Generally speaking, the loss of vegetables from production to sales is more than 30% due to unsalable and rotten reasons. It is very difficult for single new technology to increase the yield of vegetables by 30%, but the loss can be reduced through the processing of vegetables, thus increasing the quantity of vegetables relatively. Judging from the varieties of vegetable processing, China's current production and export mainly include fresh-keeping vegetables, pickled vegetables, dehydrated vegetables, quick-frozen vegetables and canned vegetables. Among these processed varieties, fresh-keeping vegetables, pickled vegetables and dried vegetables dehydrated by traditional techniques are the main ones. Dried vegetables 1. Raw material requirements Most vegetables can be used for dry processing. Vegetables with thick meat, dense tissue and little crude fiber are most suitable for drying. For example, potatoes, mushrooms, carrots, green peas, green beans, eggplant, peppers, onions, bamboo shoots, kale, day lilies, etc. Some varieties of the same vegetable are more suitable for drying, such as onions with white bulbs and green cabbage with high solid content. A few vegetables are not suitable for drying because of their unique chemical composition or tissue structure. For example, asparagus will lose its crisp and tender quality after drying, and its tissue will become tough and inedible; Cucumber is rich in water, crisp and fragrant, so it is not suitable for drying. The taste and flavor of dried lettuce are not good; Because of the high moisture content of tomatoes, the juice loss is great during processing. Even if tomato powder is made by spray drying, the quality of finished products will be affected by its strong hygroscopicity. Therefore, in order to make the quality of dried products excellent, it is necessary to choose suitable vegetable varieties and varieties. Dried vegetables have certain requirements for raw materials. The raw material requirements and suitable varieties of several common dried vegetables are introduced as follows: 1, day lily. Raw materials should be orange yellow, about 10 cm long, with fully developed buds, harvested when the flowers are not open, and the sugar content is above 10%. Suitable varieties are Jingzhou flower in Henan, Camellia japonica, Dali flower in Shanxi and Dawuzui in Jiangsu. 2. Carrots. Raw materials require smooth surface, few fibrous roots, inconspicuous pith, dry matter greater than 1 1%, sugar not less than 4%, and high carotene content. Suitable varieties are Shanghai Nanjing Red and Shaanxi Persimmon Red. 3. Onions. Raw materials require large bulbs, compact structure, small neck, all white or light yellow scales, strong spicy taste, and harvesting when the skin is fully dry. The suitable variety is Nanjing Huangpi. 4. Cabbage. The raw materials require large and compact balls, small heart, wrinkled leaves, high dry matter and sugar. Suitable varieties are yellow-green ones, and crew cut varieties are good. 5. Mushrooms. The raw materials require that the mushroom body should be white, thick and tough, the diameter of the mushroom cover should be less than 3 cm, and the edge of the mushroom cover should be rolled in, and the mushroom cover should be harvested when there is little or no wrinkle. Suitable varieties are white mushrooms. 6, sword beans. The raw materials should be turquoise, fresh and tender, and the meat should be thick and gluten-free, and the seeds in the pod have not yet formed or are only in embryonic form. Suitable varieties are white flowers and seeds, safflower and black seeds. 7. Bamboo shoots. Raw materials are required to be white in color, soft and plump in meat, without obvious bitterness, and harvested when bamboo tips are exposed to the ground 17 cm. Suitable varieties are bamboo shoots. Second, the process flow 1, raw material selection. The requirements of vegetable drying for raw materials are high dry matter content, less crude fiber and waste, high edible rate, suitable maturity, freshness, good flavor, no rot and serious damage. 2, cleaning. Manual cleaning or mechanical cleaning is used to remove the sediment, impurities, pesticides and microorganisms attached to the surface of raw materials, so that the raw materials can basically meet the requirements of dehydration processing and ensure the hygiene of products. 3, finishing. Remove inedible parts and unqualified parts such as peeling, roots and old leaves, and cut them properly. Removing the skin of raw materials can improve the edible quality of products and is beneficial to dehydration and drying. Cutting adopts mechanical or manual operation to cut raw materials into certain sizes and shapes so as to evaporate water. It is often cut into pieces, strips, grains and silk, and its shape, size and thickness should be based on the specifications of different types and exports. For some vegetables, such as onion and garlic, it is necessary to rinse the gum juice continuously with water during slicing until the gum liquid is rinsed clean, so as to facilitate drying and dehydration and make the product more beautiful in color. 4, color protection. Dehydrated vegetables are blanched for color protection. Some raw materials are still treated with sulfur to protect their color after blanching or drying. 