Chlorella,as one of the high energy plants rich in polysaccharides,is always a hot spot for research by scholars,but there is relatively little research on the use of chlorella polysaccharides as preservation agents,so it is important to research and develop chlorella polysaccharide preservation agents.In this thesis,the extraction of polysaccharides was carried out by hot water extraction using Chlorella as the raw material.The extraction conditions were optimised by response surface methodology,and then combined with chitosan and alginose as a composite preservation solution to study the preservation effect of cold pork.The main studies are as follows.(1)The response surface methodology was used to optimize the hot water extraction of polysaccharides from Chlococcus sp.The single factor test showed that the extraction time was 4 h,the solid-liquid ratio was 1:20,and the temperature was 90℃.Are combined on the basis of the above conditions,the design,selection of independent variables for the extraction time,temperature,liquid ratio and the selection of the response value of polysaccharide extraction yield,three factors and three levels on the response variable analysis,get the optimal conditions for temperature 91℃,material liquid than 1:21.50,extracting time 3.85 h,measured polysaccharide extraction yield up to 5.53%.(2)The content of D-mannose,glucuronic acid,glucose,galactose,xylose and arabinose were 1.57×10~4 mg/kg、3.57×10~3 mg/kg、8.45×10~4mg/kg、1.01×10~4mg/kg、4.68×102mg/kg、2.97×103mg/kg,and the antioxidant index of Chlorella polysaccharides was determined,in which the hydroxyl radical scavenging ability reached 98%at 20 mg/m L,the DPPH radical scavenging ability reached 98.69%and the reducing ability was 0.64.The scavenging rate of superoxide anion radical at1mg/m L was 90.15%and the scavenging rate of ABTS radical was 80.10%,indicating that Chlorella polysaccharide has certain antioxidant effect.It can be used as a preservative in food.(3)Through blank group,green algae polysaccharide group,chitosan group,trehalose group and compound group,the fresh-keeping effect of chilled pork was studied.The optimal ratio was 1.50%green algae polysaccharide,1.10%chitosan and 0.95%trehalose.The total number of bacteria,TVB-N value,p H value,juice loss rate and sensory score of chilled pork treated with compound preservative on day 10 were significantly lower than those of control group and single experimental group(P<0.05),which could effectively prolong the shelf life of chilled pork to day 10.The above tests provide a data base for subsequent development and a theoretical basis for further research on green algae. |