Study On The Preparation Of Chitosan From Shrimp Shell And The Application In Antibacterial And Water Retention

A new method of chitin extraction process has been proposed based on the recent research of chitosan from shrimp shell resources,through which chitosan with higher degree of deacetylation has been prepared.Combining collagen peptide and sodium chloride,a non-phosphate additives has been developed upon the good moisturizing effect of chitosan,which proved to be security and efficient applied in food field.Meanwhile,a new kind of permeability film with good antibacterial and physicochemical property has been synthesized through adding natural cinnamon oil to compound substrate of chitosan and gelatin based on their good film-forming characteristics.The main results of the research are shown as follows:1.Mixing malic acid with citric acid in a certain proportion to decalcified shrimp shell,and the decalcification rate can up to 99%;Selecting neutral protease as the optimum enzyme to hydrolyze Shrimp shell protein,and under the optimum conditions of enzymolysis,the deproteinization rate arrived 72.69±0.36%,which was no significant difference with conventional alkali boiling protein method(75.24±1.48%).The method is a mild process,which can reduce the pollution of the environment,and improve the efficiency of extracting chitin greatly.2.The deacetylation process was optimized to produce chitosan with high degree of deacetylation by Doehlert Design,the result showed that the optimum conditions were solid-liquid ratio of 1:38(g/mL),heating time of 6 h,NaOH concentration of 45%,temperature of 125 ℃,intermittent treatment.The produced chitosan with high degree of deacetylation 98.89±1.01%,which was higher than that in the traditional preparation way by13.72%.The molecular weight(Mw)of chitosan prepared by the optimal process conditions was 148 KDa.3.Preparation and optimization of non-phosphate additive.Single factor and orthogonal experiments were used to determine the optimal formula of water retention agent:chitosan of 0.6%,collagen peptide of 2.0%,sodium chloride of 0.5%.The shrimp were soaked in optimization water retention agents by 80 min,which showed a better effect of water retention by the comparison with commercially available compound phosphate.The non-phosphate additives improved the water retention of shrimp is due to the aquasorb can get into the shrimp’s internal by osmosis,bind with muscle protein,and enhance the stability of the structure.4.Preparation and optimization of chitosan antimicrobial preservative film.Single factor experiment and response surface method showed that the optimal technological parameters of the preparation were:the ratio of chitosan and gelatin is 5:5,glycerol content of 25%(W/W chitosan),cinnamon essential oil content of 0.4%(W/Wmix),heating temperature of 60℃ and heating time of 30 min.And the main properties of the optimum composite film were as follows,thickness of 45.43±3.11 μm,tensile strength of 42.17±1.84 MPa,elongation at break of 62.34±2.66%,water vapor transmission rate of 0.030±0.018 g ·mm/KPa ·h ·m2,water content of 26.39±3.07%,degree of swelling of 0.49±0.12,solubility of 13.32±0.70%.The composite film showed a good characteristic and can be used to package food.5.The structural of the composite film was characterized using Scanning Electron Microscope,Atomic Force Microscope,X-Ray Diffraction,Fourier Transform Infrared Spectroscopy,Thermogravimetric Analysis,and Contact Angle.The results showed that there is a good compatibility among chitosan,gelatin,and cinnamon oil.The morphology of composite film was smooth and flawless.Compared with chitosan film,the crystallinity of composite film was reduced,thermal stability was improved,and hydrophobic property was enhanced too.6.Bacteriostatic effect of different three kinds of membrane samples against gram-negative bacteria and gram-positive bacteria were determined respectively.The results showed that the antimicrobial activity of composite film was improved significantly by adding of cinnamon oil,and antibacterial rate against two kinds of bacteria both exceeded 98%.In addition,the minimum inhibitory concentration against two kinds of bacteria were both 52.06 μg/mL,and the minimum bactericidal concentration were 104.12 μg/mL and 52.06 μg/mL respectively.