Nutritional value of normal, opaque-2 and sugary-2 opaque-2 maize hybrids for infants and children. 1. Digestibility and utilization.

The opaque-2 (o2) gene increases the lysine and tryptophan contents of maize and its protein quality; the sugary-2 (su2) gene improves vitreousness and density but decreases lysine; the double-mutant surgery-2 opaque-2 (su2o2) has the improved kernel characteristics and an even higher protein quality than opaque-2. Digestibility of energy and protein, and protein quality of normal, o2 and su2o2, both as endosperm (E) and whole kernel (WK) meals, were studied in eight convalescent malnourished children, 10--25 months of age. Diets provided 100--125 kcal/kg/day, 10% fat, with all of 6.4% protein calories from one of six maize meals or casein. Endosperm meals provided 83.2, 91.2 and 82.1% of energy, WK meals 73.2, 68.6 and 67.2% of energy in respective diets. Apparent N retention from E meals was lower than from WK meals, both lower than from casein. For each type of meal (E and WK) there was strong correlation between lysine "absorbed" and N retention, but this was higher from WK at equal lysine intakes. For 50% of children to match N retention from casein, presumably equal to requirement, they would have to consume 203.9, 148 or 122.5% of energy requirement as normal, o2 or su2o2 E meals, obviously impossible. For WK meals, they would have to consume 108.2, 90.3 or 84.2% of energy as normal, o2 or su2o2.