高静压诱导苹果果胶流变特性变化机制研究

As a natural heteropolysaccharide, pectin has widely used in food industry as thickening, gelling and stabilizing agent etc. The methods of food process and pectin preparation have a significant effect on the structure and characteristic of pectin so as to effect the properties of pectin and food. High hydrostatic pressure technology (HHP) has draw worldwide attention recently because it can prolong the shelf life of fruit juice and maintain the smell, taste and nutrition of food without heating. Studies show HHP can change the rheological properties of juices and pectin, furthermore, pectin prepared by HHP has higher viscosity and better stability than others, however, the effect and mechanisms of HHP on the pectin structure and food stability under different conditions were not clear yet. The present proposal is planed to investigate the effect of HHP on the rheological properties under pectin solution with different pH and constitution, and through further analysis on physicochemical characteristics, pectin structures, so we will carry out a systematic study to reveal the effect and mechanisms of HHP on the rheological characteristics and pectin structures under the simulated juice and pectin preparation conditions. The results of this study can provide experimental and theoretical basis and have great significance on the selection of technologies and parameters of high quality pectin preparation and juice sterilization.

果胶是果蔬食品的重要组成成分，起到增稠、胶凝和稳定等作用。食品加工和果胶制备工艺均会影响其流变特性，从而影响果胶与食品的品质。高静压技术（HHP）作为最具应用前景的食品非热加工技术之一已得到世界范围的广泛关注。研究表明，HHP处理会影响果汁和果胶的表观粘度和流变特性，经HHP制备的果胶也具有粘度大，稳定性好等特点，而在果汁加工和果胶制备时，HHP对果胶流变特性变化的影响规律及相关机制尚不清楚。本项目拟以苹果果胶为原料，经柱色谱分离制备不同分子量分布的果胶组分，研究HHP处理对不同分子量果胶在提取体系和模拟果汁体系下流变特性的影响规律，并通过理化分析、结构测定、扫描探针成像等方法研究果胶理化性质、分子结构、聚集状态的变化，最终揭示HHP诱导苹果果胶流变特性变化的相关机制，为HHP技术在果汁加工和高品质果胶制备提供实践基础及理论依据，具有重要的理论和实际意义。

果胶是果蔬结构的重要组成成分，也是重要的食品添加剂，广泛应用到果蔬汁、乳制品、米面制品、肉制品的加工过程中，能够起到增稠、胶凝和稳定等作用。食品加工工艺和果胶制备工艺均会影响果胶的品质，从而影响果胶自身的理化特性和在食品中的应用品质。目前，果胶制备中除了传统的热提取法外，逐渐有些其他制备技术在研究和应用，比如酶法提取、微波提取、酸法提取等。高静压技术（HHP）作为最具应用前景的食品非热加工技术之一已得到世界范围的广泛关注。研究表明，HHP处理会影响果汁和果胶的表观粘度和流变特性，经HHP制备的果胶也具有粘度大，稳定性好等特点，而在果汁加工和果胶制备时，HHP对果胶的影响规律及相关机制尚不清楚。本项目应用高静压、闪式提取制备果胶与传统方法制备果胶进行理化性质、流变性质及乳化稳定性等进行了系统的对比研究，结果表明高静压、闪式提取制备果胶流变特性区别于传统提取方法的主要原因之一是传统长时间水浴加热可导致果胶分子的降解和功能特性的下降，所以本项目进一步开展了不同pH条件下水浴加热对果胶分子降解和分子结构形态的影响研究，进一步实验结果表明在pH=1.4和3.7条件下，果胶溶液经过85℃水浴加热0 - 100 min会导致果胶表观粘度和稠度系数降低，同时引起果胶流变特性指数增大，使果胶增稠效果减小，而果胶的半乳糖醛酸含量和酯化度均没有显著性变化；在pH=1.4时，果胶的分子量分布向低分子量端展宽，使果胶的平均分子量减小；而在pH=3.7时，果胶的分子量分布没有显著性影响；通过原子力显微镜观察在pH=1.4和3.7时，85℃水浴加热0 - 100 min均会导致果胶分子链内和链间发生聚集现象，引起果胶空间立体结构的减小，导致果胶表观粘度的降低。在pH=1.4条件下，部分果胶分子链发生断裂同时引起果胶分子的聚集；而pH=3.7时，果胶分子没有发生显著的降解，但分子内和分子间聚集现象明显增加，从而导致果胶溶液表观粘度降低。