| Nisin is a natural antibacterial peptide widely used in the food industry.Factors such as enzymes and lipids in the food system will affect the antibacterial activity of nisin and limit its industrial application.In order to improve the stability and activity of nisin in food application,we used the method of adding protective agent and preparing nanoemulsion to improve the antibacterial activity of nisin.?-cyclodextrin??-CD?has an external hydrophilic and internal hydrophobic chiral cavity structure,which can form inclusion complexes with small molecules such as organics or inorganic substances.However,whether?-CD has a protective effect on nisin has not been reported.On the basis of studying the protective effect of?-CD on nisin,we prepared nisin stabilizer from?-CD and studied its protective mechanism,and the main research contents are as follows:1.The protective effect of?-CD on Nisin?1?The protective effect of?-CD on nisin was studied for the first time with Micrococcus luteus as model strain.The effect of?-CD on nisin was investigated under different p H and temperature conditions,even in the presence of trypsin.The results showed that in the presence of trypsin,the Nisin titer at a 1/2 ratio of?-CD was not significantly reduced,indicating that?-CD had a protective effect on the antibacterial activity of nisin.?2?The protective effect of?-CD on nisin was evaluated by measuring the number of colonies?TVC?and volatile basic nitrogen?TVB-N?in the storage experiment of meat products.The results of 40 day storage experiment showed that adding?-CD to nisin could delay the growth of bacteria and improve the antibacterial activity of nisin.The result of TVB-N was consistent with that of TVC.Even in the presence of trypsin,?-CD can significantly reduce the loss of nisin titer in the enzyme environment.?3?Spectroscopic analysis?ultraviolet spectrum,fluorescence spectrum?showed that as the?-CD concentration gradually increased,the intensity of the characteristic absorption peak of nisin showed a regular upward trend.It is shown that?-CD interacts with nisin to form a complex,which changes the microenvironment and spatial conformation of nisin.In addition,the results of electrophoresis showed that?-CD could improve the stability of nisin,and the results of electron microscope analysis also showed that the combination of nisin and?-CD could better maintain the structure of meat products.2.Preparation and characteristics of Nisin nano-formulation?1?Nisin emulsions were prepared from nisin,?-CD,sodium alginate?SA?and calcium chloride?Ca Cl2?.The results showed that the best sustained-release nisin nanoemulsion can be prepared when the ratio of the selected materials is 0.5%?-CD,1%nisin,1.5%sodium alginate and 0.75%calcium chloride,and the encapsulation efficiency of nisin can reach 61.58%.?2?Spectroscopy analysis showed that the Nisin-?-CD group has the highest absorption intensity at the characteristic absorption peak than the nisin control group.In addition,the strength of nisin,nisin emulsion,and nisin-?-CD emulsions containing emulsion systems were low.The absorption intensity of?-CD emulsion at the characteristic absorption peak of nisin was also higher than that of nisin emulsion.The nanometer size of the preparation was 268.13±56.43 nm by particle size analysis.Potential analysis showed that there was a weak electrostatic interaction between the emulsion system and nisin.Based on the study of the protective effect of?-CD on nisin,a new type of nisin stabilizer was prepared with?-CD as the main raw material,which provides a theoretical basis for expanding the application of nisin in the field of food. |
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