Effects of pyroconversion and enzymatic hydrolysis on indigestible starch content and physicochemical properties of cassava (Manihot esculenta) starch

Cassava (Manihot esculenta Crantz) root is the second most important starch source worldwide and its cultivation could be potentially much greater. Pyrodextrins and enzyme-resistant maltodextrins were produced from cassava starch by pyroconversion and enzymatic hydrolysis. Changes in indigestible starch content and some physicochemical properties were analyzed. The best results were produced with a 160:1 (m/v) starch:HCl ratio, 90°C temperature, and 3 h reaction time. These conditions produced a pyrodextrin with 45.98% indigestible starch content and a color difference of 1.89. Optimum hydrolysis conditions were a 0.01% α-amylase concentration and 5 min reaction time, which produced a resistant maltodextrin with 24.45% dextrose equivalents and 56.06% indigestible starch content. Compared to the native starch, the pyrodextrin exhibited 93% solubility at 60°C, and 100% at 70–90°C. The resistant maltodextrin was completely soluble at all temperatures. The pyrodextrin had low water-absorption capacity (0.16–0.34 g water/g gel) and some swelling power, while the resistant maltodextrin had neither property, even at low temperatures. None of the compounds exhibited a gelatinization transition. The resistant maltodextrin's high indigestible starch content and solubility make it a promising ingredient for increasing dietary fiber content in a wide range of foods, particularly beverages, creams, soups, dairy and bread products.