Inhibition of soybean oil oxidation by extracts of dry beans (Phaseolus vulgaris)

Polyphenolic compounds were extracted from pinto, kidney, white (Great Northern), pink, and black beans by hot methanol extraction and added to soybean oil. Oil oxidation was assayed by thiobarbituric acid-reactive substances (TBARS). All bean polyphenolics extracts exhibited similar antioxidant capacity in delaying the onset of iron-catalyzed oxidation better than butylated hydroxyanisole (BHA), propyl gallate (PC), and ascorbic acid. Bean polyphenolic compounds were stable after heating to 50 degrees C and maintained their antioxidant potential after 3 mon at 4 degrees C. Bean extracts effectively inhibited iron-catalyzed oxidation of soybean oil, probably by chelating metal ions, because no antioxidant effect was observed when soybean oil was oxidized without an iron catalyst.