After the purification and processing of fruit and vegetable products, the surface tissue cells are destroyed, the area of microbial infection increases, the wound respiration is enhanced, and the nutrient consumption is intensified. Respiration intensity and microbial status are the main factors determining the quality of the clean vegetable shelf life, while temperature is the main external factors affecting respiration intensity and microbial reproduction rate. The higher the temperature, the greater the respiration intensity, the stronger the respiratory metabolism of fruits and vegetables, and the faster the consumption of various nutrients, the result is to accelerate cell decomposition and seriously reduce the storability and disease resistance of fruits and vegetables. Low temperature is the most effective and safest way to inhibit the growth of microorganisms, in the temperature environment below 5 °C, the reproduction of various microorganisms will be significantly inhibited, so as to effectively ensure the quality and freshness of clean dishes. However, not all clean vegetables are suitable for low temperatures, and many vegetables are sensitive to low temperatures and are prone to cold damage. For example, cucumbers, zucchini, bitter melons, etc. are easily affected by cold damage below 7 °C, and their cold damage symptoms are manifested as boiled surfaces, soft rotten tissues, bitter edible parts or rapidly reduced flavor, losing their edible value, so for those vegetables that are easily affected by low temperature and cold damage, you can take batches or postpone the purchase time, pack while packing, or take individual storage and other insulation measures to prevent cold damage. Although many vegetables are sensitive to low temperatures, because the clean vegetables are extremely perishable and deteriorated and the storage period is short, the problem of cold damage of products can be ignored in actual operation when the production volume is small and the goods can be sold in time.
Precautions should be taken when using cold storage for freshness
1 temperature
Using cold storage fresh technology, controlling the temperature in the cold storage is the key. As a short-term storage of clean vegetable products, the temperature in the general cold storage should be controlled at 2~4 °C, for vegetables susceptible to cold damage (such as cucumbers, zucchini, bitter melons, etc.) can be placed in 5~7 °C cold storage, or take insulation measures such as covering quilts to prevent vegetables from being frozen. Vegetables that are easy to age, such as garlic and broccoli, should be placed in a warehouse at about 0 °C. In order to ensure the quality of finished dishes, avoid severe temperature changes and enhanced respiratory metabolism, vegetable trimming and mulching should also be carried out under the condition of 2~5 °C.
2. Humidity
In order to ensure the freshness of vegetables and reduce water loss and wilting, the humidity during storage and processing is generally controlled at 80%~95%. And during storage, according to the amount of storage and the temperature of the warehouse, pay attention to ventilation at any time.
3. Dry properly
Shiitake mushrooms, onions, ginger and other varieties with large surface water content must be properly dried before storage to reduce the moisture covering the surface of vegetables and extend the storage period.
4. Prevent stacking
Incoming vegetables should be neatly placed on the shelves, or stacked and placed in the warehouse to prevent mechanical damage to vegetables caused by excessive stacking pressure or heating in the stack, resulting in a decrease in the quality of vegetables.
