High-lysine Corn Fractions and Their Characteristics

GENETICISTS HAVE found opaque-2 and floury-2 mutant genes that substantially increase the total lysine and tryptophan content of com endosperm (Mertz et aI., 1964; Nelson et aI., 1965). Highlysine (opaque-2) com contains higher levels of lysine and tryptophan than ordinary com (Frost and Robinson, 1971). The good quality of high-lysine com protein has been confirmed by human feeding experiments (Bressani, 1966; Clark, 1968; Young et aI., 1971). Reportedly the nutritive value of opaque-2 corn protein is comparable to that of most proteins of animal origin. High-lysine corn offers an opportunity to improve the protein quality of diets including ordinary corn. Ordinary com contains horny endosperm, whereas high-lysine corn has none. No flaking grits were recovered from high-lysine corn in a milling study reported by Brekke (1971). High-lysine corn derived from the opaque-2 mutant strain currently produced is more floury, is softer than normal corn and has a larger germ. Possibly these differences might pose problems in adapting to some food uses. This concern prompted us to compare the characteristics of ordinary dent corn with those of high-lysine corn after dry milling. Tests included color measurements, amylograph characteristics, storage stability, extrusion cooking, fermentation and baking.