超声和微波辅助果胶酶处理对果胶结构的影响

Effect of ultrasonic and microwave assisted with pectinase treatment on pectin structure

以柑橘果胶为原料,对采用超声波和微波辅助果胶酶制备改性柑橘果胶的工艺条件进行了研究,并通过液相色谱仪、傅里叶红外光谱、扫描电镜对改性柑橘果胶和原柑橘果胶的理化性质和结构特性进行表征。结果表明,超声波和微波处理改性果胶时均能有效提高果胶酶的降解效率,几种降解方式得到的果胶的重均分子质量均比原果胶(283 kDa)低56.18%以上。超声、微波作用能显著提高半乳糖醛酸(galacturonic acid,GalA)的含量,微波处理酶解底物(MEPⅠ)、微波处理酶解产物(MEPⅡ)、超声波处理酶解底物(UEPⅠ)、超声波处理酶解产物(UEPⅡ)的GalA含量相比酶解果胶(39.57%)分别提高了52.31%、46.88%、66.69%、61.11%。不同的降解方法不改变果胶的单糖类型,但会使单糖的组成有差异,同时发现改性后果胶的主链和侧链发生不同程度的断裂,且酯化度减小。扫描电镜图可以看出果胶酶、微波、超声在不同程度上改变了柑橘果胶的微观结构。

Using citrus pectin as raw material,the process conditions for preparing modified citrus pectin using ultrasonic and microwave assisted pectinase were studied,and the physicochemical properties and structural characteristics of modified and original citrus pectin were characterized by liquid chromatography,Fourier infrared spectroscopy and scanning electron microscopy.The results showed that the degradation efficiency of pectinase could be improved by both ultrasonic and microwave treatment.The weight average molecular weight of the pectin obtained by several degradation methods was 56.18%which was lower than that of the original pectin(283 kDa).Ultrasonic and microwave effect can significantly increase the content of galacturonic acid(GalA),microwave processing enzyme substrates(MEPⅠ),microwave digestion product(MEPⅡ),ultrasonic treatment enzyme substrates(UEPⅠ),ultrasonic treatment enzymolysis products(UEPⅡ)GalA content than pectin enzyme solution(39.57%)increased by 52.31%,46.88%,66.69%and 61.11%respectively.Moreover,different degradation methods did not change the monosaccharide types of pectin,but made the composition of monosaccharides different.At the same time,it was found that the main chain and side chain of pectin were broken to different degrees after modification,and the degree of esterification was reduced.Scanning electron microscopy(SEM)showed that pectinase,microwave and ultrasound changed the microstructure of pectin in different degrees.