| Chitin as one of the important fibrous substance consisting of polysaccharides is obtained from the hard outer skeleton of sea food with the content as high as about40% in dried shrimp and crab shells.Chitosan is a a linear polysaccharide obtained after alkaline treatment of the chitin shells of shrimp.This dissertation focuses on the preparation,physicochemical properties,antioxidant properties,bacteriostatic properties,and the preservation effect of different Maillard reaction products of shrimp chitosan on beef.The results of the paper establish the basis for the extended use of shrimp chitosan in the food industry.Enzymatic hydrolysis of shrimp shell deproteinization process optimization and preparation of chitosan.Firstly,the process for removing shrimp shell protein with acidic enzymes was optimized.The optimal process conditions were enzyme addition2.16%,50.5 °C,65 min,and p H 3.0.Under this condition,the shrimp shell deproteinization rate was 78.9%.Chitosan was further prepared using deproteinized shrimp shells.The extraction rate of chitin was 62.6%,and the yield of chitosan was34.2%.Antioxidant Study of Chitosan Maillard Reaction Products.The prepared chitosan was subjected to Maillard reaction with xylose,fructose,and glucose to prepare xylose-chitosan(Xy-MRPs),fructose-chitosan(Fru-MRPs),and glucose-chitosan.(Glu-MRPs)Maillard products;and the identification of the three products was carried out using fluorescence,ultraviolet,and infrared spectra.The Maillard reaction products of different reducing sugars and chitosan were found to be closely related to the reaction time.The solubility of xylose-MRP was significantly lower than glucose-MRP and fructose-MRP,but the oil holding capacity was significantly higher than glucose-MRP and fructose-MRP.The Maillard reaction product of chitosan and three reducing sugars exhibited high oxidation resistance,which was varied with the detection index.The order of total reducing power was xylose-MRP> fructose-MRP>glucose-MRP.The apparent scavenging power order of DPPH free radicals was xylose-MRP> glucose-MRP> fructose-MRP.And the order of ABTS free radical scavenging ability was Xylose-MRP ?Glucose-MRP> Fructose-MRP.The order of the ability to scavenge hydroxyl radicals was Xylose-EMP>Fructose-MRP?Glucose-MRPs.Antibacterial and preservative performance of Chitosan Maillard reaction products(Glu-MRPs and Fru-MRPs).The antibacterial activity of highly soluble Glu-MRPs and Fru-MRPs against these common pathogens such as Staphylococcus aureus,Salmonella typhi,Bacillus subtilis,and Escherichia coli was investigated;and the preservation effect of Glu-MRPs and Fru-MRPs on fresh beef was also studied.The two MRPs(Fru-MRPs and Glu-MRPs)could inhibit the growth of the four tested bacteria;while the bacteriostatic effects of the two products were slightly different.The order of bacteriostatic activity of Glu-MRPs was S.aureus>E.coli>B.subtilis>S.typhi;while for Fru-MRPs,the order was S.aureus>B.subtilis> S.typhi > E.coli.Treating beef with chitosan(Chitosan)and its Maillard reaction products(Fru-MRPs,Glu-MRPs)could significantly reduce the volatile base nitrogen(TVB-N),trimethylamine(TMA),p H and total bacterial count(TBC)which resulted into improved sensory evaluation score.Fru-MRPs and Glu-MRPs have stronger inhibitory or promotion effects than chitosan.In addition,chitosan was able to extend the shelf life of fresh beef for two days,and the Maillard reaction products of Chitosan(Fru-MRPs,Glu-MRPs)could extend the shelf life for four days,and the effect of Fru-MRPs was somewhat better than Glu-MRPs.The above results indicate that the Maillard reaction product of shrimp chitosan and reducing sugar had high antioxidant,bacteriostatic,and preservative effects on fresh beef.The preservative effect of chitosan-Maillard reaction product was stronger than the chitosan alone.These result pave a way forward for the application of shrimp shell chitosan as a novel preservative agent in the food industry. |
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