First, seeing the identification method. The main check can seal is tight, the appearance is clean, there is no wear and corrosion situation, such as appearance of pollution, darkening, starting spots, edge rust and so on. If the jar can be placed in a bright place directly observe the internal quality of the situation, gently shaking after the contents of the object is neat, whether the soup is cloudy, there are no impurities foreign bodies.
Second, the hand pinch identification method. The main check can have no fat hearing phenomenon. Can be used to press the bottom and lid of tin cans, glass cans can be pressed bottle cap, carefully observe the phenomenon of bulging cans.
Third, the authentication method of knocking. Mainly used to check the quality of canned goods, can be used as small sticks or fingers percussion can at the bottom of the center, listen to the sound of the quality of the identification can. The sound of the good can is crisp, the voice is sound, the inferior quality and the low quality can include the content is insufficient, the sound of the Void is big, the empty sound, namely "broken" hoarse sound.
IV. Leak identification method. Whether the cans are leaking is very important for the preservation of canned goods. When conducting a leak check, it is usually to sink the can into the water with the hand to squeeze the bottom, if there is a leak in the place will find small bubbles. But when the check can be submerged in water do not move, lest small bubbles can not see clearly.