摘要
研究黄秋葵发酵酒渣果胶多糖的主要理化性质和流变学性质,结果表明:黄秋葵果胶多糖和黄秋葵酒渣果胶多糖的特性黏度[η]分别为41.12 dL/g和4.66 dL/g,黏均分子质量分别为1.466×106 g/mol和2.470×105 g/mol,黄秋葵经过发酵后的酒渣果胶多糖特性黏度的降低,但两者的Huggies常数相差不大,分别为0.59和0.55,说明2种分子链都具有较好的柔性;流动阶梯实验显示,黄秋葵发酵酒渣果胶多糖属于非牛顿流体中的假塑性流体,具有剪切稀化现象;将流动曲线拟合Cross模型,结合双对数曲线得到黄秋葵发酵酒渣果胶多糖的临界质量浓度c*约为4 g/dL,此时的分子空间占据量约为20,而黄秋葵果胶多糖并没有临界质量浓度c*。振荡实验显示其线性黏弹区域在2%~10%内均为线性。在振荡实验的温度范围内黄秋葵发酵酒渣果胶多糖是一种弱凝胶,没有明显的凝胶点。频率扫描实验表明黄秋葵果胶多糖溶液的储能模量大于耗能模量,说明其更多的表现出弹性而非黏性;黄秋葵发酵酒渣果胶多糖的耗能模量大于储能模量,其更多的表现出液体的黏性特征。Cox-Merz公式的拟合表明,黄秋葵发酵酒渣果胶多糖在低剪切速率下的复合黏度要大于稳态剪切黏度,表明其分子之间可能有新的结构生成,同时此结构对稳态剪切更为敏感。黄秋葵酒渣果胶多糖和黄秋葵果胶多糖酯化度分别为74.45%和55.817%,两者均为高酯果胶,前者的酯化度明显高于后者;从单糖组成可以看出,黄秋葵酒渣果胶多糖和黄秋葵果胶多糖均含有甘露糖、葡萄糖、鼠李糖、半乳糖醛酸、葡萄糖醛酸、半乳糖和阿拉伯糖,这表明这2种果胶多糖均属于酸性杂多糖,7种单糖组分分别占这2种来源的果胶多糖的52.3%和54.7%。根据单糖组分计算得到黄秋葵酒渣果胶多糖和黄秋葵果胶多糖的RG I组分分别为46.74%和90.00%,HG组分分别为16.76%和2.21%;两者的(Ara+Gal)/Rha比值分别为3.29和2.54,表明黄秋葵酒渣果胶多糖RG I的侧链长度或侧链数量要大于黄秋葵果胶多糖RG I的侧链。本研究结果可为黄秋葵发酵酒渣果胶多糖应用提供理论指导。
The physicochemical and rheological characteristics of pectic polysaccharides from okra wine pomace were studied.The results showed that the intrinsic viscosity[η]of the pectic polysaccharides from okra and from okra wine pomace were 41.12 and 4.66 dL/g,and the viscosity average molecular masses were 1.466×106 and 2.470×105 g/mol,respectively.The intrinsic viscosity of the pectic polysaccharide from okra wine pomace was lower than that of the pectic polysaccharide from okra,while Huggies constants were slightly different between the two samples,which were 0.59 and0.55,respectively,indicating that both have good molecular chain flexibility.The results of flow sweep experiments showed that the pectic polysaccharide from okra wine pomace was a non-Newtonian pseudoplastic fluid that had a shear thinning behavior.The flow curve was fitted to the Cross mode and on the basis of this model combined with the double logarithmic curve,we obtained a critical concentration c~*,about 4 g/dL,and the molecular space occupied was about 20 in the pectic polysaccharide from okra wine pomace,while there was no critical concentration c~*for the pectic polysaccharide from okra.The results of oscillation amplitude experiments showed that the linear viscoelastic region appeared within the strain range of 2%-10%.Furthermore,the pectic polysaccharide from okra wine pomace was a weak gel without obvious gelling point in the experimental temperature range.The results of oscillation frequency experiments showed that the storage modulus of the pectic polysaccharide solution from okra was greater than its loss modulus,suggesting that its elasticity was more dominant than its viscosity;the loss modulus of the pectic polysaccharide solution from okra wine pomace was greater than its storage modulus,showing that it was more prone to viscosity characteristics.Cox Merz model fitting showed that the complex viscosity of the pectic polysaccharide from okra wine pomace at low shear rate was greater than its steady shear viscosity,indicating that a new structure may be formed between its molecules,which was more sensitive to steady shear.The degrees of esterification of the pectic polysaccharides from okra wine pomace and from okra were 74.45%and 55.817%,respectively,and both of them were high-ester pectins.Monosaccharide composition analysis showed that the two pectin polysaccharides consisted of mannose,glucose,rhamnose(Rha),galacturonic acid(GalA),glucuronic acid,galactose(Gal)and arabinose(Ara),altogether accounting for 52.3%and 54.7%of pectin polysaccharides,respectively,indicating that both were acidic heteropolysaccharides.Based on the monosaccharide composition data,the proportions of rhamnogalacturonan I(RGI)in the pectin polysaccharides from okra wine pomace and from okra were 46.74%and 90.00%,respectively,the proportions of homogalacturonan(HG)were 16.76%and 2.21%respectively,and the ratios of(Ara+Gal)/Rha were 3.29 and 2.54,respectively.We speculated that the length or number of side chains of RGI in the pectin polysaccharide from okra wine pomace were larger than that in the pectin polysaccharide from okra.The results of this study can provide a theoretical guidance for the application of pectin polysaccharides from okra wine pomace.
作者
陈发河
周彦强
吴光斌
CHEN Fahe;ZHOU Yanqiang;WU Guangbin(College of Food and Biological Engineering,Jimei University,Xiamen 361000,China)
出处
《食品科学》
EI
CAS
CSCD
北大核心
2020年第22期64-73,共10页
Food Science
基金
厦门市科技计划项目(3502Z20173025)。
关键词
黄秋葵
酒渣
果胶多糖
流变学性质
okra
wine pomace
pectic polysaccharides
theological characterization