谷朊粉/淀粉/甘油混合体系的流变行为与力学性能

研究了甘油增塑谷朊粉/淀粉混合体系的动态流变行为与单轴拉伸力学性能,考察了淀粉与水含量的影响.研究结果表明,含水量10%的混合体系储能模量(G′)随淀粉含量增大而增大,并在100℃出现橡胶平台.增塑谷朊粉在30℃呈现凝胶特性,在80℃出现交联网络结构.淀粉粒子可与小麦蛋白质形成复杂相互作用,阻碍蛋白质链段运动,导致模量与强度增加,断裂伸长率降低.含水量为20%与25%时,水份在淀粉粒子与蛋白质网络间起稀释和润滑作用,拉伸强度与断裂伸长率随淀粉含量的增高而降低.

RHEOLOGICAL BEHAVIORS AND MECHANICAL PROPERTIES OF GLUTEN-STARCH-GLYCEROL COMPOSITES

Recently the preparation of biodegradable materials using proteins from wheat,soy and corn has been widely studied due to their excellent cohesive,viscoelastic and gas barrier properties.The present work mainly focuses on the influences of starch and moisture contents on the dynamic rhelolgical behavior and uniaxial extensional deformation of glycerol plasticized gluten-starch composites. Wheat gluten,wheat starch and glycerol, compounds with weight ratio of 21∶0∶9,18∶3∶9,15∶6∶9,and 12∶9∶9,respectively,were prepared by using a three-roll mixer.The compounds were molded into rectangle-or dumbbell-shaped samples of 2 mm in thickness and 6 mm in width at room temperature.The dynamic behaviors of the mixtures were investigated using an Advanced Rheometeric Expansion System (ARES) at 0.1% strain and 30℃.The tensile test was performed on a universal testing machine with an extension rate of 20 mm min~ -1 . The results showed that the dynamic storage modulus (G′) of the composite increased with increasing starch fraction.The plasticized gluten forms a crosslinking network at 80℃ due to chemical reaction.The results of temperature scan revealed a "rubber plateau" at temperatures above 100℃.The starch gelatinization was not observed upon heating the composites.It indicates that moisture mainly exists in the glycerol-rich region, and the starch granules act as inert fillers.The dynamic frequency sweep shows that the composites exhibit gel-like behavior at 30℃.A marked "second plateau" appears in the low frequency region,which reveals strong physical interactions between the starch particles and the protein matrix.The interactions between polar groups in starch and protein both lead to the formation of a physical network additional to the chemical crosslinked protein network. The results of uniaxial extensional deformation tests show that the tensile strength and the elongation at break decrease with increasing the starch fraction in samples with 10% moisture.On the other hand,opposite results were observed in the composites containing 20% and 25% moisture,which could be ascribed to the dilution and lubrication between the starch granule and the gluten network by moisture.