Abstract:

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.

Key words: galactomannan from fenugreek seed, cellulase, pullulanase, enzymatic modification