Effect of Preparation and Freezing Methods on the Concentration of Resistant Starch, Antinutritional Factors and FODMAPs in Beans

Abstract

Background: During frozen storage, the properties of vegetables are greatly influenced by storage conditions, especially temperature and time, even at low temperatures, suffering important quality attributes modification as a result of the action of biochemical activity, chemical and physical phenomena. The effect of freezing on common bean (Phaseolus vulgaris L.) and cowpea bean (Vigna unguiculata L. Walp.) processed under domestic processing conditions was evaluated to investigate the contents of resistant starch, oligosaccharides (raffinose and stachyose), phytate levels, protein digestibility and the inhibitory trypsin activity. Methods: The beans were cooked after different pre-soaking treatments and frozen (-20°C) for one, two and three weeks respectively. Results: A reduction was observed in the content of resistant starch by the use of the pre-soaking treatments; however, it increased significantly after freezing the samples from the treatments in which the soaking water was maintained and in which the cooked beans were frozen for 7 days. In the case of oligosaccharide content (raffinose and stachyose), cowpea beans had higher levels than the common beans, with changes in their values after 7 days of freezing. In the treatments in which the soaking water was discarded before cooking, raffinose and stachyose showed variable levels. In cowpea, the treatment in which the soaking water was not used in cooking showed a reduction in the content of phytate at 14 days of freezing, with inhibition of trypsin at 21 days compared with the initial time. Digestibility in all treatments was improved after freezing. Conclusion: The increase in resistant starch content, removal of phytate and trypsin inhibitors, and bean flatulence factors were significant in cooked beans after freezing between 14 and 21 days.