The effect of supplementing a rice diet providing about 1.3–1.4 g protein per kg body weight with lysine, methionine, and threonine individually or together on true digestibility coefficient (DC), biological value (BV), and net protein utilization (NPU) of the proteins has been studied in girls aged 8–9 years. The retention of nitrogen on the rice diet was very low (9.5% of intake in the first series and 8.5% in the second series). The BV and NPU of the proteins of rice diet were 64.1 and 52.9 in the first series and 66.6 and 54.9 in the second series. Supplementation of the rice diet with lysine or methionine or lysine + methionine brought about a significant improvement in N retention (12.6, 12.0, 13.5% of intake) and in the BV (68.3, 66.3, 69.3) and NPU (54.8, 55.7, 55.8). When the rice diet was supplemented with lysine and threonine, a highly significant improvement in the N retention (18.9% of intake) and in the BV (77.4) and NPU (63.4) was observed. Addition of methionine to rice diet containing lysine and threonine resulted in a further improvement in N retention, BV, and NPU of the diets. The net available protein (g/kg body weight) from the different diets were as follows: rice diet, 0.71; rice diet + lysine, 0.76; rice diet + methionine, 0.74; rice diet + lysine + methionine, 0.77; rice diet + lysine + threonine, 0.85; rice diet + lysine + threonine + methionine, 0.91; and skim milk powder diet, 0.96–0.98.
The true digestibility coefficient, biological value, and net available protein of diets based on processed soya flour supplemented with dl-methionine hydroxy analogue (MHA) or dl-methionine (at a level of 1.2 g/16 g N) have been determined in children aged 8–9 years. The mean daily intake of protein by the children on the different diets was maintained at a level of about 1.2 g/kg body weight. Supplementation of soya flour with dl-methionine brought about a marked increase in the biological value and net protein utilization of the proteins. MHA was, however, slightly less effective than dl-methionine in this respect. The biological value and net protein utilization of the different proteins were as follows: soya flour, 63.5 and 53.3; soya flour + MHA, 71.5 and 61.4; soya flour + methionine, 74.9 and 64.7; and skim milk powder, 82.6 and 72.0.
The effect of supplementing a poor rice diet commonly used in India with methionine-fortified soya flour or skim milk powder was studied in seven girls aged 8–9 years, using as criteria: the retention of nitrogen, digestibility coefficient, biological value, and net protein utilization of the proteins. The retention of nitrogen on the rice diet was very low (20.3 mg/kg day). Supplementation of the rice diet with soya flour, methionine-fortified soya flour or skim milk powder, so as to provide about 1 g/kg extra protein, made up the protein deficiency in the rice diet and resulted in a significant increase in nitrogen retention (95.6, 112.1, and 113.6 mg/kg day). The retention of nitrogen on the rice diet supplemented with methionine-fortified soya flour (112.1 mg/kg day) or skim milk powder (113.6 mg/kg day) was nearly the same and significantly higher than that (95.6 mg/kg day) observed with a diet supplemented with soya flour. The biological value and net protein utilization of the mixed proteins of rice – skim milk powder diet and rice–methionine-fortified soya flour diet (62.4 and 62.2 and 53.3 and 54.0 respectively) were nearly the same and significantly higher than those (58.3 and 49.9) of rice – soya flour diet. The results show that methionine-fortified soya flour is almost as good as skim milk powder and significantly superior to soya flour as a protein supplement to rice diet.
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