Effects of Extrusion Technology Combined with Enzymatic Hydrolysis on the Structural and Physicochemical Properties of Porous Corn Starch

Effects of the combination of extrusion pretreatment and enzymatic hydrolysis on corn starch are investigated through its microstructural and physicochemical properties. This combined modification resulted in the formation of more pores on the surface of native starches (NS), as revealed by scanning electron microscopy (SEM). Compared with either single-treatment modified starch samples, starch that was bioextruded and treated by enzymatic hydrolysis achieved higher crystallinity, more uniform pore structure, and higher gelatinization temperature than those of native porous starch, as determined by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and differential scanning calorimetry (DSC). Low-temperature nitrogen adsorption experiments showed that the specific surface area (2.52 m2/g), total pore volume (4.53 × 10−3 cm3/g), and average pore size (7.36 nm) of porous starch were significantly increased by bioextrusion combined with enzyme hydrolysis (P < 0.05). The results of hydrolysis degree (DH) also showed that bioextrusion could improve the efficiency of hydrolysis. Starch that was bioextruded followed by enzyme hydrolysis showed the highest adsorption capacity in adsorption tests of adsorption of oil (63.29%), water (162.61%), and methylene blue (6.04%). The present study suggests that the combination of bioextrusion pretreatment and enzymatic hydrolysis is an attractive alternative for preparing porous corn starches.