Oxidative Stability of Refined Soybean Oil Enriched with Loquat Fruit (E riobotrya japonica Lindl.) Skin and Pulp Extracts

Abstract

The aim of this study was to compare the effects of loquat fruit (Eriobotrya japonica Lindl.) skin and pulp extracts on stabilization of soybean oil during heating process. The antioxidant capacities of the extracts were determined using DPPH (2,2-diphenyl-1-picrylhydrazyl) and β-carotene–linoleic acid methods. The results showed that ethanol–water extract of skin (at 400 and 1,000 mg/kg) and ethanol extract of pulp (at 100 and 400 mg/kg) had the highest antioxidant activity. Moreover, the antioxidant potency of skin was more than that of pulp, which was due to the large tocopherol and phenolic contents. Oxidative alterations were measured by total polar compounds, carbonyl value, oxidative stability index, free fatty acids, and conjugated dienes and trienes values. Our results also confirmed that the protection offered by 400 mg/kg of ethanol–water extract of skin (SSA) is comparable with, or in some cases better than, that of tertiary butylhydroquinone (TBHQ). Practical Applications The oils and fats that are prone to oxidation can be stabilized with the help of natural antioxidants. The antioxidant effects of these natural extracts are due to the presence of bioactive compounds in the extracts. This study reveals that the natural extracts showed antioxidant activity equal to that of synthetic antioxidants like tertiary butylhydroquinone. Therefore, loquat skin and pulp extracts can be used to replace synthetic antioxidants used in vegetable oils.