How to identify waste oil how to identify waste oil how to identify all kinds of waste oil? Take a look: look at transparency, look at color. Dark color, turbid, with sediment. It may be waste oil that is easy to solidify at low temperature. The first detection trick is to pour a little oil on the popsicle, and the oil will soon solidify and adhere to the popsicle, probably made of waste oil. The second trick is to pour a little oil on the glass. If the oil flows slowly, there may be a problem.

Second smell: Each oil has its own unique smell. You can put a drop or two of oil on your palm, rub your hands together and smell it carefully while it is hot. It's probably that the cooking oil tastes bad and smells very weak.

The third taste: take a drop of oil with chopsticks and taste it carefully. The oil with peculiar smell may be gutter oil, the edible oil containing gutter oil is not fragrant, and the residual oil residue is black carbon.

Listen 4: Take one or two drops of oil from the bottom of the reservoir, spread it on flammable paper, ignite it and listen to its sound. If the combustion is abnormal, it will make a "squeaky" sound, indicating that the water content exceeds the standard and it is an unqualified product; When burning, there is a "crackling" explosion, which indicates that the water content of the oil is seriously exceeding the standard, and it may be doped with products, so it is absolutely impossible to buy it.

Five questions: ask the merchants about the purchase channels, ask for the purchase invoices or check the sampling report of the local food hygiene supervision department if necessary.

Physical and chemical inspection of waste oil

Moisture content, specific gravity, refractive index, saponification value, acid value, carbonyl value, peroxide value, iodine value, relative unsaturation of heavy metals, fatty acids, cholesterol, residue detection, oxidation product detection, conductivity of waste oil and so on.