EVALUATION METHOD AND BREEDING OF PURPLE SWEET-POTATO YAMAGAWA-MURASAKI (IPOMOEA-BATATAS POIR) FOR RAW-MATERIAL OF FOOD COLORANTS

YAMAGAWA MURASAKI (Ipomoea batatas POIR.), a traditional variety of pu rple sweet potato cultivated in the southern Kyushu district, is riche r in anthocyanin pigments than other varieties. However, it is unsatis factory both in pigment content and crop yield for use as a starting m aterial 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 s tep of hybridization, cultivation, pigment extraction and tuber storag e. Although no new pigment peaks were seen in the new variety, a pigme nt content change was observed at every steps. In the tuber dried and deteriorated during storage purplish red pigments of long HPLC retenti on time decreased in quantity, while yellowish red pigments of short H PLC retention time increased. In assessing the characteristics of the new variety and methods of processing it, plants with minor peak patte rn changes were selectively sampled.