Corn Starch Hydrolysis by Alumina and Silica-Alumina Oxides Solid Acid Catalysts

Starch is an abundant renewable resource and is the raw material for the production of a wide range of products, many of which are obtained by hydrolysis. While the hydrolysis of starch by enzymes and acids has been extensively investigated, there are scant studies with respect to the use of solid acid catalysts for this purpose. In this work, the features of corn starch hydrolysis by alumina (Al) and mixed silica-alumina (SiAl) oxides solid catalysts have been explored, as they are widely used due to their low cost and ease of synthesis. To this end, native corn starch (CS) aqueous dispersion (0.02 g g(-1)) is used as such or added with the Al or SiAl (1 g g(-1) starch), and gelatinized/hydrolyzed at 90 degrees C for 180 min. The effect of hydrolysis time on morphology (optical and SEM microscopy), hydrolysis progression (based on total sugar production), apparent amylose content, and starch crystalline structural changes (FTIR) is monitored. It is found that the acidity of the solid acid catalyst is a key factor that affected all of the above-mentioned parameters. The higher acidity (355.0 mmol NH3 center dot g(-1)) of SiAl produces higher maximum hydrolysis progression (90%) and apparent amylose contents (0.60 g g(-1) residual starch) than Al (70% and 0.40 g g(-1) residual starch, respectively), which exhibit lower acidity (84.0 mmol NH3 center dot g(-1)).