ANTIOXIDANT ACTIVITY OF CURCUMIN AS A NATURAL ANTIOXIDANT ON THE OXIDATIVE STABILITY OF SOYBEAN OIL UNDER THERMOXIDATION

Abstract

: The aim of the present study was to examine and compare oxidative stability of soybean oil under accelerated oxidation conditions (at 70°C for 12 days) using curcumin at different concentrations (40, 80, and 120 µg/mL) as a natural antioxidant in comparison with control (without any antioxidant) and positive control (using synthetic TBHQ-200 µg/mL). The major fatty acids in soybean oil are linoleic acid, oleic acid, palmitic acid, linolenic acid, and stearic acid. Linoleic acid recorded the highest ratio (53.3 %), followed by oleic acid (23.7 %), then palmitic acid (11.4%), while stearic acid had the lowest level (4.1%). In rancimate test, the longest induction times were determined for soybean oil supplemented with curcumin at 80 µg/mL (6.39 h), followed by soybean oil supplemented with TBHQ at 200 µg/mL (5.83 h). The results from the accelerated storage experiment indicated that curcumin (40, 80, and 120 µg/mL) exhibited stronger antioxidant capability in all tested samples rather than control (without antioxidants). Under accelerated oxidation conditions, curcumin has a potential capability to improve the shelf life of soybean oil in comparison with TBHQ-200 µg/mL. It can be concluded that soybean oil supplemented with curcumin and TBHQ showed low peroxide value, conjugated diene, and conjugated triene content compared to control (without antioxidant). This indicated that curcumin at different concentrations (40, 80, and 120 µg/mL) has a good antioxidant activity. So, it replaces TBHQ in different applications.