超声处理对葡萄细胞壁果胶组分的影响

Effect of Ultrasonic Treatment on Vitis vinifera L.Cell Wall Pectin Components

为明确超声处理下葡萄细胞壁中不同果胶组分含量及结构变化,本研究采用不同超声时间和超声功率对葡萄进行处理,通过咔唑硫酸法、PMP柱前衍生化法、高效液相凝胶色谱分析、扫描电子显微镜、傅里叶变换红外光谱分析和圆二色谱分析等手段分析了葡萄细胞壁中果胶组分含量、单糖组成及结构变化。结果表明,新鲜葡萄细胞壁果胶中碱溶性果胶含量最高,为27.41 mg/g AIR,螯合型果胶含量最低,为8.25 mg/g AIR;不同超声处理后总果胶含量呈下降趋势,其中水溶性果胶含量增加,螯合型和碱溶性果胶含量降低。果胶单糖共检测到6种,不同果胶组分单糖组成不同,水溶性果胶中半乳糖和阿拉伯糖含量较高,螯合型果胶中葡萄糖醛酸含量最多,而碱溶性果胶中含量最高的为鼠李糖;超声处理后果胶组分单糖组成不变,但含量均发生降低;超声作用未改变果胶主链结构,但其线性结构和支链程度均发生变化。随着超声处理时间和功率的增加,不同果胶的分子量整体均呈下降趋势,并且在微观结构上呈现更加松散形态。此外,超声作用对果胶组分特征官能团影响较小,但对螯合型果胶和碱溶性果胶分子的结构和链构象产生作用,使其最大响应值发生移动,并且超声功率作用影响更大。超声作用可使葡萄细胞壁中果胶含量及单糖含量降低,并影响果胶分子线性结构和分子链构象。该结果可为进一步研究超声处理下葡萄干制品品质变化提供理论依据。

In order to clarify the content and structural changes of different pectin fractions in grape cell walls under ultrasonic treatment,the grapes were treated with different ultrasonic time and ultrasonic power in this study,and the content of pectin fractions,composition of monosaccharides and structural changes of grape cell walls were analyzed by means of carbazole sulfuric acid method,PMP pre-column derivatization,high-performance liquid gel chromatography,scanning electron microscopy,Fourier transform infrared spectroscopy and circular dichroism.Results showed that the highest and the lowest contents in fresh grape cell walls were alkali-soluble pectin(NSP)and chelate pectin(CSP),respectively,and they were 27.41 mg/g AIR and 8.25 mg/g AIR.The total pectin decreased after ultrasonic treatments,in which the water-soluble pectin(WSP)increased and the CSP and NSP decreased.A total of six monosaccharides were detected in three pectins,and the monosaccharides of different pectin were not the same.The galactose and arabinose were high in WSP,the glucuronic acid was the most abundant of CSP and the rhamnose were the highest in NSP.After ultrasonic treatment,the contents of monosaccharides decreased,while the composition did not change,and the main chain structure of pectin was no change,but the linear structure and the degree of branch chain were changed.With the increase of ultrasonic times and powers,the molecular weight of different pectins declined gradually.And in the microstructure showed a more loose morphology.In addition,ultrasonic treatment had an effect on the structure and chain conformation of CSP and NSP,which made their maximum response values shift,and the effect of ultrasonic power was more significant.In conclusion,ultrasonic treatment could reduce the pectin and monosaccharide contents in grape cell walls,and affect the molecular linear structure and molecular chain conformation of pectin.These results can provide theoretical basis for the quality change of grape products under ultrasonic treatment.