Impact of sprouting on the biochemical and nutritional features of legumes and pseudocereals

Legumes and pseudocereals are an excellent source of proteins, as well as of resistant starch, dietary fiber, minerals, vitamins, and phenolic compounds. Proteins in these seeds are composed mainly of globulins and albumins, whereas trigger proteins associated with celiac disease are absent. On the other hand, legumes and pseudocereals are often associated with a high content of phytates and protease inhibitors that can adversely affect nutrient bioavailability and protein digestibility. Germination is an inexpensive, sustainable, and effective method often used to improve the concentration and bioavailability of nutrients in foods, and reportedly improves the nutritional value of cereals and legumes by increasing protein digestibility while decreasing some anti-nutritional factors. In this study, we investigated the effect of sprouting on cowpea (Vigna unguiculata) and buckwheat (Fagopyrum esculentum) seeds by assessing the protein profile and hydrolysis along with the residual levels of phytates and trypsin inhibitors. After previous soaking, sprouting was carried out for 24, 48, and 72 hours on cowpea seeds, and for 48 and 72 hours on buckwheat seeds. After drying and grounding, protein profile and hydrolysis in the aqueous extract of the resulting flours were evaluated by SDS-PAGE and through the OPA assay for free amino groups. A commercial kit was used to assess residual phytate, whereas trypsin inhibitors were assessed according to the EN ISO 14902 standard. Release of water soluble phenolics was assessed by HPLC. The results showed that sprouting decreased in a time-dependent manner both the trypsin inhibitors activity and the phytic acid content. A concomitant increase in protein hydrolysis and in the amount of water-soluble phenolics was also observed. Of note, phenolics from aqueous extracts of flour from sprouted seeds were found to improve the hydrolytic activity of pepsin in a system based on various model substrate proteins. These results underline the possible relevance of sprouting as a simple, natural, and sustainable tool for improving the nutritional value of legumes and buckwheat, providing novel starting materials to produce foods with improved health impact.