How to identify canned sardines

The identification before opening the can is mainly based on four aspects: looking at the appearance of the container, squeezing and pressing the lid, knocking and listening, and checking for air leakage. Specifically:
First, the identification method is by sight. Mainly check whether the seal of the can is tight, whether the surface is clean, and whether there is any wear and corrosion, such as dirty, darkened, spotted, rusted edges, etc. For glass bottles and cans, you can place them in a bright place to directly observe the internal quality. After gently shaking, you can see whether the contents are neatly shaped, whether the soup is turbid, and whether there are impurities and foreign matter.
Second, hand pinch identification method. Mainly check whether there is any fat in the canned food. You can use your fingers to press the bottom and lid of tinplate cans or the lid of glass bottle cans, and carefully observe whether there is any expansion of the can.
Third, knock and listen identification method. It is mainly used to check the quality of the contents of the can. You can use a small wooden stick or your fingers to tap the center of the bottom cover of the can and listen to the sound to identify the quality of the can. The sound of good-quality cans is clear and solid, while the sound of inferior and inferior cans includes insufficient content, large gaps, and a hollow sound, which is a hoarse sound of "breaking".
Fourth, air leakage identification method. Whether the can is leaking is very important for the preservation of the can. When checking for air leakage, you usually sink the can into water and squeeze the bottom with your hands. If there is air leakage, small bubbles will be found. However, when inspecting, do not move the can when it is submerged in water, so that the small bubbles cannot be seen clearly.