1, standard test method for peroxide value.
① Saturated potassium iodide solution: Weigh 14g potassium iodide, add 10ml water to dissolve it, accelerate the dissolution with slight heat if necessary, and store it in a brown bottle after cooling.
② Chloroform-glacial acetic acid mixed solution: measure 40ml of chloroform, add 60ml of glacial acetic acid and mix well.
③ 0.02mol/L sodium thiosulfate standard solution: weigh 5g sodium thiosulfate (Na2S2O3 5h2o) (or 3g anhydrous sodium thiosulfate), dissolve it in 1000ml water, slowly boil it for 10 min, and cool it. Leave it for two weeks and filter for later use.
④ 10g/L starch indicator: weigh 0.50g soluble starch, add a little water to make it into paste, pour it into 50ml boiling water, mix well, boil and prepare immediately.
2. Peroxide value is an index indicating the oxidation degree of oils and fatty acids, which is used to explain whether the product is deteriorated due to oxidation. Eating foods with excessive peroxide value may cause diarrhea and damage the liver.
3. After the oil is oxidized, peroxides, aldehydes and ketones are generated. Strong oxidizing ability, which can oxidize potassium iodide into free iodine. Sodium thiosulfate can be used for titration. The peroxide value is a measure of oleic acid spoilage. Generally speaking, the higher the peroxide value, the more rancid it is! Because some small molecular substances produced by oxidative rancidity of oil have adverse effects on human body, such as free radicals, oil with too high peroxide value is not good for health.
4. Detection significance: the peroxide value can reflect the quality of food to a certain extent. In addition to the quality inspection of edible oil, when there is grease in processed food raw materials, it is generally necessary to detect the peroxide value, such as cakes, moon cakes, instant noodles, mung bean cakes, peach cakes, lotus seed cakes, biscuits, bread, shaqima, meat products, nuts, aquatic products and their products, and quick-frozen dumplings.
Brief introduction of peroxide value:
The peroxide value is an index indicating the degree of oxidation of oils and fatty acids. It is the content of active oxygen in 1 kg sample, expressed in millimoles of peroxide. Used to indicate whether the sample has deteriorated due to oxidation. Those foods made of fat.
Oil oxidation produces peroxides, aldehydes, ketones, etc. Strong oxidizing ability, which can oxidize potassium iodide into free iodine. Sodium thiosulfate can be used for titration. The peroxide value is a measure of oleic acid spoilage. Generally speaking, the higher the peroxide value, the more rancid it is!
Because some small molecular substances produced by oxidative rancidity of oil have adverse effects on human body, such as free radicals, oil with too high peroxide value is not good for health.