Polysaccharide Dry Heating Modification

In this paper, chitosan(CTS), Konjac glucomannan (KGM), and konjac oligosaccharides(KOS) was modified by phosphorylation, sulfation and selenium through dry-heating in the presence of glucose 6-phosphate,sodium pyrophosphate tetrabasic decahydrate,sodium pisulfate and selenius acid, respectively. Infrared spectra(IR), differential thermal analysis(DTG) and X-diffraction(XRD) studied their structure, qualitative description of its structure characteristics, and also discussed the modified konjac oligosaccharides antioxidant activity.Firstly, chitosan was modified with glucose 6-phosphate through Maillard reaction by dry-heating at 65℃for pH 7.0 and 2 days, which the content of phosphorus was 1.79%. IR spectra suggested that there was 1080 cm-1 near the strong absorption peak, which is the characteristic absorption peak of P=O. X-diffraction pattern showed that the part of crystalline of chitosan was changed to non-crystalline by phosphorylated. Differential thermal analysis showed that phosphorylated chitosan's temperature of maximum weight loss is 256.6℃, and stability lower than control chitosan, because of phosphorylase, which increased the negative charge of the chitosan and strengthened repulsion of chitosan. The flocculation ability of KGM was improved by phosphorylation.Secondly, chitosan was sulfated by dry-heating, the optimal condition was pH 3.0, 80℃, and the content of sulfate was 20.4%. The infrared spectra indicated that peaks at 1110 cm-1 from-OSO3-absorption, which showed that sulfate was introduced into the chitosan.Finally, KGM and KOS were selenited by dry-heating at 85℃for 2 days. The content of selenium was measured by ICP-AES, which were about 23.77% and 41.37%. Infrared spectra showed that 890 cm-1 near the strong peaks from Se=O absorption, which indicated that selenium have been received by KGM and KOS. We studied the physiological activity of selenium KOS importantly, such as antioxidant properties of selenium KOS, The DPPH radical scavenging compared with control chitosan was observed to high value. The reducing power of selenited KOS was better than that of unmodified one.In summary, polysaccharides can be successfully modified by dry-heating. Functional properties of modified polysaccharides have been improved. Dry-heating was proved an effective method for improving the functional properties of polysaccharide.