Influence of different conventional processing methods on the resistant starch content and diastatic power of Bambara groundnut (Vigna subterranean) starch

Abstract

The edible seeds in the pods of legumes have been used in the management of protein-energy malnutrition after undergoing food processing operations to promote their utilization. However, starch were obtained from the raw seeds when subjected to operations like drying, germination, soaking, boiling, and milling. Therefore, this study investigated the effect of conventional processing methods such as drying, boiling, and germinating on the starch qualities of Bambara groundnut for value addition in the food system and healthy therapy. The seeds were divided into four batches (native, boiled, germinated and dried) while starch was isolated from each using alkaline methods and the products were compared in terms of starch yield, color, amylose content, resistant starch, and diastatic power. The starch yield was 38, 32 and 28% for the germinated, dried and boiled samples, respectively when compared to the native sample (44%). The higher lightness (whiteness) obtained for the native starch (84.57) over the processed starches was due to its low pigmentation level.  Meanwhile, the amylose contents of native and processed starches were in the range of 26.48 to 27.49%. The resistant starch ranged from 17.56 to 18.03%, with cooking (boiling) process significantly increasing the resistant starch contents, which may be attributed to the effect of retrogradation on the boiled starch after cooling. Contrarily, the diastatic power was very high in the germinated starch sample (9.34 ^oL) when compared with other samples due to the malting or germination process of the seeds before starch extraction. However, the information generated from this study could be useful for indigenous promotion and effective utilization of Bambara groundnuts both domestically and industrially as a functional and nutraceutical food.