Protein digestibility and protein quality of common beans (Phaseolus vulgaris) fed alone and with maize, in adult humans using a short-term nitrogen balance assay.
Various experiments using young human adults were carried out to measure the protein digestibility of common beans, fed alone and in different forms and fed together with maize as tortillas. In all, 36 young men were used. Common bean protein digestibility was significantly lower than that observed from meat, and similar to the digestibility of a textured vegetable protein soy protein product. It was also observed that forms of consumption may affect protein digestibility of beans. Using a short-term multiple intake protein quality assay method, it was found that feeding beans alone, N equilibrium was reached with an intake of 114 mg N/kg/day, while when fed with maize in a 87:13 ratio, N equilibrium was reached with 98 mg N/kg/day. This was attributed to both a complementary protein effect and an increase in protein digestibility.
Nutritive value of brown and black beans for infants and small children.
A precooked, instantized mixture of brown and black beans, with and without 0.3% DL-methione added, served as the only source of protein in the diets of 10 recovered malnourished infants and children 10 to 42 months of age. At 6.4 to 5.7% dietary protein calories stool wet weights were twice as high, apparent N absorption significantly lower (65.6 +/- 5.9 versus 87.5 +/- 2.3% of intake), and apparent N retention much lower (9.8 +/- 6.1 versus 34.5 +/- 10.2% of intake) than during preceding and following isocaloric and isonitrogenous casein-based diets. The addition of methionine resulted in minimal improvement in N retention and a highly suggestive increase in fasting plasma free methionine. Prolonged feeding of the methionine-enriched beans at 8.0 to 10.9% protein calories supported satisfactory growth and serum albumin levels in two of three children, not so in the smallest one, in whom repeated balance studies demonstrated no decrease over time in stool wet weight and on marginal improvement in N absorption and retention. The poor digestibility of the protein in these beans is the first-limiting factor in its utilization by infants and small children.
Effect of cooking and of amino acid supplementation on the nutritive value of black beans (Phaseolus vulgaris L.)
The leguminous seeds, particularly beans (Phaseolus vuZgal.is L.), are very important sources of protein in the diets of Latin American populations of low economic status. In Central America, beans provide from 20 to 30 % of the protein in the diet and are second only to maize as a staple food (Flores, 1961). Therefore, it is very important to the people of this area to evaluate the proteins in beans and to improve their nutritive value by correcting their amino acid deficiencies through supplementation with other foods. Previous studies (Bressani, Marcucci, Robles & Scrimshaw, 1954) dealt with the chemical composition and the content of essential amino acids of samples of leguminous seeds from several Central American countries. In another study, Bressani, Elfas & Navarrete (1961) compared the essential amino acid compositions of six samples of beans with the F A 0 protein reference pattern (FAO, 1957), and came to the conclusion that methionine is the most limiting amino acid, followed by leucine and tryptophan as the second and third. It was of interest, therefore, to find out whether the order of limiting amino acids calculated from the F A 0 protein reference pattern could be corroborated by biological trials. Further, since beans are cooked to make them palatable and to free them of toxic effects (Eheart & Sholes, 1948; Jaffk, Planchart, Phez Pumar, Torrealba & Franceschi, 1955), it was also of interest to study the effect of cooking on their nutritive value. The work described here was undertaken to determine the limiting amino acids in cooked beans and the effect of the duration of cooking on the biological value of their proteins.