Cooling of canned fruits and vegetables: during normal pressure sterilization of fruits and vegetables, the iron cans can be directly cooled by cold water, and the glass cans need to be cooled in sections; for high-pressure sterilization, the cans can be directly cooled, and the glass cans cannot be directly contacted with cold water in the early stage of cooling (segmented cooling); The cooling water should meet the sanitary requirements of drinking water; it should be sufficiently cold (cold to 38-40℃); wipe the tank immediately after cooling
Utensils for lye peeling: Fruit and vegetable processing must use acid and alkali resistant enamel or stainless steel containers, avoid using iron and aluminum products; maintain the concentration of lye; maintain the temperature of lye; rinse immediately with water after peeling, or use 0.25-0.5 % Citric acid neutralizes.
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 designated foods; food is invalid after spoilage and deterioration; some preservatives have peculiar smells and cannot affect the original food after adding Preservatives should 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 antimicrobial spectrum of preservatives for mixed use.
Pay attention to the temperature and time of blanching: the blanching temperature required for fruit and vegetable processing is not exactly the same. For example, blanching of spinach at 76.5℃ will keep the green color well, if it is blanched in boiling water, it will cause serious chlorosis; hawthorn should be at 75 Blanching below ℃, so as not to heat swelling of pectin, causing fruit cracking; pea blanching in boiling water or slightly lower temperature, depending on the variety and maturity, asparagus is generally 80 ℃ blanching. Therefore, the temperature and time of blanching should be considered comprehensively according to the type, maturity, tenderness, color and other characteristics of the specific fruit and vegetable raw materials. Generally, it is treated in boiling water or a temperature slightly lower than the boiling point for 2-10 minutes.
The requirements for the blanching liquid: the requirements for the blanching liquid of various fruit and vegetable processing raw materials are not completely the same. For white materials, such as edible fungi, asparagus, cauliflower, etc., the pH value of the blanching liquid should be adjusted with citric acid to prevent browning (The optimum pH value of phenolase is 6-7, below 6, the activity is obviously weakened, and it can be blanched at pH=3); green raw materials such as green beans, etc. require alkali to be added to the blanching liquid to make it The pH value is about 7.5-8.0 (no more than 9) to inhibit chlorophyll demagnesium