| In order to use of the value of lysozyme better,this thesis used modified yam starch to immobilize lysozyme(LSZ-YS),then used LSZ-YS as raw material to prepare edible antibacterial film,and studied its physical and chemical properties and antibacterial performance.It was measured and finally applied to strawberry preservation.The specific research contents of this article are as follows:(1)The chemical modification method is used to modify the yam starch and immobilize lysozyme to provide raw materials for the preparation of edible bacteriostatic film.In order to ensure that the lysozyme can be stably immobilized,the effects of the EDC/NHS concentration,the amount of lysozyme added,the pH of the reaction solution,the reaction temperature and the immobilization reaction time on the immobilization capacity of lysozyme were investigated.The optimal parameters for obtaining modified starch immobilized lysozyme are as follows:EDC/NHS concentration 1.5 mg/mL,lysozyme addition amount 5.5 mg/mL,reaction solution pH value 7,reaction temperature 35°C,and immobilization reaction time 2 h.The solid loading was performed under this condition,and the solid loading was 91.97%at this time,which provided raw materials for the preparation of the edible antibacterial film.From the orthogonal test results,it can be concluded that the primary and secondary factors affecting the amount of solid loading are ranked as reaction temperature>lysozyme addition amount>EDC/NHS concentration>reaction solution pH value.The enzyme activity of modified starch immobilized lysozyme was 141560±51 U/mg,and 86.09±0.26%of the initial enzyme activity was retained after immobilization.(2)The lysozyme is immobilized according to the optimal immobilization conditions and used as the raw material for the preparation of edible bacteriostatic membrane.Using modified yam starch immobilized lysozyme(LSZ-YS)as raw material,taking the peroxide value as an indicator,the optimal film-making process is as follows:LSZ-YS addition amount 55%,glycerol addition amount 30%,Tween20 addition amount 0.05%,reaction temperature 25°C,stirring speed 180 r/min and reaction pH 5.And the performance of the preparation of antibacterial film was studied,the results are as follows:film thickness is 0.089±0.009 mm;film moisture content is 78.83±0.19%;film tensile strength is 44.32±0.84 MPa;film elongation at break is 31.08±1.01%;film transmittance is 81.32±2.03%;film water vapor transmission coefficient is 1.32±0.24 g.cm/cm~2.s.Pa;film oil permeability coefficient 0.36±0.08 g.mm/cm~2.d.By measuring the bacteriostatic ability of the bacteriostatic membrane,it is proved that the preparation of LSZ-YS into bacteriostatic membrane will not affect the bacteriostatic performance of lysozyme,and the bacteriostatic effect is better.(3)Finally,the modified yam starch immobilized lysozyme(LSZ-YS)was used to prepare the bacteriostatic agent for strawberry fresh-keeping experiments.By measuring the changes of sensory,weightlessness,texture,pH value and Vc content of the three groups of strawberry in the experimental group,control group and blank group,the fresh-keeping effect of the LSZ-YS bacteriostatic film was evaluated.LSZ-YS bacteriostatic film can not only prevent the reproduction of microorganisms on the surface of strawberries,effectively extend the shelf life of strawberries,but also prevent the reproduction of microorganisms on the surface of strawberries,effectively extend the shelf life of strawberries,and provide a basis for food antibacterial preservation. |
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