Proper cooling is crucial for maintaining the quality of canned food after sterilization. The swift temperature change caused by cooling can result in sharp corners, bursts, or collapsed cans due to pressure difference, so it is important to regulate the back pressure outside the tank precisely. Chlorinated water is preferred for cooling, and the effective chlorine residual level should fall between 1-3ppm to avoid any potential contamination. Without adhering to these measures, the cooling water may pollute the tank after sterilization, hindering the overall hygiene and quality of the canned product.