Oil rancidity refers to the fact that oil first generates hydroperoxide under the action of oxygen in the air, and the hydroperoxide further reacts to generate organic peroxide, which can cause sensory changes and reduce the nutritional value of food.
Oil rancidity is usually due to high unsaturated fatty acid content or poor storage conditions, such as high temperature and humidity, long illumination time and so on. In fact, foods with high oil content, such as milk powder, biscuits, cakes, dried salted fish, canned food, walnuts, peanuts, melon seeds, instant noodles, etc., are prone to spicy taste.
If this oily food is stored for too long, it will be oxidized and rancid under the action of sunlight, air, water and temperature, resulting in peculiar smell.
preventive measure
Keep away from light, and store the oil in a cool place. The oil container should be made of dark metal, and the storage temperature of oil should be 10~ 15℃. The common method of antioxidant is to add various antioxidants, such as chemical antioxidants and butyl hydroxyanisole, as well as various plant extracts, such as orange peel extract, soybean isoflavone, tea polyphenols and so on.
In addition, when the content of vitamin E in oil reaches 0.0 1% ~ 0.03%, it can play a good antioxidant role. Vacuum nitrogen charging can also reduce the oxygen consumption of oil, reduce the deterioration speed and extend the shelf life. Microencapsulation and powdering of oils and fats, due to the coating effect of wall materials, isolate oils and fats from air and water, thus preventing oils and fats from oxidative rancidity.
Metal passivator is used to remove trace metals. According to research, the existence of trace metals such as copper, iron and lead will have extremely adverse effects on the oxidative stability and taste of oils and fats.
This is because these trace metals can catalyze oxidation, and they are pro-oxidants. The role of the metal passivator is to complex with the pro-oxidation metal, so that the pro-oxidation metal is included in the complex structure or ring structure, so that the metal no longer plays the role of pro-oxidant.
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