Scanning electron microscopy and crystallinity of starches granules from cowpea, black and carioca beans in raw and cooked forms

Abstract

Beans are a vital food for the population around the world because it contains a relatively high amount of protein, vitamins, fiber, and minerals, being an important vegetable source of iron, particularly when combined with ascorbic acid and cysteine. The starch content in the seed is between 45 and 60%. This paper evaluated the granular structure of starches from common beans (Phaseolus vulgaris) and cowpea (Vigna unguiculata) in raw and cooked forms by Scanning Electron Microscopy (SEM), and their crystallinity by X-ray diffraction (DR-X). By SEM, was observed the occurrence of gelatinization phenomenon in cowpea and carioca beans, and the resistance to this event in black beans. By DR-X, the diffraction angles found in this work are more consistent with the classification of the standard polyphorm A. The Relative Crystallinity (RC) of black bean cowpea and carioca beans, observed by X-ray diffraction, varied significantly.