酸性条件下热处理对果胶流变和结构特性的影响

Effect of Heat Treatment under Acidic Condition on the Rheological and Structural Characteristics of Pectin

以柚皮为原料制备高分子质量果胶,研究酸性条件下热处理对果胶表观黏度和流变特性的影响,并通过测定果胶的半乳糖醛酸含量、酯化度和分子质量分布等理化指标,结合原子力显微镜扫描果胶分子结构状态的变化,揭示酸性条件下热处理对果胶流变和结构特性的影响规律及机制。结果表明,在pH 3.7条件下果胶溶液经85℃热处理0~100 min会导致果胶表观黏度明显降低,稠度系数显著降低(P<0.05),同时引起果胶流变特性指数显著性增大(P<0.05),果胶的半乳糖醛酸含量、酯化度和分子质量分布均无显著性变化(P>0.05),但果胶分子由分散和舒展状态转变为聚集状态,引起果胶空间立体结构的改变,从而导致果胶表观黏度和流变特性的改变,致使果胶的增稠效果减弱。

This study was implemented to investigate the effect of heat treatment under acidic condition on the rheological and structural characteristics of pectin and to unravel the underlying mechanism.After heat treatment under acidic condition,changes in the apparent viscosity and rheological properties of high-molecular-mass pectin from pomelo peel were examined as well as changes in some physicochemical measurements such as galacturonic acid content,degree of esterification and molecular mass distribution.We also investigated the structural changes of the pectin molecule using an atomic force microscope（AFM）.The results obtained showed that the apparent viscosity and consistency coefficient of the pectin declined significantly during 0–100 min of heat treatment at 85 ℃ and pH 3.7（P 〈0.05）,while the flow behavior index n increased significantly（P 〈0.05）.Nonetheless,there was no significant change in galacturonic acid content,degree of esterification or molecular mass distribution（P 〉0.05）.Moreover,the pectin molecule was changed from a dispersive and unfolded state to an aggregate state,altering the spatial structure and consequently the apparent viscosity and rheological properties and attenuating the thickening effect of the pectin.