Antioxidative activity and food chemical properties of anthocyanins from the colored tuber flesh of potatoes

Abstract

This study was pursued to elucidate the food chemical properties of anthocyanins in the colored tuber flesh of 5 varieties. Freeze-dried anthocyanins were prepared and dissolved into a buffer solution by the following procedures. Anthocyanins were extracted from the sliced tubers with methanol containing 1% TFA. After removal of lipid, the crude liquid was washed and purified by a Diaion HP-20 resin. The anthocyanin fraction was eluted from the resin by adding methanol to the column, followed by condensation and lyophilization. Heat treatment faded the anthocyanin color and its degree was more intense in purple pigmented varieties than in red ones. Radiation of light also weakened the pigment intensity, and its effect was slightly mild to purple colored varieties compared to red ones. Addition of ferrous ion decomposed the anthocyanin pigments, but its effect differed among the varieties tested. Influence of pH on the color depended on the acidity in a buffer solution, namely, the lower pH, the more intensity. Antioxidative activity was assayed by a ferric thiocyanate method. The extract of anthocyanins showed more effective antioxidative activity than that of a-tocopherol against the oxidation of linoleic acid in a potassium phosphate buffer (pH 7.0), and exhibited a strong activity as the same as BHA and BHT.