Effect of cooking on the bioaccessibility of essential elements in different varieties of beans (Phaseolus vulgaris L.)

The chemical composition of beans (Phaseolus vulgaris L.) provides several health benefits to humans. However, cooking beans before consumption is necessary to reduce the effect of certain toxic and anti-nutritional substances and to increase protein digestibility. However, heat treatment of beans may alter the chemical composition and nutrient bioaccessibility. In this study, the effect of cooking on elemental bioaccessibility in seven varieties of Phaseolus beans (common, black, fradinho, rajado, bolinha, jalo, and rosinha) were evaluated. In vitro gastrointestinal digestion of raw and cooked beans was performed to evaluate the bioaccessibility of calcium, copper, iron, sulfur, and zinc, combined with elemental determination using inductively coupled plasma optical emission spectrometry. The gastrointestinal digestion of raw and cooked grains showed that the cooking decreased the percentage of soluble iron in the fradinho (29%), rajado (27%), bolinha (20%), and rosinha (7%) varieties. The percentages of elemental bioaccessibility for raw or cooked black beans showed that sulfur (93%, raw and cooked) and copper (88% for raw and 89% for cooked) were the most bioaccessible essential elements; in contrast, calcium (41%) was the least accessible element in cooked grain.