Abstract:Black rice anthocyanin has good antioxidant activity, but its high water solubility limits its application in oil system. In order to improve the anti-oxidation performance of ordinary black rice anthocyanins, immobilized phosphotungsten heteropoly acid based on SBA-15 was prepared. The immobilized phosphotungsten heteropoly acid was used as catalyst in the esterification of black rice anthocyanins to obtain oil-soluble black rice anthocyanins. In this paper, X-ray diffraction and transmission electron microscopy were used to verify that phosphotungstic heteropoly acid could be successfully immobilized in SBA-15 channel. The esterification rate was taken as the inspection index, the relationship between the ratio of black rice anthocyanin to acetic anhydride, the amount of heteropoly acid catalyst, the temperature and time of esterification were studied. At the same time, the molecular structure of anthocyanins from black rice was preliminarily characterized analysis and the antioxidant properties of oils were discussed. The results showed that under the conditions of 1 ∶ 2 reactant ratio, 2.5% catalyst dosage, 95.0 ℃ reaction temperature and 4.5 h reaction time, the esterification rate was about 93% and the recovery rate was over 80%. After esterification, the liposolubility of black rice anthocyanins was significantly improved, and the characteristic absorption peaks of C=O bond and ester group appeared. This indicated that the addition of new ester functional groups improved the lipophilicity of black rice anthocyanins, thus significantly improving the anti-lipid oxidation effect of black rice anthocyanins. The long-term antioxidant activity of oil-soluble black rice anthocyanins in primary soybean oil was preliminarily studied. The results showed that the antioxidant activity of oil-soluble black rice anthocyanins was higher than that of ordinary black rice anthocyanins and VE, and lower than TBHQ at the same addition amount.