Amino acid contents and biological value of protein in various amaranth species

Amino acid content before and after heat treatment was assessed in grain of six selected amaranth varieties and four species: Amaranthus cruentus, A. hypochondriacus, A. caudatus and A. hybridus, cultivated in the Czech Republic. High content of Lys and Arg was detected in both heat treated and untreated grains, as well as satisfactory content of Cys and lower levels of Met, Val, Ile and Leu. The latter three amino acids appear as limiting. Chemical scores of essential amino acids and essential amino acid index (EAAI) were determined. EAAI value of 90.4% shows the favourable nutritional quality of amaranth protein, which is almost comparable with egg protein. Heat treatment by popping at 170 to 190°C for 30 s resulted in decreased EAAI to 85.4%. Of the essential amino acids under study, Val and Leu contents decreased significantly (P < 0.05). The relatively high content of essential amino acids in amaranth grain predetermines its use as a substitution of meat-and-bone meals.