The quality of the sealant at the crimping part should be excellent, and the position and thickness of the glue injection should meet the standard requirements accurately. The whole process of can making should be very careful to avoid scratches and scratches on the plate. Even slight bruises should be removed to ensure that the canned food meets the sealing requirements. The principle of food can preservation is to rely on the container to be sealed, moderately sterilized, no preservatives are required or allowed to be added, and the finished product reaches commercial sterility and can be stored for a long time at room temperature. Therefore, canned food has very strict requirements on container tightness.
The container is an inseparable and important part of canned food. It should be absolutely sealed. The air and microorganisms outside the can cannot penetrate into the can to ensure that the canned food will not be contaminated again. The raw and auxiliary materials used in the food can should be fresh and thoroughly Clean up. Special attention must be paid to shorten the processing time of semi-finished products as much as possible. The time from pre-cooking of raw materials to sterilization should not exceed 2.5h, and the time from canning to sterilization should not exceed 30min. During this time, bacteria can multiply in large numbers, and the number of bacteria can increase from dozens to hundreds of times. The more bacteria there are, the longer the sterilization time is at the same temperature; the more bacteria spores, the higher the temperature required for sterilization and the longer the sterilization time. Taking Clostridium botulinum No. 97 as an example, the time to kill all spores per milliliter at 100℃ is compared as follows: The number of spores per milliliter is 72×109230～240min 65×10480～85min32835～ The raw materials are not fresh for 40 minutes, the temperature is high, and the processing time of semi-finished products is too long, which can easily cause the canned food to deteriorate before sterilization. A certain factory produces boneless canned chicken. The processing time of semi-finished products is too long, with an interval of 145 minutes, and then sterilization.
Bacteria increased to 520 times, and Escherichia coli increased to 1,600 times. As far as canned meat is concerned, the longer the waiting time for sterilization of the semi-finished products after the canning, the higher the temperature, and the spoilage bacteria in the cans, such as aerogenes or welchella bacteria, multiply very quickly, although they have been killed by sterilization , But the cans appear low vacuum or light swelling. After opening the cans, no live bacteria can be detected after inoculation and culture. A large number of dead bacteria can only be observed under a microscope. The maximum filling volume and initial sterilization temperature of canned food should be checked regularly at the beginning of sterilization. The maximum canning volume of solids set by the original process regulations. If the volume of cans exceeds a lot in actual operation, the original sterilization regulations are still used, and incomplete sterilization may occur. Physical swelling may also occur due to excessive solids. It is very important to regularly measure the initial temperature of sterilization. The initial temperature set by the sterilization procedures, if the initial temperature is relatively low in actual production, will cause incomplete killing and corruption and expansion. The initial temperature of canned sweet corn is 71.1℃. It takes 40 minutes for the center temperature of the can to reach 115℃. The initial temperature of 21.1℃ takes 80min for the center temperature of the can to reach 115℃. (3) Canning equipment and tools The production equipment and tools of the canning workshop are in each shift It should be cleaned and disinfected immediately at the end of production, and it should be cleaned before the next shift before production. All equipment must be able to be loaded and unloaded in situ for easy cleaning and disinfection. The welding seams of equipment and containers should be smooth and smooth to avoid breeding bacteria.