胡芦巴半乳甘露聚糖的酶法改性及其产物表征

分别利用纤维素酶、普鲁兰酶及二者联用降解法对胡芦巴半乳甘露聚糖进行改性，并以原胡芦巴半乳甘露聚糖作对照，采用红外光谱(FTIR)、X- 射线衍射(XRD)、扫描电子显微镜(SEM)、热重法(TG)和差热分析法(DTA)对改性产物分子结构、结晶性能、形貌及热稳定性进行了表征。实验结果表明，不同酶解方法所得半乳甘露聚糖的黏均分子量分别为1.16 × 105、2.19 × 105、5.10 × 104，还原糖得率分别为5.1%、39.5%、43.8%。红外光谱分析表明，随着产物分子量的降低，糖类-OH 特征吸收峰及C-H 的变角振动吸收峰的强度逐渐增强，指纹区吡喃环特征吸收峰的强度逐渐减弱，但峰位置基本不变；XRD 分析表明，酶解作用对胡芦巴半乳甘露聚糖的结晶区的结构有一定的破坏作用，结晶度降低； SEM 分析表明，酶解作用对产物表面形貌影响显著，且对半乳甘露聚糖整体性严重破坏，颗粒粒度减小，表面孔隙减少；热分析图谱结果表明，随着产物分子量的降低，TG 曲线初始失重温度逐渐提高，总失重率降低，热稳定性提高；DTA 曲线放热峰顶温度逐渐降低，且峰强减弱。

Enzymatic Modification of Galactomannan from Fenugreek Seed and Characterization of Its Modified Products

The modification of galactomannan from fenugreek seed by cellulose, pullulanase or cellulose-pullulanase combination was introduced. Then the microstructure, particle shape, crystallinity and thermostability of original galactomannan and modified galactomannans were characterized with fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimeytry (TG) and differential thermal analysis (DTA). The results showed that the molecular weights of modified galactomannans are 1.16×105, 2.19×105 and 5.10×104, and the yield of reducing sugar are 5.1%, 39.5% and 43.8%, respectively. The analysis of FT-IR indicated that the chemical structures of residues are not modified during the hydrolysis process. The significant effects of degradation on the crystallized area of fenugreek gum can be observed by XRD analysis, and the degradation reaction mainly occurs in the non-crystalline region of fenugreek gum. SEM analysis showed that the whole molecular constitution is broken, and modified galactomannan granules are dissimilar in size with original galactomannan. According to the analyses of TG and DTA, the weight-loss temperatures of modified galactomannans increase, and they have higher thermostability and lower rate of weight loss.