Improving oxidative stability of soyabean oil by apple pomace extract during deep frying of french fries

Abstract

Repetitive use of same oil for deep-frying over extended period results in the production of various harmful compounds thus posing a serious health threat to consumers. Apple pomace, a by-product of apple processing industry is considered a rich source of various bioactive compounds, thus would be of great interest to the frying industry. The aim of this study was to explore the effect of apple pomace extract (APE) on the oxidative stability of soyabean oil during deep frying of french fries and compare it with its highest polyphenolic fraction quercetin (QE) and synthetic antioxidant tertiary butyl hydroquinone (TBHQ). Total phenols (TP) and Total flavonoid content (TFC) of APE obtained from ultrasound assisted extraction (UAE) was found to be (5.58 ± 0.27 mg GAE/g) and (5.42 ± 0.45 mg QE/g) respectively with an antioxidant activity of 76% and (9.9 mM As acid/mg) as determined by DPPH and FRAP assay. Soyabean oil enriched with natural antioxidants show higher thermal stability and quality in terms of various physico-chemical indices and sensory evaluation as compared to control and TBHQ enriched oils. Transfatty acids (TFA) in both control and antioxidant enriched oils during frying were found in higher concentration crossing the legal limit of 2%. The thermal stability of oils conferred by antioxidants follows this order QE ˃APE ˃TBHQ ˃ Control. Thus, natural antioxidants obtained from agro-industrial waste have the great potential to replace synthetic antioxidants effectively in conferring stability to deep-fried oils.