Cooling of fruit and vegetable cans: during the normal pressure sterilization of fruit and vegetable processing, the iron cans can be directly cooled by cold water, while the glass cans need to be cooled by sections; High pressure sterilization, the iron can be directly cooled, and the glass can not be directly contacted with cold water in the early stage of cooling (sectional cooling); The cooling water shall meet the sanitary requirements for drinking water; Full cold penetration (cold to 38-40 ℃); Wipe the tank immediately after cooling.
Appliances used for alkali liquor peeling: acid and alkali resistant enamel or stainless steel containers must be used for fruit and vegetable processing, and iron and aluminum products are prohibited; Maintain the concentration of alkali liquor; Maintain the temperature of alkali liquor; Rinse immediately after peeling, or neutralize with 0.25-0.5% citric acid.
Use of preservatives: The following issues must be paid attention to in the processing of fruits and vegetables: certain preservatives must be used in certain conditions and specified foods; It is invalid to use food after spoilage; Some preservatives have peculiar smell, which can not affect the original flavor of food after being added; Preservatives shall not be used in excess; No preservative can kill all bacteria, and food spoilage is often not a certain kind of bacteria, so it is necessary to study the bacteriostatic spectrum of preservatives for mixed use.
Temperature and time for blanching: the blanching temperature required for fruit and vegetable processing is not exactly the same. For example, blanching of spinach at 76.5 ℃ can keep the green color well. If blanching in boiling water, it will cause serious green loss; Hawthorn should be blanched below 75 ℃ to prevent pectin from swelling and causing cracking; Peas are blanched in boiling water or at a temperature slightly lower than the boiling water, depending on the variety and maturity. Asparagus is usually blanched at 80 ℃. Therefore, the temperature and time of blanching should be selected according to the type, maturity, tenderness, color and other characteristics of the specific fruit and vegetable raw materials. Generally, the blanching should be conducted for 2-10min in boiling water or at a temperature slightly lower than the boiling point.
Requirements for blanching solution; For green raw materials such as green concanavalin, it is required to add alkali in the blanching solution to make its pH value about 7.5-8.0 (no more than 9) to inhibit the removal of magnesium from chlorophyll.
