp ripening stage and full ripening stage according to the changes of skin color and meat quality. In the white ripening period, the chlorophyll of the fruit peel is greatly reduced, the pulp is green white or milky white, and the fruit weight is no longer increased. The winter jujube has good edible quality in this period. The standard tensile sample of the corresponding force value is clamped on the experimental machine for solubility, and the solid content is as high as 25%, and it is rich in vitamin C. During the crisp ripening period, the peel of the fruit gradually turns red from the stem depression and the shoulder. At this time, the fruit is bright, and the pulp is green white or milky white. The pectin material has been decomposed from the original pectin into pectin, making the pulp brittle and the juice increased. At this time, the edible quality is excellent. The fruits at the brittle ripening stage can be divided into three types: primary red fruit (25% coloring), semi red fruit (50% coloring) and full red fruit (100% coloring)

the sugar content of the fruit at the full ripening stage reaches the highest value, a large number of aromatic substances are synthesized, the peel gradually turns purple red, and the fruit stalk is connected with the fruit? The end begins to turn yellow, the pulp changes from green white to milky white, and the near core becomes yellowish brown. The texture gradually softens outward from the near core, and some fruits have a taste of wine. At this time, the jujube fruit has lost its commodity value

the maturity period of winter jujube is from October 5 to October 15, so it is best to harvest in stages and batches in the eyes of Secretary General Ma Zhanfeng, so as to ensure that the stored fruits have uniform maturity and should be completed before the crisp maturity period of jujube fruits. In order to reduce the field heat after harvest, picking should be carried out in the morning or evening when the temperature is low

3. Harvesting method: harvesting is the key process that affects the storage effect. Because the skin of winter jujube is thin and the meat is crisp, it is very easy to form internal injury fruits during fruit picking and handling, which is difficult to distinguish before storage, and it is often easy to cause jujube decay during storage. Therefore, it is strictly forbidden to beat or shake the tree with bamboo poles during harvest. Jujube fruits used for long-term storage should not be sprayed with Ethephon before harvest. The best harvesting method is to manually pick one by one with fruit stalks, because the injury of fruit stalks will also enhance the respiratory intensity of jujube, and those with poor callus effect are also prone to rot. After harvest, it should be handled gently and put into a container with soft liner

4. Preliminary classification and packaging: the harvested winter jujube should be preliminarily classified to select pest fruits, thorn (crush) damaged fruits, non fruit handle fruits, and over mature fruits. As a long-term fresh-keeping fruit, it should be graded according to fruit maturity, and short-term turnover fruit can be graded according to size. Small fruit baskets can be used for picking and packaging. Plastic turnover boxes, cartons and other pressure resistant packaging materials should be used for transportation and packaging. Plastic bags and plastic paper can be used for simple packaging to prevent water loss

v. precooling and graded warehousing

precooling is a necessary part of fruit and vegetable storage. It is better to cool the picked winter jujube to about 0 ℃ within 24 hours, which can reduce the temperature of jujube fruit, release the field heat of fruit, inhibit the respiratory intensity and enzyme activity of jujube fruit, prevent the growth of microorganisms, and prevent the aging of fruit and prolong the storage period

precooling can be carried out by dividing a precooling room (-1 ℃) in the cold storage or directly entering the small cold storage. The storage volume of the small cold storage is controlled at 20% of the total storage capacity each time, so that the temperature amplitude in the storage is not too large. There should be a gap between the boxes to ensure air flow, so that the fruits can be cooled evenly and thoroughly. When the temperature of jujube reaches 0 ℃, it can be packed in 0.04mm-0.06mm thick PVC bags, each bag is 1kg, and 8 holes with a diameter of 5mm are tied on the bag. After binding, it can be refrigerated

jujube fruits stored in controlled atmosphere storage must have a special pre cooling warehouse. When the temperature of jujube fruits meets the requirements, they can be put into the controlled atmosphere storage. At the same time, strictly inspect the stored jujube fruits. Those with decay and trauma are strictly forbidden to bring them in. Because the inspection of the controlled atmosphere storage is inconvenient, once there are rotten fruits, the storage effect of the fruits in the whole storage will be affected

VI. storage period management

1 Temperature: stable low temperature is the key condition for jujube storage. The temperature of cold storage should be between 0 ℃ --2 ℃, the safety temperature should be controlled at ± 1 ℃, the fluctuation of storage temperature should not exceed 2 ℃, and the fluctuation of jujube fruit temperature should not exceed 0.5 ℃. Because the fluctuation of product temperature is easy to cause condensation in the packaging bag, which increases the probability of mold breeding and jujube fruit decay. In addition, the temperature fluctuation will also have a series of negative effects on the physiology of jujube fruit. Therefore, it is necessary to ensure that the temperature in the warehouse is uniform and the temperature setting is stable during storage

2. Humidity: the suitable humidity for storing winter jujube is 90% - 95%. Winter jujube is packaged in fresh-keeping bags, and the temperature in the bags can generally meet the requirements. Automatic humidifier should be used for humidification in the controlled atmosphere storehouse. The moisturizing effect of this method is better than that of manual humidification

3. Gas conditions: for the modified atmosphere fresh-keeping warehouse, the better gas conditions for storing winter jujube are: oxygen 3%--5%, carbon dioxide <2%. When the jujube fruit in the warehouse changes from green fruit to half red and full red fruit, it should be sold. Refrigerated truck or insulated truck shall be used for transportation to ensure that jujube fruits are transported and sold in the cold chain

in a word, in the storage technology, the jujube should be harvested by grades and stages according to the growth and maturity of jujube, and the pre cooling work should be completed within 24 hours. Collision shall be minimized during classification and transportation. During storage, the warehouse temperature shall fluctuate within ± 1 ℃ and the humidity shall be between 90% and 95%. The gas composition is controlled at 3% - 5% for oxygen and less than 2% for carbon dioxide. Timely eliminate the rise of storage temperature caused by insufficient power or power failure in the refrigeration airflow

source: Yima agriculture