Preparation And Characterization Of Cinnamaldehyde/Fish Skin Collagen Film With Antimicrobial Activity And Its Mechanism Of Grass Carp Fillets Preservation

Collagen is a commonly used edible film matrix material and has been widely used in food packaging for its biodegradable and good film-forming properties.In combination with various natural active substances,such as tea polyphenols,curcumin,and cinnamon essential oil,it can impart antioxidant activity and/or antimicrobial activity to the collagen film.Cinnamaldehyde,the main component of cinnamon essential oil,is a natural active substance.It has strong antibacterial activity and is listed as“Generally Recognized as Safe-GRAS”by the US Food and Drug Administration.However,cinnamaldehyde is unstable and has low solubility.In this study,the cinnamaldehyde/sulfobutyl-beta-cyclodextrin(CA-SBE-?-CD)inclusion complex was prepared by using sulfobutyl beta-cyclodextrin to encapsulate the natural antimicrobial agent cinnamaldehyde,and then the cinnamaldehyde inclusion solution and cinnamaldehyde emulsion were combined with collagen from squid skin to form composite film with antibacterial activity.Finally,the preservation mechanism of collagen active coatings on grass carp fillets was studied by coating method.The detailed research contents are as follows:(1)The inclusion system of cinnamaldehyde(CA)and sulfobutyl beta-cyclodextrin(SBE-?-CD)were created at different ratios of host to guest.The effect of guest concentration on the encapsulation efficiency was investigated.The results showed that when the concentration of cinnamaldehyde was 2 mg/m L and the concentration of SBE-?-CD was 6 mg/m L,the encapsulation efficiency was 86.34%.Meanwhile the higher the concentration of cinnamaldehyde,the lower the encapsulation efficiency.The structure of the inclusion complex was characterized by scanning electron microscopy,Fourier transform infrared spectroscopy and differential scanning calorimetry.All the results indicated that SBE-?-CD encapsulated CA successfully.(2)In this part,CA-SBE-?-CD and cinnamaldehyde emulsion were combined with gelatin(collagen extracted from silver carp skin and defined as gelatin)to prepare antibacterial composite films,whose mechanical properties,barrier properties,antibacterial properties and release rate of CA were investigated.The experimental results show that each additive can enhance the elongation at break of the film and improve the light barrier property.The bacteriostatic test showed that when the content of cinnamaldehyde in the film was 1%,the collagen composite film containing both cinnamaldehyde inclusion complex and free cinnamaldehyde had the best antibacterial activity with continued ability to inhibit the growth of bacteria.After72 hours,it remained 83.7%of its antibacterial ability.(3)With silver carp skin gelatin as matrix material,CA-SBE-?-CD and CA emulsion were added to the matrix to form coatings with antimicrobial and sustained-release properties.The preservation effect of different coatings on grass carp slices under 4°C refrigeration condition was investigated,including mass loss and p H,total volatile base nitrogen(TVB-N),fatty acid(TBA),protein degradation and microorganisms.The results demonstrated that the active coatings can reduce the mass loss,p H value and TVB-N value of fish.In the meantime,protein degradation and lipid oxidation in fish meat were both delayed.Moreover,the higher the content of CA,the better the inhibitory effect on colony growth.It was observed that the total volume of colonies of the fish samples treated with the active coatings did not exceed4 log₁₀cfu g^-1 on the 15th day,which suggests a promising way to keep the growth of microorganisms in check and effectively prolong the shelf life of the fish fillets.