Antioxidant properties of genistein in a model edible oil system

Antioxidant properties of genistein were tested during the low temperature oxidation of linseed oil. Four linseed oil solutions were prepared: linseed oil, linseed oil containing 2 mu mol added genistein/g oil, linseed, oil containing 4 mu mol added genistein/g oil, and linseed oil containing 200 ppm butylated hydroxyanisole (BHA). Dimethyl sulfoxide (DMSO) (1.7%) was added to all solutions to allow for the solubilization of genistein. Antioxidant activities were analyzed using 2 techniques: (i) the oven stability test carried out at 60 degrees C with periodic determination of peroxide values (PV); and (ii) oxidation on a heated (60 degrees C) FTIR-ATR crystal with periodic scanning and collection of infrared spectra. Induction points (IP) for each solution were determined. A strong correlation (r = 0.91) was noted between the 2 analytical methods used. Three significantly (P < 0.10) different levels of IP were generally observed. The shortest IP (17 h for PV, 36.9 h for FTIR) was found for the linseed oil. Intermediate IP's were obtained for the 2 mu mol added genistein/g oil (32.4 h for PV, 43.5 h for FTIR) and 4 mu mol added genistein/g oil (33.9 h for PV, 44.2 h for FTIR) samples. The longest IP (39.9 h for PV, 54.2 h for FTIR) was obtained for the 200 ppm BHA containing solution. Although genestein was not as effective as BHT in retarding oxidation, the results clearly demonstrate, that it is able to act as an antioxidant in a bulk oil system.