Culinary practices and consumption characteristics of common beans at the rural home level.

A survey was carried out on housewives of rural bean-producing areas for the purpose of collecting information on bean selection procedures, culinary practices and bean consumption in rural homes from four departments of northeastern Guatemala. The study sample consisted of 10 families selected at random from each of 19 municipalities. The questionnaire used had been pretested in two rural communities not included in the study sample. As already shown by other INCAP surveys of this nature, it was found that all families consumed common black beans, and on rare occasions beans of different color or species. With respect to cooking practices, it was found that beans are not usually soaked prior to cooking, and that few housewives add salt at the beginning of cooking. Two fractions are usually obtained, the cooked beans and the cooking broth. Another finding was that beans are consumed in four preparations: cooked whole, strained and fried, ground and fried, and cooked and fried. Bean broth is consumed by both adults and children, and a thick broth is preferred since it is considered to be more nutritious and better tasting. Children begin to consume bean broth as early as two months of age, and beans at 14 months. The average amount of broth ingested was 62 g, and whole cooked beans, 70 g. Mothers surveyed indicated that broth was administered to children because: it was nutritious (56% of the mothers); in order to teach children how to eat (15%); or because of its taste (9%). Regarding the hard-to-cook phenomenon, 32% of the housewives indicated that storage time was responsible for it, while 17% attributed this condition to bad seeds, and 18% to sun-drying or inadequate postharvest practices and to their preparation for consumption. Although the survey confirmed the importance that common beans have in rural diets, the main finding was that the first bean food product fed to children is the bean-cooking liquor or broth, which on the average contains 8.52% of total solids and 1.48% protein.

[Chemical composition and evaluation of the protein quality of beans in adult humans by the short-term nitrogen balance method]. / Composición química y evaluación de la calidad de la proteína del frijol en humanos adultos por el método de balance nitrogenado de corto tiempo]

Three varieties of common beans were chemically analyzed and their protein quality was evaluated in 12 human male adult subjects by the short-term nitrogen balance method. Chemical analyses were performed for both raw and cooked grains. Cooking reduced the trypsin inhibitors in 28 to 73%, hemagglutinins, 100%, tannins as acid tannic equivalents, 9 to 72%, and 55 to 75% as catequin equivalents, and alkali-soluble nitrogen in 65%. Red and black beans contained more residual trypsin inhibitors and tannins than white beans, while the latter contained more alkali-soluble nitrogen. Although cooked colored beans had more antinutritional factors that affect protein digestibility, their protein quality was similar to that of white beans. This could be explained by the fact that the amino acid composition and/or balance of red and black beans absorbed nitrogen is better than that of white beans, so that the final nutritional value will be determined by the sum of interactions between all factors. In this study, each of the three varieties presented at least one protein quality depressor in higher concentration than the other two varieties. Therefore, the overall differences found between treatments and residual effect, were small or non existent, while significant differences (p greater than 0.05) were found between subjects and nitrogen balance periods. A level of 0.65 g of bean protein/kg/day was not enough to maintain nitrogen balance in subjects fed a diet where beans were the only protein source. According to calculations, 0.9-1.0 g of bean protein/kg/day are necessary for nitrogen balance in male adults, and 1.2-1.3 g of protein bean would be the recommendation for a normal population.

[A new alternative for estimating recommendations of protein intake in humans. Protein requirements of an adult population fed with a diet based on rice and beans]. / Nueva alternativa para el cálculo de recomendaciones de ingesta de proteína en humanos. Necesidades de proteína de una población adulta alimentada con dietas a base de arroz y frijol.

This paper proposes a new approach to estimate the protein needs of a population; recommendations are also made on the protein intake of adults fed diets based on rice and beans. For this purpose, the nitrogen balance data previously reported for 40 adult human subjects who had participated in 160 nitrogen balance periods fed diets based on rice and beans, with and without animal protein and/or energy supplementation were used. The proposed method is based on the curvilinear response between nitrogen intake and its nitrogen balance. The second degree equation describing the relationship between nitrogen balance and intake is calculated. Using the mathematical concept of the first and second derivatives, the point of inflexion is obtained, and interpreted as that condition wherein the individual utilizes with maximum efficacy the ingested nitrogen; nitrogen ingestion, which corresponds to that point, is therefore taken as the dietary nitrogen recommendation for the individual. When the values obtained by means of the quadratic equation are compared to those obtained by the traditional linear equation, values were found to be statistically equal (p less than 0.05) for both calculation methods. The recommended protein intake of an adult population fed a diet based on rice and beans was 0.80 and 0.77 g/kg/day for the quadratic approach, and for the conventional method, respectively. When this diet was supplemented with 10% milk protein and with the same energy level, the calculated values were 0.64 and 0.71 g protein/kg/day for both methods, in this same order. The essential amino acid intake and absorption values were also calculated from the protein levels recommended by both methods to be in nitrogen balance, from a diet based on rice and beans. Findings revealed, in all cases, that the intakes of each and all essential amino acids met those levels indicated by FAO/WHO, with the exception of isoleucine and the sulphur-containing amino acids, which apparently limit the quality of the diet.

