In the market to buy canned, to determine its quality is good or bad, usually can be identified using the following methods.
(1) tapping test: with the middle finger gently tapping the lid and the tin bottom of the tin, listen to the sound to identify. If the issue of "bang" drum sound, and more are biological or chemical fat listen, if issued a real sound, it is physical fat to listen to.
(2) Press test, with the fingers pressed can lid or the bottom of the tin, biological and chemical fat cans, not easy to press down, or press down to let go after the bulge, physical fat listen, easy to finger Press, release the finger will not restore the status quo.
(3) water test: the fat cans to tear on the labels, scrub clean, on 85 ℃ or so in the water, the water above the canned 3 to 5 cm, after 5 minutes, if the canned parts of a continuous Bubble to escape, there is no smell of corruption, are mostly chemical fat listen, if there is corruption of the smell, it is biological fat to listen to, no gas escape, it is physical fat to listen.