The Marrlid Reaction Of Chitosan Oligsccarids And The Antioxidant Activity Of It's Derivatives

Chitosan oligosaccharide (COS) is a water-soluble polysaccharide derived by the alkaline deacetylation and depolymerization of chitin, it is mainly composed of 2-10 glucosamine (GlcN) linked withβ-1, 4 glucosidic bond. As a natural antioxidant, COS has received considerable attention for the antioxidant activity, studies show that the antioxidant activity of COS can be changed by chemical modification, such as etherification, quaterisation, sulfation and graftcopolymerization. However, chemical modifications are generally not preferred for food application because of the formation of potential detrimental products. Owning to its large content of free amino groups, COS can also have Maillard reaction with reducing sugars. Currently, the use of Maillard reaction of COS received much more concern,studies are mainly focused on the functions such as ductility, emulsibility and antibacterial property, but less on the antioxidant activity.The goal of this paper was to obtain the COS derivatives by Maillard reaction, and to inspect their antioxidant activity. The derivatives were prepared by controling the ratio of amine group and carbonyl group, as well as the reaction times. This will give reference to the expanding of the COS modification and the development of natural and efficient antioxidants.The derivatives were prepared through Maillard reaction by heating COS with glucose, maltose and xylose, respectively. The pH, absorbance and fluorescence were determined during the reaction. The derivatives were characterized by FTIR and their molecular weight was determined by GPC. In addition, their antioxidant activities were evaluated by different measures. The main results are shown as following:1. During the Millard reaction, the pH declined obviously; both the UV-Vis absorbance at 278 nm and fluorescence at an excitation wavelength of 343 nm and an emission wavelength of 435 nm had a sharp increase; all derivatives showed the characteristic absorption bands of COS; the molecular weight of COS derivatives had increased via the Maillard reaction.2. The Maillard reaction of COS with glucose showed that all of the COS derivatives had strong antioxidant activity compared to COS; the COS derivatives prepared by 8 h had the better antioxidant activity than 4 h; the 1:1 system (the ratio of amine group to carbonyl group was 1:1) has the best antioxidant activity.3. The Maillard reaction of COS with maltose showed the derivatives of 3:1 system and 1:1 system had strong antioxidant activity compared to COS, while the antioxidant activity of 1:3 system declined.4. The Maillard reaction of COS with xylose showed: all of the COS derivatives had strong antioxidant activity compared to COS, the antioxidant activity was found to be CX13-4>CX11-4 and CX11-8>CX13-8, which indicated that the antioxidant activity of the chitosan oligosaccharide Maillard derivatives is not only related to the ratio of amine group to carbonyl group, but also related to the reaction times.5. The Maillard reaction of COS with glucose and maltose indicated that the derivatives prepared by monosaccharide had the better antioxidant activity.In this paper, the pH, absorbance and fluorescence were determined during the Maillard reaction of COS with reducing sugars, the structures of the COS derivatives were characterized and their antioxidant activity was investigated. The result of this paper indicated that the antioxidant activity of the COS derivatives may related to the reducing sugars, the reaction ratio of amine group to carbonyl group, as well as the reaction times.