5. dry. The best drying methods are freeze drying, vacuum drying and microwave drying. However, considering the cost, economic benefits and other factors, air drying equipment is the most widely used in vegetable drying at present. Of course, natural drying method can also be used. 6. Post-processing. After the vegetable raw materials are dried, some of them can be packaged directly after cooling, while others need to be softened, selected and pressed. Softening is also called soaking. Because of the uneven distribution of hot air during drying or the uneven cutting and spreading of raw materials, the water content of products is often slightly different. Therefore, after the product is slightly cooled, it is immediately put into a closed tinplate barrel with a cover or a box covered with plastic bags, keeping a certain distance, which is convenient for the moisture balance of the product, soft in texture and convenient for packaging, storage and transportation. Selection is to remove the broken particles and impurities in the product after softening or before softening, and then pour it into the sorting table to remove the unqualified products. The selection operation should be rapid to prevent the products from absorbing moisture and moisture rising. The selected finished products need to be tested for quality and moisture, and those who fail to pass the test need to be re-baked. Pressing is mainly aimed at dehydrated vegetables. After dehydration, leafy vegetables are fluffy and bulky, which is not conducive to packaging and transportation, so some need to be compressed. Generally, the vegetables are pressed while they are hot just after drying. In terms of packaging and storage, corrugated paper boxes are generally used for packaging, and the boxes are lined with moisture-proof aluminum foil bags and plastic bags for sealing. For products that are easy to be oxidized and browned, they need to be packaged with composite plastic bags and aluminum foil bags, retail packaging is packaged with100g, 250g, etc., and then packaged with cartons, each with a net weight of 20kg or 25kg. After packaging, it is best to store the product in the cold storage around 10℃. The storeroom must be dry, cool, free of peculiar smell and pests. During storage, the water content and pests of finished products should be checked regularly. Canned vegetables 1. Raw material requirements Although most vegetable raw materials can be processed, the processing adaptability is very different, and improper selection of raw materials will affect the quality of products. When selecting canned vegetable raw materials, we should consider the yield, supply period, storage period, the proportion of edible parts, physical properties, chemical composition and sensory quality. Vegetables for canning require varieties and varieties with rich meat, tender and delicate texture, less crude fiber, more edible parts and good color. The following introduces the quality requirements of several canned vegetables. 1, concanavalin. Raw materials are fresh and full, green or light green, pods are round and stick-shaped, not bent, mature moderately (at milk stage), free from diseases, insect pests and mechanical injuries. Flat, deformed, rusty, moldy pods with thick tendons, red flowers and protruding beans are not allowed. 2. Green peas. The pods are fresh and full, turquoise, moderately mature (that is, full of green pods), without pests and mechanical injuries. The pods are green and tender, with more sugar and less starch. Use white flowers instead of red flowers. Each pod contains more than 5 beans, and the raw materials shall not exceed 24 hours from harvest to production. 3. Mushrooms. The seedling body is fresh, the mushroom color is white, there are no mechanical injuries and pests, the umbrella is allowed to be slightly speckled, slightly deformed and slightly thin, there is no opening of the umbrella, there is no odor, the cut of the stalk is flat, there is no space center, there is no mud root, and the length is not more than 1.5 cm. 4. tomatoes. Bright red tomato with fresh and full fruit, no pests and mechanical injuries, no serious deformity, mildew and deterioration, thick flesh, few seeds, solid tissue and soluble solids above 4%. The transverse diameter of the whole tomato fruit is 30-50 mm, and the transverse diameter of the tomato paste fruit is more than 35 mm. 5. Bamboo shoots. Winter bamboo shoots are fresh, crisp and tender, the meat is milky white or light yellow, and there are no pests and diseases. Slight damage is allowed to the thick and old parts of the tender stems, but it is not allowed to hurt the bamboo shoots; Spring bamboo shoots are fresh and good, the meat is white or yellow-white, slight jointing is allowed, and the bamboo shoots are free from obvious cavities, deformities and shrinkage. 6. Asparagus. The required length is12-16 cm, and the average length of the stem is lo-36 mm. First-class products should be fresh and tender, complete and good in shape, white and compact in tip. A small number of bamboo shoots are allowed to have light cyan or purple not exceeding 5 mm, without sediment, hollowness, cracking, deformity, diseases and insect pests, rust spots and other damage. If the light blue or purple part of the head is more than 5 mm, but less than 40 mm; Or the whole head, the length is less than 12 cm, but more than 5 cm; Or there are slight bends, cracks and small hollows; Or there is slight mechanical damage at the tip below 40 mm, they are all second-class products. 