Changes in the carbohydrate composition of legumes after soaking and cooking

Using a high-performance liquid chromatography (HPLC) method, researchers analyzed the sugar composition of chick-peas, kidney beans, and lentils at various points in the preparation and cooking process: after soaking, after "normal" cooking (ie, boiling), after pressure-cooking, and after cooked legumes had been held at 35 degrees C for 5 hours. There was a considerable decrease in the amount of monosaccharides, disaccharides, and raffinose oligosaccharides in chick-peas and kidney beans after soaking and cooking. This change in carbohydrate composition was less pronounced when the cooking water was not drained before analysis, which was the method used when analyzing the lentils. Method of cooking (either boiling or pressure-cooking) did not have different effects on the sugar composition of chick-peas and lentils, but loss of oligosaccharides was slightly higher when kidney beans were boiled than when they were pressure-cooked. Loss of alpha-galactosides occurred in chick-peas and kidney beans that had been boiled and then held at 35 degrees C for 5 hours. The HPLC analysis showed that manninotriose was not one of the oligosaccharides present in these legumes.