Super-sweet corn pre-cooling preservation technology
Supersweet corn has a high sugar content, a sweet and soft taste, and is rich in nutrients. It can also be used as a vegetable in addition to fresh food. It is also a raw material for canning and frozen processing. It is quite popular among consumers and only sweet corn is used. After harvesting, if it fails to effectively reduce the temperature of its ear or inhibit the heat generated by its respiration, any exposure to it will cause the rapid conversion of sugar and reduce the sugar content due to the cumulative effect of heat, greatly affecting its original freshness and quality. And the longevity of flavor and commodity value. Why precooling low temperature is the best way to ease the respiration of sweet corn and other changes that will produce heat, high temperature can promote respiration, generate and accumulate heat energy, and the respiration at 21 °C is about eight times that at 0 °C; The high temperature also accelerates the conversion of sugars. At 30°C, 24 hours, sweet corn loses 60% of its sugars. At 0°C, it loses only 5% of sugars in the same 24 hours. In addition, the high temperature also promotes the reproduction of microorganisms and accelerates. The loss of moisture, which greatly affects the quality of sweet corn, so the management of the temperature of sweet corn after harvest is the key to determine the quality of sweet corn, the demand for pre-cooling, and thus the owner. Precooling mechanism The precooling speed mainly depends on: (1) the difference between ice water temperature and sweet corn temperature; (2) the size of precooled water flow; and (3) the contact area of ​​ice water with the product. The most suitable cold water temperature is zero degrees Celsius, and the water flow rate is 10 liters per square meter per second. For a continuous water cooling system, the product delivery speed is 30 cm per minute. If the batch is fixed system, the product is placed. The rear of the cooling chamber is no longer moved and is removed after the product reaches a relatively low temperature. The method of precooling the precooling method and the cooling system includes forced air cooling, ice water cooling, vacuum steam cooling, and contact cooling with ice. However, the precooling of sweet corn is more appropriate with the cold water cooling method, and the water cooling method is the water spray type. And water immersion type two, water spray type is installed in the product above the nozzle to spray cold water on the bottom of the product, soda through the evaporator evaporator coil to reduce its temperature, can be used repeatedly. Immersion is to soak the product in a flowing stream of cold water. The cooling system is divided into two types. One is a continuous conveyor belt type and the other is a fixed batch type. The continuous type is applicable to a large number of products in a large pre-cooling field and products requiring a short cooling time, such as vegetables, etc. The batch type applies to a smaller amount of product, and it is desirable that the product needs to be cooled for a longer period of time, such as sweet corn. Take immediate action to ensure that the fresh pre-cooling process is not simply putting sweet corn in the ordinary cold store, allowing it to cool slowly to the desired temperature, but instead artificially in the shortest possible time for the characteristics of sweet corn. A technique that cools to a suitable low temperature. By reducing the loss of sugar, Lai inhibits the growth of microorganisms during storage and transportation to prevent spoilage and inhibits the activity and respiration of corn enzymes, and other chemical changes. Pre-cooling can maintain quality without improving quality. Good quality is required. Appropriate harvest, ie during milk ripening or ripening (16 to 31 days after spiting or 85 to 90 days after sowing), avoid excessive accumulation or sun exposure after harvest and send it to the pre-chilled area as soon as possible. In order to prolong its storage life and maintain the quality and freshness of sweet corn in consumers' hands, it is usually necessary to complete it within a few hours of harvesting. Batch fixed pre-cooling steps 1. Grading - After harvesting, sweet corn should be properly graded according to all levels of standards and specifications in order to achieve uniform quality and aesthetics, and to increase product value. In the grading operation, the head and tail of the sweet corn were removed and the excess loquat leaves were removed, leaving only 3 to 4 slices to accelerate the pre-cooling treatment efficiency. 2? loading basket arrangement. When pre-cooling, the placement and direction of the ear directly affect the pre-cooling time of sweet corn, should be upright arrangement, the end of the ear is better in the top. If the ear stalk is placed on the top or the ears are horizontally arranged, the pre-cooling time is 1.5 to 2 times more. Baskets can be made of plastics, but the principles of water circulation on all sides and bottom should be allowed. Each basket can hold about 20 kilograms, but can be stacked in layers to increase the amount of pre-cooling. 3? Pre-cooling. Pre-cooling operation should be made when the ice water temperature reaches O~1C Celsius. The higher the pre-cooling water temperature is, the longer the pre-cooling time is. The 5C ice water needs to be extended compared to 1C ice water pre-cooling time. 1/3 times. The pre-steam time of sweet corn varies depending on the product temperature, and is generally estimated as the semi-cold period or the 7/8 cold period. The so-called semi-cold period refers to the cooling device in the cooling process, the temperature and the cooling media temperature difference to half of the original temperature difference, such as the initial temperature of sweet corn 28C, 1C cold water as the refrigerant sweet corn temperature decreased to 14.5 The time required for C is about 20 minutes for its semi-cold period. And the 7/8 cold period is the time required to reduce the temperature difference to 1/8, which is about three times the semi-cold period time? About 60 minutes? To cool the sweet corn cob center to 4C, it takes about 62 minute. 4. Packing, storage and transportation... The pre-cooled sweet corn should be quickly packed in a low-temperature cold room to avoid affecting the product quality. The sweet corn pre-cooled to 2°C can raise the temperature to 16 at room temperature for 78 minutes. °C, packaging can be used 20 kg plastic bags with carton packaging or 2 spikes or 4 spikes as a small package, small packaging can be styrofoam tray with plastic wrap or directly wrapped in plastic wrap to prevent water loss to ensure quality . It is very important to maintain the low temperature after precooling of sweet corn. Storage and transportation should be carried out at a low temperature. Refrigerated transport vehicles can be used for long-distance transport, and appropriate ice can be added directly to the tank at short distances to maintain low temperature, generally 20 kg. At an atmospheric temperature of 3o°C and a product temperature of 4°C, adding 4 kg of crushed ice can maintain a 24-hour low temperature. In order to ensure the preservation of sweet corn and shorten the shipping time, it should be the best way to direct sales. The ear-upright upright basket is arranged immediately after the pre-cooling and the packaging operation is performed.
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