Modification Of Galactomannan From Trigonella Foenumgraecum And Characterization

The factors,infuencing the decolorization effect of galactomannan extracted from the seeds of Trigonella foenumgraecum were studied by ethanol refluxing.The technological conditions were optimized by L₉(3⁴) orthogonal experimental design.In addition,different methods for deproteinization(Sevag and TCA) of the galactomannan were compared according to the residual ratio of the proteins and the loss of galactomannan.The results reveal that the optimal technological conditions for the decolorization as follows:ratio of feed to solvent 1:12,120 min each time,and should be for 3 times.TCA is simpler,more convenient and more efficient.FTIR results show that the peak of some absorptions sharpen after decolorization and deproteinization.The optimal hydrolyzes with hydrochloric acid,cellulase and pullulanase conditions of galactomannan from Trigonella foenumgraecum were investigated respectively by orthogonal design,taking the molecular weight of galactomannan and the yield of reductive sugar as indexes which were used to appraise the degradation effect.The results reveal that the optimal condition of degradation with hydrochloric acid are 1 g galactomannan degradated in 5 mol/L hydrochloric acid,at 70℃120 min,the molecular weight of product is 7.5×10³,the yield of reductive sugar is 14.6%.The hydrolysis was performed by adding 1500 U/g cellulase for the dissolved material in 100 mL of 0.2 mol/L acetic acid-sodium acetate buffer at pH 5.0 and incubating with continuous shaking for 150 min at 50℃.The molecular weight of product is 1.2×10⁵,the yield of reductive sugar is 5.1%.The hydrolysis was performed by adding 2000 ASPU/g of pullulanase for the dissolved material in 100 mL of 0.2 mol/L dibasic sodium phosphate-citric acid buffer at pH 5.2 and incubating with continuous shaking for 2 h at 60℃.The molecular weight of product is 2.2×10⁵,the yield of reductive sugar is 39.5%.The molecular weight of galactomannan which degradated with cellilase and pullulanase is 5.1×10⁴ and the yield of reductive sugar is 43.8%. Compared with original galactomannan,the solubility rate of low molecular weight galactomannan is increased.The microstructure,particle shape,crystallinity and thermostability of original galactomannan and hydrolyzates were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM), Thermogravimeyry(TG)and differential thermal analysis(DTA).FTIR results confirm that the residues chemical structures is not modified.XRD results show that the influences of degradation on the structure of crystallized area of the galactomannan was significant, crystallinity were reduced.SEM results show that the whole molecular constitution is broken,and modified galactomannan granules is dissimilar in size with original galactomannan.According to the results of TG and DTA,the weight lose temperature of hydrolyzates increases,and they have higher thermostability and lower rate of weight lose.