As a simple and effective physical method, ultrasound irradiation has been used to modify starch. Native waxy corn starch was treated by ultrasound irradiation at 100 and 400 W in this study. Compared with native waxy corn starch, lower proportion of B1, B2, and B3, higher proportion of A chain were observed in ultrasonicated waxy corn starch. 1H NMR combined with HPSEC-MALLS-RI data showed that lower degree of branching was observed in ultrasonicated waxy corn starch, and α-1,4 glycosidic linkages were more stable than α-1,6 glycosidic linkages in waxy corn starches. 13C NMR data indicated that the content of double helices was decreased, and single helix and amorphous components were increased after ultrasound irradiation. The A-type crystal structure was scarcely affected according to X-ray diffraction (XRD) analysis. The granule surface of ultrasonicated waxy corn starch became notch and rough fragment, and lower particle diameter was observed in ultrasonicated waxy corn starch. These results demonstrated that ultrasound irradiation affected chain length distribution, double helices, single helices and amorphous state, especially α-1,4 glycosidic linkages and α-1,6 glycosidic linkages, of waxy corn starch.

Glucoamylase enzyme is one of the most important enzymes. It catalyzes the hydrolysis of starch into soluble sugars. It was covalently immobilized onto κ-carrageenan gel beads after activation by using polyethylenimine (PEI) followed by glutaraldehyde (GA). All parameters in activation process were studied. The immobilized enzyme shows enhancement in temperature profile as the optimum temperature for the free enzyme was 60 °C, and it becomes 60–80 °C that means broader range and also shows stability in acidic conditions more than free enzyme. The apparent Km of immobilized enzyme, 147.46 mM, becomes higher than Km of the free one, 110 mM and the maximum reaction velocity (Vmax) values for the immobilized enzyme decreased from 2.28 to 1.11 μmol min−1. The immobilized enzyme can be reused and kept its activity (100%) till 11 successive cycles. The immobilization process steps were characterized by FTIR and SEM. These results confirm the economic and biotechnical benefits of enzyme immobilization, particularly with regard to the number of enzyme reuses, which open the possibility of different industrial applications.

Raman spectroscopy is critically evaluated to establish the limits to which it may be used to detect changes in protein conformation upon extrusion. Rice bran protein (RBP) extruded with different temperatures (100, 120, 140, and 160°C, labeled as ERBP-) was considered. DSC showed that extrusion at 100°C increasedTDof RBP but decreased itsΔH, while, after extrusion treatment at 120°C, RBP completely denatured. A progressive increase in unordered structure and a general decrease inα-helix structure andβ-sheet structure of extruded RBP were observed from Raman study. Meanwhile the content of unordered structure increased up to 140°C and then decreased at 160°C, while the trend ofα-helix andβ-sheet content was opposite, which was contributed to the composite effect of formation of some more protein aggregation and protein denaturation. Extrusion generally induced a significant decrease in Trp band near 760 cm⁻¹but an increase at 160°C. No significant difference was observed in Tyr doublet ratios between controlled RBP samples and extruded RBP below 160°C, whereas Tyr doublet ratios of extruded RBP decreased at 160°C. Intensity of the band assigned toCHnbending decreased progressively and then increased as extrusion temperature increased, indicating changes in microenvironment and polarity.