Comparison of different extraction methods effect on antioxidant properties of loquat fruit (Eriobotrya japonica Lindl.) pulp extracts in stabilization of soybean oil

In this study, the effect of maceration extraction method with three solvents (ethanol, water and ethanol/water (1:1)) on the extraction yield, total phenols and antioxidant properties of loquat (Eriobotrya
japonica) fruit pulp extracts was compared with ultrasound-assisted extraction method. The antioxidant activity of loquat fruit pulp extracts at different concentrations were evaluated and compared to tertiary butyl hydroquinone (TBHQ) using 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and β-carotene bleaching assays. Ethanol and ethanol/water extracts of maceration method had the highest extraction yield of phenolic compounds and anti-radical activities. In order to assess the antioxidant activity of extracts in oil, six types of soybean oil blends were prepared including the soybean oil with 400 and 1000 ppm of maceration ethanol extract (MEE), soybean oil with 400 and 1000 ppm of ultrasonic ethanol extract (UEE), soybean oil with 100 ppm of TBHQ and soybean oil without antioxidant (SBO). Then, the effects of extracts on oxidation of oil samples were evaluated and compared to TBHQ by using peroxide value, thiobarbituric acid value, conjugated dienes, total polar compounds, carbonyl value and acid value during 60 days of storage at 25 °C and 24 h of heating at 180 °C. Results indicated that ethanolic extract of maceration at 1000 ppm had the highest antioxidant activity compared to other extracts, but its effect was lower than THBQ.