ANTIOXIDANT EFFICACY OF MANGO AND JACKFRUIT SEED EXTRACTS ON OXIDATIVE STABILITY OF PALM OIL ON DEEP FRYING

Abstract

The effects of antioxidants on the changes in quality characteristics of refined, bleached, and deodorized (RBD) palm oil during deep-fat frying (at 180°C) of potato chips for seven consecutive days in five systems were compared in this study. The systems were RBD palm oil without antioxidant (control), with 200 ppm butylated hydroxytoluene (BHT), 200 ppm butylated hydroxyanisole (BHA), 200 ppm mango seed extract, and 200 ppm jackfruit seed extract. Fried oil samples were analyzed for peroxide value (PV), iodine value (IV) and free fatty acid (FFA) content. The extract were prepared by reflux using ethanol solvent in the ratio of sample/ethanol of 1:3 (w/v) and then by vacuum evaporation at 40°C. The yield, flavonoid content, phenol content and DPPH radical scavenging activities of both of the extracts were determined. The average yields were found to be 11.28% and 10.37 % for MSK extract and JSK extract respectively. The total phenol content for Mango Seed Kernel (MSK) extract (117 mg Gallic acid equivalent/g) was found to be significantly higher (p ≤ 0.05) than that for Jackfruit Seed Kernel (JSK) extract (27.7 mg Gallic acid equivalent/g of the dried extract). Similarly, the total flavonoid content for MSK extract (0.372 mg Rutin equivalent/mg dry extract) was found to be significantly higher (p ≤ 0.05) than that for JSK extract (0.195 mg Rutin equivalent/mg dry extract). The lowest IC50 value of the MSK extract (0.112mg/mL) in comparison to BHA(0.2108), BHT(0.1558) and JSK(0.2884) indicated that it exhibited the highest DPPH (2, 2-Diphenyl-1-Picryl Hydrazyl) free radical scavenging effect. With respect to PV, the oxidative stability was decreased in the order MSK extract ≈ BHT>JSK extract ≈ BHA>control. Judging the FFA content of the oil at the end of frying operation, the increment of FFA content in oil system was in the order MSK extract<BHT<JSK extract ≈ BHA and the change in IV showed that the effectiveness in protecting oxidation of unsaturated fatty acid was in the order: MSK extract>BHA>JSK extract>BHT>control. Therefore, MSK extract was best among the other antioxidant used such as BHA, BHT and JSK in terms of health aspect and protection against the oxidation process of the oil. Thus, mango and jackfruit seed could be effectively utilized for the preparation of extracts which could be used instead of the synthetic antioxidants such as BHA and BHT for increasing the oxidative stability of palm oil on deep fat frying of potato chips.