GENETIC-VARIATION IN COLOR OF SWEET-POTATO FLOUR RELATED TO ITS USE IN WHEAT-BASED COMPOSITE FLOUR PRODUCTS

Sweetpotato flours vary widely in color depending on genotype, and whe n used in wheat-based composite flours, they will impart characteristi c colors which may be favorable or unfavorable for particular food pro ducts. Sweetpotato flour (SPF) was prepared from 44 genotypes and anal yzed for proximate composition and biochemical properties. The Hunter Color L, a*, b* values of the dry SPF and their modified Pekar slicks (PS) with water and with alkali were measured. Polyphenol oxidase act ivity, alpha-amylase activity, and total sugar were significantly corr elated to L values of dry SPF and of their PS tests with water and wi th alkali. The yellow pigment level was significantly correlated to th e yellowness (b) of the dry flour and of the PS test with water, but less correlated (b) of the PS test with alkaline. The results indicat ed a complex biochemical basis to SPF color, and no single biochemical factor examined was adequate to predict the color of a food product m ade from SPE However, the PS color parameters were highly correlated w ith the color of dough sheets for white-salted and yellow-alkaline noo dles made from wheat and sweetpotato composite flour (75:25). Thus, th e simple modified PS test could be used in screening of genotypes for color stability and suitability for a specific end-use. SPF genotypes conferred a wide range of colors on composite flour dough preparations . Some colors, particularly the range of greens and bright orange, may be useful in specialty product development.