The edible oil identification method is as follows:

(1) Vegetable oil-incorporated mineral oil. One ml of the oil sample was placed in a 125 ml erlenmeyer flask, 1 ml of aqueous potassium hydroxide solution (3:2) and 20 ml of absolute ethanol were added and the mixture was saponified on a water bath for 5 minutes under reflux. Saponification should be shaken. Remove the flask, add 25 ml of water and shake. If it appears turbid or has an oily substance precipitated, it indicates the presence of mineral oil.

(2) Incorporation of vegetable oil with tung oil. Take 5-10 drops of oil sample, add about l-2 ml of petroleum ether, dissolve into a clear solution in a small test tube (filter when necessary), add a little sodium nitrite crystal and 10 equivalents of sulfuric acid to about 0.5 ml, shake vigorously Let it stand and observe the light. If it is pure vegetable oil (peanut oil, soybean oil, rapeseed oil, sesame oil or tea oil) red-brown nitrogen oxide gas is produced and the oil is still clear. If it is mixed with 1% of tung oil, the oil appears white turbid; when mixed with 2.5% of tung oil, white floc appears; when tung oil is added more than 5%, white floc-like lumps condense. It is white at the beginning and turns yellow after being placed.

(3) Edible oil is mixed with castor oil. Take a few drops of oil to be tested on the white porcelain reaction plate, and then drop in a few drops of nitric acid. If it is brown, suspicious adulterated castor oil is suspected. It must be sent to the health and epidemic prevention department in time for inspection.

(4) adulterated sesame oil (fragrance).

Fragrant oil adulteration can be identified by the following methods:

Color discrimination: Pure sesame oil is light red or orange-red. Machine pressed sesame oil is lighter than small sesame oil. The color of sesame oil mixed with rapeseed oil is dark yellow, and when mixed with cottonseed oil, the color is dark red.

Smell: Small sesame oil is mellow, rich, and unique. If it is mixed with peanut oil, soybean oil, and rapeseed oil, it will not only have bad aromas, but also peanuts, soybean meal or other odors.

Observe: See pure sesame oil in the summer sunshine, it is clear and transparent. If mixed with 1.5% of cold water, it will show opaque liquid under light; if mixed with 3.5% of cold water, sesame oil will be stratified and easy to precipitate and deteriorate; if it is mixed with lard, it will turn white when heated; When rapeseed oil is heated, the color becomes blue; when it is mixed with cottonseed oil, it will stick when heated; if it is mixed with rice soup or melon soup, it will make hair when heated and will precipitate after half an hour.

Water test: Using a pair of sesame oil with a pair of chopsticks, dripping onto a calm, cool surface, the pure sesame oil will appear as a colorless, transparent and thin oil, and then condense into a number of tiny oil beads. Adulterated scented oils are small and thick and do not spread easily.

I hope that the above few small methods can help you identify the quality of edible oils and eat them safely.

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