A new method for quick-freezing fruits and vegetables

Quick freezing is a fast frozen cryogenic preservation method. The so-called quick-frozen fruits and vegetables are the frozen fruit and vegetable raw materials that are to be solved, frozen to be frozen, and then retained at a low temperature of -18°C to -20°C. Quick-freezing and preservation is an ideal method for preserving the original flavor and nutrient components of fruits and vegetables in current fruit and vegetable processing preservation techniques.

First, the raw materials for processing frozen fruit and vegetables must be fully matured, and the colors, aromas, and flavors can fully emerge. The texture is crunchy, and there is no pests and diseases, no mildew, no aging yellow, no mechanical damage to the fruits and vegetables as processing raw materials, it is best to do Harvested on the day and processed in time to ensure product quality.

Second, fruits and vegetables that have just been harvested by pre-chilling usually have atmospheric heat and released respiratory heat. To ensure quick freezing, it must be pre-cooled before quick freezing. The method is air-cooled and cold-water-cooled. The former can be cooled with a blower fan, and the latter can be cooled directly by soaking or spraying with cold water.

3. The fruits and vegetables that are washed and harvested usually have dust, silt and dirt attached to their appearance. To ensure that the product meets food hygiene standards, it must be cleaned before freezing. This is especially true for fast-cooled fruits and vegetables, as the quick-frozen products are no longer cleaned when they are eaten, so this cleaning is very important and must not be ignored. In addition to manual cleaning, washing can also be performed with a washing machine (such as a rotating drum, a vibrating mesh belt washing machine) or a high-pressure water jet.

Fourth, cut some frozen fruits and vegetables need to peel, go to the fruit handle or roots and can not use the seeds, tendons, etc., and the larger individual cut into roughly the same, so that packaging and freezing. The slicing can be performed manually or mechanically, and usually the veggies can be cut into pieces, pieces, strips, segments, silk, and the like. Guiqiu thin and uniform, the same length, uniform specifications. Varieties of berries are usually not sliced, but only whole fruit is frozen to prevent loss of juice.

5. Blanching and blanching is mainly used for the quick-freezing processing of vegetables. The goal is to inhibit the enzyme activity, soften the fibrous tissue, remove spicy and astringent tastes, etc. for cooking and processing. Quick-frozen vegetables are not all varieties should be blanched, according to the difference between different species. Generally speaking, vegetables that contain more cellulose or are used to stew or simmer, such as beans, cauliflower, mushrooms, etc., have a good effect after blanching. Some varieties such as green peppers, cucumbers, spinach, tomatoes, etc., containing less fiber, crisp texture, it is not suitable for blanching, otherwise it will make the body soften, lose brittle, poor taste. Blanching 90-100 °C, product temperature should reach 70 °C or more. The blanching time is usually 1 to 5 minutes. After blanching, it should be quickly picked up. Immediately put it in cold water to cool, so that the product temperature can be reduced to 10-12 °C for use.

Sixth, the vegetables after the water splitting, whether or not it has been blanched, its appearance is often accompanied by a certain amount of water, if not removed, it is easy to form a block in the freezing, which is not conducive to quick freezing, but also is not conducive to post-freezing packaging. So you must drain before quick freezing. There are many ways to drain the vegetables. The vegetables can be placed in a bamboo basket on a shelf or placed in a flat and flat place, allowing them to dry naturally; the centrifugal dryer or vibrating screen can be used to drain vegetables.

Seventh, fast frozen vegetables after draining or loading the basket, you need to quickly freeze. In the shortest possible time, the vegetable body will be able to quickly freeze quality after the ice crystal formation stage. Only the cold and rapid cooling will cause the water in the vegetable body to form tiny crystals without damaging the cell tissue. The peeled, cut, blanched or other resolved raw materials are usually promptly frozen at a low temperature of -25°C to -35°C, and then packed and stored again.

Eight, packaging and packaging is an important condition for the storage of frozen fruits and vegetables, its role is: to avoid the formation of monotonous situation due to the evaporation of the surface moisture of fruits and vegetables; to avoid oxidation and discoloration due to contact with air in product storage; to avoid air pollution (dust, slag, etc.), Maintain product hygiene; easy to transport, sell and eat. A lot of packaging containers, usually tin cans, cardboard boxes, cellophane, plastic film bags and large barrels and so on. Sealed after filling, vacuum sealed packaging is ideal. Packaging specifications can be based on the supply object, zero-selling, usually 0.5 kg or 1 kg per bag, hotel and hotel, can hold 5-10 kg. If it cannot be exported in time after packing, it must be stored in a cold storage at -18°C. The storage period varies depending on the variety. For example, beans, kale, etc. can be refrigerated for 8 months; cauliflower, spinach and green peas can be stored for 14-16 months; Carrots and pumpkins can be stored for 24 months.