| Octyl gallate(OG),as one of alkyl derivatives of gallic acid that is a natural phenolic acid,has been approved by the Food and Drug Administration(FDA),the Food and Drug Organization of the United Nations(FAO)and the World Health Organization(WHO)as a grease or oil-rich food additive.It can effectively prevent the harmful alternations of oxidizing nutrients and prolong the food shelf-life.Meanwhile,it can prevent oxidative damage and help to prevent cardiovascular,neurological and cancer diseases.Although the bacteriostatic activity of OG has been paid more and more attention in recent years,there are few reports on its antibacterial mechanism against some foodborne pathogens.In addition,due to the hydrophobicity of fatty acid chain in octyl gallate molecule,its water solubility is low and almost insoluble in water,which limits its application in food,cosmetics and pharmacy.Cyclodextrin can form a water-soluble entrapment of fat-soluble insoluble substances because of its hydrophilic outer surface and a lipophilic central cavity.Especially in the field of food,it has been used as a food additive for many purposes.Therefore,this study selected cyclodextrin encapsulation method to maintain or improve the functional characteristics of OG,enhance water solubility and expand its application range.Firstly,through the analysis of the geometric compatibility of the main cavity and the object and the structure of the object,?-cyclodextrin(?-CD)and hydroxypropyl-?-cyclodextrin(HP-?-CD)were applied to encapsulate OG.It was found that the entrapment efficiency of?-CD to OG was 98%,the solubility in water was increased,and the antibacterial activity was obviously improved.?-cyclodextrin/octyl gallate inclusion complexes(?-CD/OG-IC)was prepared by?-CD and its structural characteristics were determined by Fourier transform infrared spectroscopy(FT-IR),Differential Scanning Calorimetry(DSC),X-ray diffraction(XRD),Nuclear magnetic resonance(~1H-NMR),Scanning electron microscope(SEM).Secondly,the antimicrobial activity of?-CD/OG-IC against Staphylococcus aureus ATCC 6538,Listeria monocytogenes ATCC 19115 and Escherichia coli ATCC 25922,Pseudomonas fluorescens was measured by minimum inhibitory concentration(MIC),minimum bactericidal concentration(MBC)and growth curve.It was found that the antimicrobial activity of?-CD/OG-IC against Gram-positive bacteria was higher than that of Gram-negative bacteria.At the same time,the antimicrobial mechanism of?-CD/OG-IC was studied through the integrity and permeability of the bacterial membrane,the change of membrane surface potential and the binding mode with DNA.It is found that?-CD/OG-IC can change the permeability and integrity of bacterial cell membrane and lead to the leakage of cell contents(such as protein,nucleic acid,etc.).?-CD/OG-IC can also produce intercalative binding mode with base pairs stacked parallel to genetic material DNA,which leads to the change of molecular structure and function of DNA to a certain extent.Then,the edible chitosan membrane with?-CD/OG-IC was prepared(CS-?-CD/OG-IC).It was found that the physicochemical properties such as bacteriostatic activity,UV barrier and steam barrier were improved after the addition of?-CD/OG-IC,which was more in line with the requirements of food packaging.In order to expand the application of CS-?-CD/OG-IC,nanofiber materials were prepared by electrospinning.Finally,CS-?-CD/OG-IC was applied to the preservation of blueberries and Sturgeon by a coating method.During 4 ~oC cold storage,the decay rate,weight loss rate and soluble solids of blueberry,as well as the changes of total viable counts and flavor of Sturgeon were measured.It was found that CS-?-CD/OG-IC could delay the decay process and prolong the storage period.This is of great significance for the application of CS-?-CD/OG-IC in the preservation of fruits,vegetables and aquatic products. |
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