Nutritional characterization of quality protein maize (QPM) (Zea mays L.) protein concentrates

Abstract

Maize is considered a staple food for the population; however, its protein contribution to the development of individuals is limited by its low quality. Quality protein maize varieties (QPM) have been developed to remedy this. The protein quality presents in protein concentrates obtained from two QPM varieties was evaluated: Sac Beh (SB) and Chichen Itza (ChI), which were compared with a traditional variety (Blanco Uxmal, BU) as a control. All were evaluated with non-nixtamalization (NN) and nixtamalization (N). Amino acid profile, in vitro digestibility, calculated protein digestibility-corrected amino acid score (PDCAAS), calculated protein efficiency ratio (c-PER), and biological value (BV) were determined. The extraction process of the QPM concentrates and nixtamalization had important effects on the essential amino acids Lys and Trp. In vitro digestibility showed significant differences (p < 0.05). The predominant limiting amino acid was tryptophan. The QPMs were closer to the requirements of the FAO/WHO standard, since they obtained chemical score values higher than 100% for His and Leu. PDCAAS values decreased in the amino acid tryptophan of SB and BU nixtamalized maize compared with the NN. PER7 and PER10 values were statistically higher (p < 0.05) in the QPMs compared to the BU control. The estimated biological value showed an imbalance in the concentration of essential amino acids. Lys and Trp in the QPM varieties were not sufficient evidence of increased biological value the proteins, due to the effect of the extraction processes and the alkaline heat treatment to which the maize grains were subjected.