Study On Chitosan As A Natural Food Preservative

Chitosan is nontoxic and safe, and has been approved to be food stabilizer. However, thisnatural polysaccharide has been documented to have the antimicrobial effect which varies with itsmolecular weight and deacetylation degree. The purpose of the present study is to find a type ofchitosan which had good antimicrobial effect and solubility and then confirm its molecular structure,physicochemical properties and production. Meanwhile, according to the rule of declaring andaccepting food additive, chitosan will be declared as food preservative.The relationship between the structure and antimicrobial activities of these chitosans wasexamined against three bacteria (Staphylococcus aureus,Escherichia coli and Salmonella) and twofungi (Saccharomyces cerevisiae and Aspergillus niger).The result showed that the antimicrobialefficiency increased with degree of deacetylation (DD) increasing. Chitosans showed higherantibacterial effects with bacteria than did with fungi. Among three bacteria, Staphylococcus aureusshowed higher sensitivity to chitosans than Escherichia coli and Salmonella. Chitosan hydrolyzed6h(viscosity average molecular weight was 1.53×105) showed the highest antibacterial activity toEscherichia coli in the MIC of 0.05% and chitosan hydrolyzed 10h(viscosity average molecularweight was 5.8×104) showed the highest antibacterial activity to Staphylococcus aureus in the MICof 0.01%. Chitosans hydrolyzed 8h(viscosity average molecular weight was 9×104) showed thegood antibacterial activity to Escherichia coli and Staphylococcus aureus. Comparing with otherfood preservatives, chitosans within this molecular weight range were found the similarantibacterial effects.Chitosan was hydrolyzed by radiation with 60Co-γ-ray and acid respectively. The twomethods were compared to the effect on the physicochemical properties and structure of chitosans.The results exhibited that the solubility and the content of reduced sugar of chitosan produced byacid hydrolysis were higher than that of chitosan produced by radiation hydrolysis. Chitosanprepared by radiation hydrolysis had decreased the molecular weight while the reduction ofmolecular was lower, which illustrated that radiation hydrolysis had the effect on the structure ofchitosan molecular. After the comparison to the two methods, the production of chitosan preparedby acid hydrolysis was confirmed considering to the safety of chitosan.The physicochemical properties and structure of chitosan which was used as food preservativewere determined and substantiated. The results showed that chitosan had high thermaldecomposition temperature and was suitable to be applied to the hot working food. Moreover, itwas dissolved easily in acidic foods and convenient to put to use. The method of detection wasconfirmed. The quality standard and analysis methods of chitosan as food preservative wereestablished .Chitosan was applied to the liquid and solid food such as torfu, meat products and sauce andcompared with common food preservatives. The range and quantity of usage were confirmed. Afterthe determination of the physicochemical properties, microorganism index and preservation time offoods, the results showed that chitosan had the equivalent antimicrobial effect to potassium sorbateand was an ideal natural food preservative.