After sterilization and cooling, canned food must be inspected after heat preservation or storage to measure whether its indicators meet the standards and commodity requirements, and determine the quality and grade of finished products. There are many inspection items and methods given by can making machine manufacturer. Here are a few.

1. Appearance inspection: the key point of appearance inspection is to check the double seaming state, observe whether the double seaming is closely combined, whether there are tongue, teeth, crinkling and broken, and check whether the can body seam is normal. The size of double seaming can be measured with special calipers for cans. If there are air leakage micropores in the double seaming, which can not be seen with naked eyes, it can be checked with warm water or with pressure leak detector. The inspection of the can bottom cover mainly depends on whether it is concave inward. The normal can has a certain degree of vacuum, so the can bottom cover should be concave inward.
2. Heat preservation inspection: if there are microorganisms remaining in canned food due to insufficient sterilization or other reasons, it will grow and propagate at a suitable temperature and make canned food deteriorate. Most spoilage bacteria, except some heat-resistant bacteria, produce gas and make cans expand. According to this principle, the method of heat preservation storage is used to create the optimum temperature for the growth and reproduction of microorganisms, to place it in sufficient time for the growth and reproduction of microorganisms, and to observe whether the bottom cover of the can expands, so as to identify whether the quality of the can is reliable and whether the sterilization is sufficient. This method is called the heat preservation inspection of the can. This is a simple and reliable method for inspection of canned products. But some high acid food, if you ensure the correct operation process, ensure the production of good sanitary conditions, ensure adequate sterilization, can not be heat preservation inspection. At present, most factories have adopted the commercial aseptic sampling heat preservation under the condition that the process hygiene is guaranteed and the sterilization conditions are sufficient, but they only use the whole heat preservation inspection for individual products.

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