| Hexahydro-?-acids(HBA)is a derivative of?-acids,which is an important component of hop soft resin.HBA has good stability,antibacterial activity,antioxidant activity,hypoglycemic activity and anticancer activity,but it is insoluble in water and difficult to play a role in water-based food system.Our previous studies have confirmed that the inclusion complex of HBA with cyclodextrin(CD)can increase water solubility of HBA.In this study,hydroxypropyl-?-cyclodextrin(HP-?-CD),which is the most safe and widely used in the cyclodextrin family,it was selected as the host molecule of inclision complex and its excellent water solubility was used to improve the water solubility of HBA.Firstly,the synthesis process of hexahydro-?-acids/hydroxyl-propyl-?-cyclodextrin(HBA/HP-?-CD)inclusion complex was optimized;The bacteriostatic activity and mechanism of HBA/HP-?-CD inclusion complex were further discussed by proteomics technology;Finally,it was added to the grape juice,and its application in fresh juice was evaluated to explore its preservation effect,in order to provide a reference for its applications in the food industry.Based on the above research,the main works of this paper are as follow:(1)The HBA/HP-?-CD inclusion complex was prepared by grinding method,the effects of the weight ratio of host and guest molecular,grinding temperature and time on the inclusion rate were investigated.The response surface methodology was used to investigate the effects of the three factors and their interactions.The optimal conditions were determined as follows:grinding temperature is 25oC;The grinding time is 100 min;The molecular weight ratio of host to guest:M(HBA):M(HP-?-CD)=1:63.The solubility of HBA/HP-?-CD inclusion complex in water was tested,and it was found that the solubility of HBA in water was up to 5.89 mg/m L,which means that the solubility of the HBA in water increased drastically after formation of HBA/HP-?-CD inclusion complex.(2)The results of bacteriostasis experiment showed that HBA/HP-?-CD inclusion complex had no inhibitory activity against Salmonella paratyphi B CMCC(B)50094,and the best inhibitory activity was discovered on HBA/HP-?-CD inclusion complex against Listeria monocytogenes ATCC19115.The minimal inhibitory concentration (MIC)and minimal bactericidal concentration(MBC)of HBA against Listeria monocytogenes were 0.025 mg/m L and 0.100 mg/m L,respectively.The growth curve of Listeria monocytogenes showed that the HBA/HP-?-CD inclusion complex significantly inhibited the growth and reproduction of Listeria monocytogenes.SEM characterization and conductivity experiments preliminarily verified that HBA/HP-?-CD inclusion complex can destroy the cell membrane of Listeria monocytogenes,and obvious folds,collapses and even breakage of the cell membrane of Listeria monocytogenes can be clearly seen from the SEM images electron microscope.(3)In order to further understand the inhibitory mechanism of HBA/HP-?-CD inclusion complex on Listeria monocytogenes,proteomic methods were used to study the protein expression in Listeria monocytogenes cells treated with HBA/HP-?-CD inclusion complex.The results of bioinformatics analysis showed that HBA/HP-?-CD inclusion complex could destroy the cell wall and cell membrane of Listeria monocytogenes,resulting in electrolyte imbalance and increasing of reactive oxygen species(ROS).By inhibiting the expression of proteins related to DNA replication,transcription,translation and ribosome synthesis,the protein content in Listeria monocytogenes cells is reduced,and normal life activities can not be carried out normally;By disrupting the energy uptake mechanism of Listeria monocytogenes,the bacterial cells can not obtain enough energy,and eventually lead to bacterial death.(4)Based on the antibacterial activity and antibacterial mechanism of HBA/HP-?-CD inclusion complex,HBA/HP-?-CD inclusion complex was used in fresh grape juice,and its antiseptic effect in water-based food system was observed.The HBA/HP-?-CD inclusion complex with the concentration of 0.25 and 0.5 g/kg were added into grape juice,and the preservation effect was investigated by measuring the indexes of vitamin C,DPPH radical scavenging activity,polyphenol content,anthocyanin content,glucose content,fructose content and total bacteria count of grape juice.The main conclusions are as follow:HBA/HP-?-CD inclusion complex played a better role than potassium sorbate in maintaining vitamin C content,polyphenol content and anthocyanin content.Because HBA/HP-?-CD inclusion complex itself had antioxidant capacity,the DPPH free radical scavenging capacity of grape juice was higher than potassium sorbate group and blank control group.The total bacterial count experiment showed that the bacteriostatic ability of potassium sorbate was stronger than that of HBA/HP-?-CD inclusion complex. |
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