Modification of Methods for Determination of Dietary Fiber in Raw and Processed Pulses

This study was conducted to evaluate and to improve the A. O. A. C. method and modified Prosky method for determination of dietary fiber in raw and processed pulses.1. When dietary fiber in raw, home-cooked and commercially cooked white kidney beans and kintoki beans was analyzed by the A. O. A. C. method, the method overestimated the dietary fiber contents in some cooked beans compared with those in the raw beans. In the case of soybeans, however, there was practical agreement between dietary fiber values in raw and some processed beans.2. Dietary fiber values in white kidney beans and kintoki beans were affected by the conditions of boiling in water or autoclaving (time and temperature).3. After boiling in water for 30min or 60min, dietary fiber values increased 105% in kintoki beans, 77% in white kidney beans, 36% in azuki beans, 23% in blue peas, 19% in broad beans and 11% in soybeans compared with the values in the raw pulses, respectively.4. There were differences in available carbohydrate, protein and lipid contents between soybeans and other pulses. Dietary fiber values might be overestimated in pulses which contain more starch; the enhanced dietary fiber content might reflect a retrograded starch which can be defined as “resistant starch”.5. After solubilization with dimethylsulfoxide, samples were analyzed by the modified Prosky method. Following this treatment, dietary fiber values in the processed pulses compared satisfactorily with those in the raw pulses.