Sweet corn is the representative of new special corn breeding products in my country, and its sugar content is generally 3-6 times that of ordinary corn. According to the difference in sugar content and genotype, it can be divided into ordinary sweet corn, enhanced sweet corn and super sweet corn. Ordinary sweet corn has a sugar content of about 10-15%, more water-soluble polysaccharides, and has a waxy and good flavor. On the basis of ordinary sweet corn, the enhanced sweet gene was introduced to breed enhanced or semi-enhanced sweet corn, with a view to improving its sweetness and flavor. Supersweet corn has 30% sugar content and is extremely sweet. After harvesting, the conversion of sugar into starch is slow, so the requirements for the harvest period are not very strict.
In addition to the high sugar content of sweet corn, protein, amino acids, fat, dietary fiber, vitamins and other ingredients are higher than ordinary corn. Sweet corn is an economic crop that integrates grain, fruit, vegetables and feed. In addition to the direct supply of “green bracts” to the market, sweet corn ears need to be processed quickly to maintain the high sugar content and freshness of sweet corn. Sweet corn products include: canned sweet corn, quick-frozen sweet corn, dehydrated sweet corn, sweet corn beverages, canned sweet corn shoots, etc. Canned sweet corn is one of the largest canned vegetable varieties in the world, second only to canned asparagus. At present, the annual output of canned sweet corn and sweet corn products worldwide has exceeded one million tons, and the annual international trade volume reaches 250,000 tons. The average American consumes 6.1 kg of canned sweet corn, 3.2 kg of fresh sweet corn, and 1.2 kg of frozen sweet corn. Due to various reasons, my country’s sweet corn industry is still in its infancy, and sweet corn products still cannot meet the market needs. Canned sweet corn and quick-frozen sweet corn required for domestic medium and high-end restaurants and hotels have to be imported from abroad. Therefore, from improving the living standards of urban and rural people, increasing the farmers’ means of prosperity and the need to earn foreign exchange through exports, the sweet corn industry should be vigorously developed. In this paper, Jintian Fruit and Vegetable, a manufacturer of quick-frozen sweet corn, introduces canned sweet corn kernels and processing technology of quick-frozen sweet corn kernels.
(1) Canned sweet corn kernels. The main equipment for processing canned quick-frozen sweet corn kernels are: thresher, vacuum sealing machine, steam interlayer pot, autoclave, etc.
Process flow: raw material picking → pre-cooling → peeling bracts, removing whiskers → threshing → rinsing → pre-boiling → cooling → canning → injection of soup → vacuum sealing → sterilization & rar agricultural news; insulation inspection → packaging → Product storage.
(2) Technical points:
① Raw materials. Harvest ears of sweet corn that are moderately mature and fresh, with soft and full grains, free from diseases and insect pests;
②Cool. Greatly reduce the warmth of sweet corn in the field. Since the sugar content of the ears with bracts is more stable than that of peeling bracts, in order to ensure the quality, they should be harvested and processed in time. If it can’t be processed in time, it should be preserved at low temperature with bract leaves; It is required to remove the bract leaves and silks;
④ thresh. It is an important part of the process. Machine threshing is used. In the operation, the benchmark of the center hole of the tool should be adjusted in time to ensure the integrity of the sweet corn kernels, and the thresher should be cleaned in time;
⑤ cleaning. To wash away the crushed sweet corn kernels and residual silk and impurities;
⑥ pre-cooking. It is the key process of processing, the purpose is to inhibit the enzyme activity and sterilization in sweet corn, and maintain the unique color of sweet corn. Generally, sweet corn kernels can be cooked in water at 90-95°C for 5 minutes. Then perform vibration draining or low speed dehydration. The next steps are canning, soup injection, vacuum sealing, high temperature sterilization, 37℃ thermal insulation inspection, labeling, and finished product storage.
At present, there are only enterprise standards for canned sweet corn, industry standards and national standards have not yet been formulated.
(2) Quick-frozen sweet corn on the cob (corn kernels)
(1) Process flow: raw material picking → pre-cooling → peeling bract leaves to be shaved → cleaning → sorting → cutting (threshing) → pre-cooking → cooling → selection → draining → quick freezing → weighing, packaging → inspection → boxing →Refrigerated in storage.
(2) Technical points: The first part is similar to the processing of canned sweet corn.
① Sorting. On the conveyor belt in the sorting room. The standard of semi-finished products used for quick freezing of whole ears is higher, and other ears of sweet corn are used for processing quick frozen sweet corn kernels;
② Cut into sections. Take the middle corn. The head and tail are cut on the stainless steel segment cutting machine, and the cut is required to be flat and smooth, and the length is consistent. The method of threshing is the same as canned sweet corn;
③ The pre-cooked quick-frozen sweet corn kernels are cooled, selected, and drained into the quick-freezing process;
④ quick-frozen. The key is to make the corn pass through a large ice crystal formation zone of 0~-5℃ at a fast speed when freezing, so that most of the water in the corn becomes tiny ice crystals under 100 microns, and the center temperature reaches -18℃ In order to maintain the original color, aroma, taste and nutritional value of food to a great extent. For quick-frozen sweet corn kernels, if a single quick-freezer is used, the freezing time is generally 10-15 minutes. For the sweet corn cob section, a low-temperature quick freezing room can be used, and the freezing time is generally 30 minutes or longer.
⑤ Packing weighing, inspection, boxing and other processes are carried out in a low-temperature (about 5 ℃) packaging room. Send to a low temperature store below -18℃ for storage and sale.