Effect of Processing Methods on Mineral Bioaccessibility in Common Beans (Phaseolus Vulgaris L.)

Abstract Mineral bioavailability is a concern in legume based foods due to presence of Antinutritional factors. Zinc and iron deficiency is widespread in low-income countries because of the low consumption of animal products due to their unaffordable costs. The objective of this study was to evaluate the effects of processing conditions on the in vitro mineral bioaccessibility of small black common beans cultivated in Mozambique. The samples were collected from ‘Instituto de Investigação Agrária de Moçambique’ (IIAM), Maputo, Mozambique. Soaking (in water and sodium bicarbonate), germination (for 24 and 48 hours at 25oC), and cooking (ordinary and pressure) were applied. The oven-dried and finely ground samples of processed beans were in vitro digested and analyzed for mineral bioaccessibility. The in vitro gastrointestinal simulation assay was performed and the dialyzable part of the samples was used for iron, zinc, and copper bioaccessibility determination. Though there is a slight difference, all the processing methods investigated in this study; soaking, germination, and cooking treatments affected the mineral bioaccessibility of beans. The in vitro iron, zinc, and copper bioaccessibility was enhanced by the respective processing methods as compared to the control sample. The iron bioaccessibility was observed to be 2.22% for water soaking and 2.59% for sodium carbonate soaking, 2.75% for 24-hour germination 4.27% for 48-hours germination, and 3.56% for ordinary cooking and 7.79% for pressure cooking. The in vitro iron bioaccessibility is relatively low as compared to that of zinc. In vitro, Zinc bioaccessibility was found to be the same for water and sodium bicarbonate soaking which was 6.94%. Germination for 24 and 48 hours resulted in zinc bioaccessibility of 7.58% and 10.08% respectively while zinc bioaccessibility of 6.52% for ordinary cooking and 8.41% for pressure cooking was achieved. The respective in vitro copper bioaccessibility obtained for soaking in water and sodium bicarbonate was found to be 6.04% and 6.78% which are almost similar. Similarly, the germination for 24 and 48 hours showed copper bioaccessibility of 7.01% and 7.63% in respective order whereas it was observed that copper bioaccessibility of 5.79% for ordinary cooking and 8.50% for pressure cooking was achieved in this study. This shows that it is expected that the solubility of pressure-cooked beans in the intestine and the release of minerals from its matrix is high. The result illustrates that the pressure cooking of presoaked beans had the greater value for all mineral's bioaccessibility except for zinc, and it can be concluded that the processing techniques could help improve minerals' bioaccessibility in beans which in turn helps to combat malnutrition and ensure food security in developing countries.