INVESTIGATING CHANGES AND EFFECT OF PEROXIDE VALUES IN COOKING OILS SUBJECT TO LIGHT AND HEAT

Abstract

The quality of the oils is dependent on their chemical compositions, like the percentage of the degree of unsaturation. The peroxide value (PV), which depends on temperature, time and light, measures the extent of primary oxidation of oils (rancidification). Rancidity of oils can produce potentially toxic compounds associated with long-term health effects such as neurological disorders, heart and cancer. Oils with a high degree of unsaturation are highly susceptible to oxidation as compared to saturated oils. Moreover vegetable oils become rancid much faster than animal oils. Oils also become susceptible to microbial rancidity, in which microorganisms such as bacteria and yeast use their enzymes to break down chemical structures in the oil, leading to the production of unwanted odors and flavors. To investigate oxidative initial rancidity of oils the PV value is determined. Twenty different oils were selected and subjected to two different frying temperatures: 130⁰C and 170⁰C. This change from 130⁰C to 170⁰C using same frying time (20 minutes) was noticed to cause changes in PV of pure oil, though in many cases (except Seasons corn oil, Season canola, Kausar banaspati, Dalda Groundnut) the PV value was constant after 130 ⁰C. These results show that it is important to add antioxidants such as vitamin E or C as preservatives in vegetable oils to delay or down slow the development of rancidity.