Study On The Antioxidantive Function Of Chitosan Oligosaccharide In Beer

As a natural alkaline polysaccharide, chitosan oligosaccharide had been proved to be a good antioxidant. The research to investigate the antioxidative function of chitosan oligosaccharide added in beer was performed in this paper. Firstly, an optimal method for the extraction, enrichment and determination of the content of aging substances in beer was established. Secondly, the fresh beers added with different dosage and different molecular weight of chitosan oligosaccharide respectively were forcibly aged for ten days at 37 o C,which were used to detect the content of aging substances. Finally, by comparing the content of aging substances, the dosage and the molecular weight of chitosan oligosaccharide for the beer with the best antioxidative function was determined.The 2 kDa chitosan oligosaccharide was added into the beer with four different doseage,such as 0.001%(w/v, the same below), 0.005%, 0.01% and 0.05%. The results showed,adding 0.001% or 0.01% of 2 kDa chitosan oligosaccharide into the beer has a better effect on the inhibition generation of beer aging substances. Then, three kinds of different molecular weight chitosan oligosaccharides(1 kDa, 2 kDa, and 3 kDa) were added to the beer with the dosage of 0.001% and 0.01% respectively. The experimental results showed that different molecular of chitosan oligosaccharide has different effect on inhibiting the production of beer aging substances, but 2 kDa chitosan oligosaccharide do the best. In summary, the beer adding with 0.001% of 2 kDa chitosan oligosaccharide by was believed to be the best in inhibiting beer aging, and the dosage of 0.001% can save the use-cost of chitosan oligosaccharide and reduce the cost of brewing beer.In order to study the antioxidative capacity of chitosan oligosaccharide, the DPPH free radical and hydroxyl free radical scavenging capacity were all investigated to analyzing the forcibly aging beers adding with different dosage and different molecular weight of chitosanoligo saccharide for ten days at 37 o C. The experimental results show that, the results detected with free radical mode were not consistent with that obtained from comparing the content of aging substances in beer. It can be inferred the antioxidative effect of chitosanoligosaccharide in the process of delaying the aging process of beer was not performed in the free radical mode, and its mechanism of antioxidative effect in beer needs to be further studied and discussed.2 kDa chitosan oligosaccharide was characterized by the ion chromatography, gel permeation chromatography, mass spectrometry and Fourier infrared spectrometry to detect its effective functional group, degree of polymerization, distribution range and so on. The experimental results showed that, the chitosan oligosaccharide is glucosamine polymers, and had a narrow distribution range(PD=1.653, medium distribution) which contains a small amount of impurities. With the occurrence of natural oxidation process, there were no significant changes in the structure of the internal functional groups of the chitosan oligosaccharide. Therefore, it was relatively stable in property and it can be used as a single factor, thereby determining chitosan oligosaccharide using the same structural characteristics in the preliminary experiment.In this study, adding chitosan oligosaccharide in the beer suppressed effectively the aging process of the beer. And it offered a valuable reference to the beer aging prevention and improvement in beer factory production.