Abstract
The oxidative stability study was performed to investigate the effect of synthetic and natural antioxidants like tert-butyl hydroquinone (THBQ), butylated hydroxytoluene (BHT) and Oryzanol by direct addition to crude and refined eri silkworm oils at 70°C. Two types of silkworm oils from castor and tapioca leaf fed pupae were studied which had different polyunsaturated fatty acid (PUFA) contents. The control and antioxidants added samples were collected for every 24 hour time interval for seven days. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (PAV), total oxidation (TOTOX), thiobarbituric acid reactive substances (TBARS) and other physico chemical characteristics. PV increased from 3.42 to 17.66 and 3.98 to 19.60 meq/kg in crude castor and tapioca leaf fed silkworm oils respectively during 7 days. After addition of antioxidants PV raised from 3.42 to 9.27 and 3.98 to 10.90 in crude castor and tapioca fed silkworm oils respectively. The same trend was observed in refined oils of both varieties of silkworm oils before and after addition of antioxidants. In all the analysis it was found that oxidation was higher in refined silkworm oils compared to crude silkworm oils which could be due to presence of tocopherols and phospholipids in the crude oils. The other physico chemical properties for both the silkworm oils did not get affected significantly during the study period. The study indicates the necessity for addition of antioxidants to both the silkworm oils for protection of nutraceutical component α-linolenic acid (ALA) against lipid oxidation.