7. Lettuce. It is required to be fresh, tender, free from rot, black heart, hollow, hard heart and mildew, with skin tendons removed. After salt soaking, the meat is crisp and tender, without obvious green and bitter odor, and it is light yellow or light green. Second, the processing technology 1, raw material selection. The variety of vegetables used in canning is extremely important. Different products have their own varieties which are particularly suitable for canning, such as mushrooms, tomatoes, green beans and peas. Each raw material requires a certain degree of maturity, and different varieties require different degrees of maturity, such as green beans, peas, sweet corn, etc., and tomatoes require full maturity. The fresher the raw materials, the better the quality of the processed products. Therefore, the time from harvesting to processing of vegetables should generally not exceed 24 hours, and some vegetables such as peas and sweet corn should be processed within 6 hours. 2. Select and grade. Reject unqualified raw materials such as rot, pests and diseases, deformity, insufficient maturity or over-ripening. In order to ensure the quality of canned products, facilitate processing operation, improve labor efficiency and reduce raw material consumption, it is necessary to grade according to the size, maturity and color of raw materials, so that the quality of each batch of raw materials is basically the same. If classified according to shape and size, mechanical classification can be used, and the classifier includes vibrating type and drum type. If the raw materials are graded according to their quality, they are generally graded manually on the workbench or on the conveyor belt. 3, cleaning. The purpose is to remove dust, silt, dirt, residual pesticides and some microorganisms attached to the surface of raw materials, and clean them manually or mechanically. Different washing methods should be adopted for different kinds or properties of raw materials. Generally, it is soaked in flowing clean water first, so that impurities such as sediment on the surface can be easily separated and removed, and then washed under the condition of blowing in water or rinsed with high-pressure water.

For vegetable raw materials with residual pesticides or contaminated microorganisms on the surface, they can be soaked in 0.5%-1.0% hydrochloric acid solution or 0.1-0.2% potassium permanganate solution or 0.06% bleaching powder solution for 3-5 minutes, and then washed with running water. 4, finishing. Remove the inedible part of the outer skin, keep the appearance of the peeled fruit bright and clean, and prevent the peeling from being too thick and increasing the consumption of raw materials. The general peeling methods include manual, mechanical, thermal and alkaline methods. Different varieties of fruits and vegetables have different peeling methods, such as peeling potatoes with lye. Raw materials treated with alkali liquor must be cleaned with running water immediately after peeling to prevent discoloration. 5, color protection. Some vegetables will brown quickly when exposed to air after peeling. After peeling, they must be put into 0. 1% citric acid solution or1%-2% salt solution to protect the color immediately. 6. Segmentation. Slice, dice or cut raw materials according to different types of raw materials and product requirements. 7. Pre-cooking. Most vegetable raw materials must be pre-cooked before canning; Its main purpose is to soften the tissue, facilitate canning and eliminate the air in the raw material tissue; Destroy the activity of enzyme, stabilize the color, improve the flavor and texture, remove part of the water, and keep the stability of open can and solid shape; Kill some microorganisms attached to raw materials. 8. Sorting and canning. Sorting according to quality requirements, and canning vegetables with different colors and sizes separately. The amount of vegetables in each can is adjusted according to the product requirements, such as the open-can solid content, raw material variety, tenderness, pre-cooking, dehydration rate after sterilization, etc. When canning, the soup must be filled up to prevent the top gap in the can from being too large, causing oxidation rings or discoloration of vegetables exposed to the liquid surface. 9. Exhaust sealing. The canned food filled with soup must be quickly heated, exhausted or sealed. Those who heat the exhaust should pay attention to the exhaust time and temperature to make the center of the can reach above 80℃; For varieties with slow heat conduction, the hotter they are before canning, the hotter they are after canning, and the boiling water is added before exhausting; Seal immediately after exhausting; During the exhaust process, steam condensate should be prevented from dripping into the tank, and the exhaust seal should be adopted after exhaust sealing or pre-sealing. When vacuum sealing, the vacuum degree should meet the requirements. 10, sterilization and cooling. After sealing, the canned food immediately enters the sterilizer for sterilization, and the specific sterilization conditions vary with each variety. Most canned vegetables are foods with low acidity or close to neutrality, and most of them are sterilized at high temperature because there are many opportunities for raw materials to be contaminated by heat-resistant Bacillus in the soil. After sterilization, the canned food must be cooled quickly to prevent the continued heating from affecting the content, shape and taste, and to prevent the development and growth of thermophilic spores. Generally, the back pressure is used to cool down for about 5 minutes, and it is appropriate to cool to the central temperature in the tank of 37℃. 1 1, test. According to the quality standards, test methods, inspection rules and packaging requirements of canned fruits and vegetables.