Modification of sorghum starch as a function of pullulanase hydrolysis and infrared treatment

Papain-pretreated sorghum grains were modified by using pullulanase and infrared (IR) irradiation to decrease starch digestibility. An optimum synergistic effect was found under conditions of pullulanase (1 U/ml/5h) and IR (220 oC/3 min) treatment, which produced modified corneous endosperm starch with 0.022 hydrolysis rate, 42.58 hydrolysis index, and 0.468 potential digestibility. The modification increased amylose content and crystallinity up to 31.31 % and 62.66 %, respectively. However, the starch modification decreased its swelling power, solubility index, and pasting properties. FTIR revealed an increase in the ratio of 1047/1022 and a decrease in 1022/995, indicating the formation of a more orderly structure. The debranching effect of pullulanase was stabilized by the IR radiation amplifying its effect on starch digestibility. Therefore, the combination of debranching and infrared treatment could be an efficient method to produce 'tailor-made' starch, that can be further utilized in food industries to manufacture food for target population.