Evaluation Method and Breeding of Purple Sweet Potato "YAMAGAWA MURASAKI"(Ipomoea batatas POIR.) for Raw Material of Food Colorants.

Abstract

YAMAGAWA MURASAKI (Ipomoea batatas POIR.), a traditional variety of purple sweet potato cultivated in the southern Kyushu district, is richer in anthocyanin pigments than other varieties. However, it is unsatisfactory both in pigment content and crop yield for use as a starting material for industrial production of food colorants. From this variety, we bred a new variety characterized by 4 -fold pigment content and 2-fold crop yield. In this breeding, changes in pigment composition and content, determined from HPLC peak patterns, were monitored at each step of hybridization, cultivation, pigment extraction and tuber storage. Although no new pigment peaks were seen in the new variety, a pigment content change was observed at every steps. In the tuber dried and deteriorated during storage purplish red pigments of long HPLC retention time decreased in quantity, while yellowish red pigments of short HPLC retention time increased. In assessing the characteristics of the new variety and methods of processing it, plants with minor peak pattern changes were selectively sampled