Resistant starch content, molecular structure and physicochemical properties of starches in Virginia-grown corn, potato and mungbean

Starches were isolated from Virginia-grown corn, potato, and mungbean, and their resistant starch content, molecular structure and physicochemical properties were investigated for potential applications. All starches, extracted with combination of chemical and physically method exhibited high purity with low protein, fat and ash, and high carbohydrate. Potato starches had the highest resistant starch content, while mungbean starches showed the highest amylose content. Amylose content as well as the starch granule size and structure were responsible for resistance to digestibility. Compared to their mungbean and corn counterparts, potato starches had the highest amylopectin molecular weights and largest granular size. A typical A-and B-type crystalline structure was assigned to corn and potato starches, respectively, while mungbean starches had a CA-type crystalline pattern. Both potato and mungbean starch granules were smooth, oval and irregular ellipsoids, while corn starches had polyhedral granules. The gelatinization transition temperatures (To, Tp, and Tc) of the starches were significantly different, with the order of corn> mungbean> potato. Water absorption capacity of corn starches was lower than that of potato and mungbean starches. The results would assist food scientists in determining the potential end-uses of starches.   Key words: Resistant starch, molecular structure, physicochemical properties, starch, Virginia.