[Digestibility, protein value and protein requirements of diets based on plantain/bean and cassava/bean in young adults]. / Digestibilidad, valor proteínico y necesidades de proteína de dietas a base de plátano/frijol y de yuca/frijol en jóvenes adultos.

Information is provided on the nitrogen intake for nitrogen equilibrium in young human adults fed a cassava/bean diet and a plantain/bean diet. Ten individuals participating in each study ingested levels of 0, 0.2, 0.4 and 0.6 g protein/kg/day at a constant energy level (45 kcal/kg/day), using the short-term nitrogen balance method with multiple intakes. Even with intakes of 105.7 and 117.4 mg N/kg/day for the cassava/bean and plantain/bean diets, the experimental subjects did not reach a positive balance. The protein digestibility of the diets was low, as had been confirmed previously for beans alone: 55.7% for the cassava/bean study and 50.4% for plantains/beans. The average quantity of nitrogen intake required to reach nitrogen equilibrium for the cassava/bean diet was 114.3 mg N/kg/day and for the plantain/bean diet, 111.9 mg N/kg/day. In the case of the cassava/bean diet, the variability was 81.3 to 172.4, and for plantain/beans, 83.6 to 219.3 mg/kg/day. In four of the five individuals who participated in both studies, the nitrogen intake required to reach nitrogen equilibrium was greater when fed the diet based on plantain/beans than when fed the cassava/beans diet. These data support the assertion that the protein requirement is not a simple figure. Individual variability is so great that, as has been suggested, it is necessary to add two standard deviations to the average figure to cover 97.5% of the population. The results of this investigation support the need to increase protein digestibility and protein quality of beans, since this is a food of major importance for large population segments in the developing countries.

[Effect of animal protein supplementation and energy on the protein quality of diets based on rice and beans in adult males]. / Efecto de la suplementación de proteína animal y energia en la calidad proteínica de dietas a base de arroz y frijol en hombres adultos.

Four short nitrogen balance index studies were carried out in adult subjects to evaluate the biological quality of a mixture based on rice and beans, and also to measure the effect of animal protein and/or energy supplementation on the nutritive value of the mixture. In the first study, rice supplied 60% and beans, 40% of the protein's diet, which was administered at an energy level of 45.5 kcal/kg/day of metabolizable energy. A regression coefficient of 0.76 +/- 0.11 was found between ingested nitrogen and nitrogen balance, and a value for nitrogen maintenance of 96.2 +/- 13.7 mg/kg/day. When this same diet was administered in the second study at a 51.2 kcal/kg/day of metabolizable energy, the regression coefficient was 0.80 +/- 0.13, and that of nitrogen for maintenance, 90.1 +/- 8.7 mg/kg/day, without differences being significant (P less than 0.05) for any of the two measures. In the third study, 10% of the mixture's protein was substituted by milk protein, and given at a level of 45.2 kcal/kg/day of metabolizable energy. In this case, the regression coefficient found was 0.96 +/- 0.08, and that of nitrogen for maintenance, 78.6 +/- 10.2 mg/kg/day. These values do differ significantly (P less than 0.05) from those found in the two previous studies. When the diet of the third study was administered to the same subjects at a level of 48.9 kcal/kg/day of metabolizable energy, the regression coefficient of the equation was 0.86 +/- 0.17, and that for maintenance nitrogen, 82.4 +/- 10.2 mg/kg/day. These values are statistically equal to those found in the third study and do differ significantly from those of the first two studies. Information indicates that the supplementary effect of protein and milk occurs mainly at the digestive level. It is therefore concluded that when rice and beans are consumed jointly, in the adequate proportions, they constitute an excellent-quality food for adult humans.

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.