Protein Quality and Digestibility of Sorghum in Preschool Children: Balance Studies and Plasma Free Amino Acids

Abstract

The protein quality and digestibility of two high lysine (2.9-3.0 g/100 g protein) and tow conventional varieties (lysine content 2.1-2.2 g/100 g protein) of whole grain sorghum milled as flour were assessed through balance studies in 13 children 6-30 months of age. Sorghum protein provided 6.4 or 8.0% of dietary energy. Control diets contained 64% kcal protein as casein. Children consumed 100-150 kcal/kg body weight/day. Sorghum consumption was associated with weight loss or poor weight gain. We found no difference by variety in apparent nitrogen absorption or retention. Mean absorption and retention of nitrogen (+/- SD) from 26 six-day sorghum dietary periods were 46 +/- 17% and 14 +/- 10% of intake, respectively (corresponding preceding casein control values: 81 +/- 5% and 38 +/- 3%). Stool weight and energy losses during sorghum periods averaged 2.5 to 3 times control values. Plasma amino acids were determined in eleven children after 16 days of sorghum consumption. Fasting concentration of total amino acids (TAA) was similar to values previously obtained with wheat protein at similar levels of intake. Total concentration of essential amino acids (TEAA) was low as were concentrations of lysine (Lys) and threonine (Thr). Analysis of postprandial changes of the Lys/TEAA and Thr/TEAA molar ratios confirmed that Lys was the first limiting amino acid.

Sorghum: An Underutilized Cereal Whole Grain with the Potential to Assist in the Prevention of Chronic Disease

“…Although numerous studies have been conducted with human subjects (Table 3 (19,29,35,58,67, ), the majority have addressed micronutrient metabolism (such as interactions between leucine, molybdenum, and niacin), (129) iron absorption from cereals, (35) dietary fiber effects, (140) protein digestibility (144) and oral rehydration therapies. (148) This review therefore summarizes the experimental evidence that suggests protective health effects of sorghum consumption, targeting studies that investigate effects on energy balance, glycemic control, lipids, oxidative stress and cell-mediated responses.…”

A highly digestible sorghum mutant cultivar exhibits a unique folded structure of endosperm protein bodies

“…The nutritional quality of sorghum protein is of concern because, besides being low in the essential amino acid Lys, it has lower digestibility than protein of other cereal grains. Human studies in Peru (1) showed apparent protein digestibility of cooked sorghum to be only 46%, whereas values of 81, 73, and 66% were reported for cooked wheat, maize, and rice, respectively.…”

“…Other unpublished data from our group showed that environmental conditions during the growing season also influence sorghum protein digestibility. In addition, processing methods affect digestibility, such as whether sorghum is boiled to a porridge, fermented, decorticated and extruded, or germinated (1,(4)(5)(6)(7)(8). Simple cooking of sorghum flour has an uncommon and detrimental effect of decreasing protein digestibility as demonstrated by in vitro (4,5) and in vivo (9,10) studies.…”

Mutation in the seed storage protein kafirin creates a high-value food trait in sorghum

“…However, like other cereals, sorghum has poor protein quality because of lack of essential amino acids such as lysine and tryptophan [1][2][3][4] . Compounding this problem, sorghum proteins have very poor digestibility.…”

“…Compounding this problem, sorghum proteins have very poor digestibility. These properties result in severe malnutrition when sorghum is consumed as the primary protein source 3 . The predominant seed proteins in sorghum are alcoholsoluble prolamins called kafirins.…”