CBSE Class 10 Answered

Temperature and light has marked effect on randcidity. When the intensity of light to which oil-bearing foods are exposed is the same, the ultraviolet, violet, and blue regions (below 4900 Ångström units) promote rancidity the most. Regions at about 5400 and above 7400 Ångström units promote rancidity the least. The yellow region around 5700 and the red region around 6600 Ångström units are less active than the blue region but nevertheless promote rancidity appreciably more than the green region.

Temperature is another factor that accelerates rancidity. Heating at 100 ^oC has marked effect than exposure to oxygen. Best temperature for preservation is 0 ^oC or lower.

There are different types of rancidity. Hydrolytic rancidity occurs when water splits fatty acid chains away from the glycerol backbone in glycerides. Oxidative rancidity occurs when the double bonds of an unsaturated fatty acid react chemically with oxygen. Microbial rancidity refers to a process in which micro-organisms such as bacteria use their enzymes, including lipases, to break down chemical structures in the fat