Effects of common bean enrichment on nutritional quality of tortillas produced from nixtamalized regular and quality protein maize flours

In Mexico the tortilla is most commonly eaten in the form of 'taco'; this is normally accompanied with other food, in particular the common bean. Tortillas made of quality protein maize (QPM) fortified with common bean might be a strategy to improve their protein quality. In this study, amino acids and mineral changes that occur during nixtamalization and the chemical and nutritional characteristics of regular, commercial and QPM tortilla-bean combination were assessed. After nixtamalization, protein from QPM nixtamalized maize flour was reduced from 8.1% to 7.2% (w/w). Tryptophan was also reduced from 12.1 to 11.1 g kg(-1) protein. QPM maize retained a higher amount (P < 0.05)of calcium (3180 mg kg(-1)) compared to regular maize (1820 mg kg(-1)). When nixtamalized maize flour of regular maize and commercial tortilla were combined with beans, protein content increased. The tryptophan and lysine contents in these tortillas were increased (P > 0.05) also, but were significantly lower (P > 0.05) than in tortilla made with QPM maize fortified with bean (22.7 and 69.9 g kg(-1) protein, respectively). Mineral contents increased in tortilla-bean combination. The QPM and tortilla fortified with bean gave an improvement in protein quality and could contribute significantly towards human nutrition, especially in countries like Mexico where maize and beans are important components of the diet. (c) 2007 Society of Chemical Industry.