PP45 - Microwave versus electrical oven heating influence on oxidative stress parameters, flavonoids and polyphenols content of five different commercial cooking oils

Abstract

Consumers are increasingly concerned about the health aspects of food preparation. There is data to support that foods treated with microwaves (MW) develop harmful substances. Vegetable oils are susceptible to lipid peroxidation due to the chemical structure, but also contain antioxidant compounds. Peroxidation products can have harmful effects for human health. The aim of the study was to evaluate the variation of total antioxidant capacity and antioxidant degradation in relation to lipid peroxides formation during conventional and microwave oils heating. Sunflower, corn, soybean, palm and a mixed oil (sunflower, grape, flaxseed and rice oil) were purchased from the local market. To simulate home cooking, different exposure times were tested 5, 10 and 15 min. For all samples, and for each exposure time, Trolox Equivalent Antioxidant Capacity (TEAC), lipid peroxides as thiobarbituric reactive substances (TBARS), conjugated dienes, vitamin E as α-tocopherol, flavonoids and total polyphenols were determined. After 15 minutes heating the best retention for vitamin E was observed for the palm oil (MW 12 mM/l), and corn oil (convection 17 mM/l). The highest total antioxidant capacity after heating belonged to mixed & palm oil (MW 4.6 eq. TROLOX/l) and soybean oil (convection 7.5 mM eq. TROLOX/l). Highest levels of TBARS belonged to the mixed oil (convection 54 uM/l) and soybean oils (MW 83 uM/l). Highest conjugated dienes levels were observed for soybean oil (MW 17 mM/l) and sunflower oil (convection 22 mM/l). The best retention for polyphenols was found in the mixed and sunflower oils (MW and convection 0.80.9 mg/ml. The retention of flavonoid was very small in all oils and the highest amount was found in corn and soybean oil (0.04 mg/ml). During the heating of edible vegetable oils commonly used, total antioxidant capacity along with the amount of vitamin E, flavonoids and polyphenols decreases, while the amount of lipid peroxidation products increases and these processes are more intense when using microwave heating than when using convection heating.