Effects of α-Amylase, Amyloglucosidase, and Their Mixture on Hierarchical Porosity of Rice Starch

Porous starch is produced by enzymatic hydrolysis of rice starch at sub-gelatinization temperatures, applying reaction times of 3, 6, and 12 h, respectively. The effects of alpha-amylase (AM), amyloglucosidase (AMG), and their mixture (AM + AMG) on starch are studied by morphology, hierarchical porosity, granular structure, and thermal and surface stability. The reaction time of 6 h is found to be the more appropriate for the three enzymatic treatments studied. The techniques used to characterize the porous starches reveal porosity distribution is present in all samples. It is possible to identify the presence of macropores (scanning electron microscopy), mesopores (porosimetry of nitrogen), and micropores (adsorption capacity). The addition of AM suggests the formation of a higher micropores fraction, whereas the AM + AMG mixture contributes to the development of more mesopores and macropores fractions. The particle size distribution, gelatinization temperatures, and zeta potential modulus results indicate that porous starches prepared in this way, can be useful as a thermoresistant and stable adsorbent in food and chemical applications.