Protein quality evaluation of Amaranthus wholemeal flours and protein concentrates

Abstract

Based on the amino acid composition, Amaranthus seed protein is known to be of higher quality than most of the major cereal grains. However, protein quality does not solely depend on amino acid profile but also on its digestibility. In this study we determined amino acid composition and in vitro protein digestibility of wholemeal and isoelectric protein concentrates (IPC) from five Amaranthus genotypes. Factors most likely to influence protein digestibility such as heating and presence of antinutrients were studied. Heating increased protein digestibility in wholemeals but slightly decreased it in IPCs. Trypsin inhibitor level was negatively but weakly correlated to protein digestibility, and the level of polyphenolic compounds was negatively and significantly correlated to protein digestibility. A slight deficiency in leucine was noted for wholemeals and in lysine for IPCs. However, based on both in vitro digestibility and amino acid profile, Amaranthus proteins were confirmed to be of better quality than those of other cereals. © 1998 SCI.