Nutritional assessment of protein from beans (Phaseolus vulgaris L) processed at different pH values,in growing rats

The effect of the commonly used processing techniques of soaking (at different pH values) and cooking on the digestive and metabolic utilisation of protein from common beans (Phaseolus vulgaris L) in growing rats was studied. Before the cooking step, beans were soaked in solutions of pH 2.6, 5.3 or 8.4. Analyses of beans soaked at moderately acid pH (5.3) showed a significant increase in essential amino acids, especially cysteine. Food intake and growth indices were also dependent on pH. All indices were better in animals fed with beans soaked in a basic pH solution than when an acid soaking solution was used. In contrast with the findings expected on the basis of the chemical analysis of protein composition of the food, the worst results for food intake and growth were found in rats fed with beans soaked at pH 5.3. There were no significant differences in apparent digestibility coefficient between different groups of animals. The highest metabolic utilisation of protein (balance) was found in animals fed with beans soaked in a basic solution; however, the values were insufficient to account for the faster rate of growth in this group. The better growth rate was probably due to the improved utilisation of carbohydrates in beans soaked in the basic pH (8.4) solution. © 2001 Society of Chemical Industry