The Preparation And Characterization Of Eugenol Loaded Chitosan Emulsions And Their Preservation Effect On Hairtail Meat During Cold Storage

The study aims to fabricate eugenol-loaded chitosan emulsion as a natural fresh-keeping material in food industry.The effect of Tween20 content(0-0.54 g),chitosan-eugenol weight ratio(1:0.8-1:1.4,w/w),ultrasonication power(0-750 W)and time(0-15 min)on the synthesis of emusion was systematically investigated to obtain lower droplet diameter with greater stability and encapsulation efficiency(EE).The physicochemical properties,antioxidant properties and antibacterial activity were assayed by Fourier transform infrared(FTIR)spectroscopy,thermogravimetry(TG),derivative thermogravimetry(DTG),X-ray diffraction(XRD),and scanning electron microscopy(SEM),etc.The preservation effect of eugenol-loaded chitosan nano-preparation on hairtail quality properties during cold storage was studied.Physical,chemical and microbial properties in combination with sensory evaluation were included.Differential proteomics was analyzed via 2-DE and MALDI-TOF/TOF techniques to further study how eugenol-loaded chitosan nano-preparation prolonged the shelf life of 4℃-stored hairtail in terms of protein denaturation and degradation meanwhile the preservation mechanism was preliminarily revealed.In a whole,this study provided theoretical basis for a wide application of eugenol-loaded chitosan emulsion as a natural fresh-keeping material in fishery fields.The main results were as follows:1.The droplet size and encapsulation efficiency(EE)were determined to evaluate the effect of testing factors on the eugenol-loaded chitosan emulsions.The optimized parameters with chitosan/eugenol weight ratio of 1:1 and 0.36 g of Tween20 at the ultrasonic treatment at 450 W at 6 min were selected for the preparation of the emusions.2.SEM analysis confirmed the formation of regularly distributed spherical nanoparticles with in the size range no more than 100 nm.XRD,FTIR,TG and DTG analysis indicated that eugenol was encapsulated into chitosan nanoparticles and its thermal stability was enhanced.The eugenol-loaded chitosan emulsions showed great storage stability and thermal stability while the nano-preparation exhibited excellent antioxidant capacity,controllable release as well as antimicrobial activity,and their MIC against Staphylococcus aureus,Escherichia coli,Pseudomonas aeruginosa and Salmonella was approximate 195.31,97.66,195.31 and 390.63 μg/mL,respectively.The antibacterial activity of eugenol-loaded chitosan nano-preparation was significantly(P<0.05)higher than that of free eugenol,suggesting that antibacterial activity was significantly(P<0.05)enhanced during the emulsification and encapsulation process.3.The total bacteria count,pH value,conductivity,water holding capacity(WHC),TBA value,TVB-N value,and texture of hairtail meat were determined during its cold storage,with sensory evaluation.The results showed that pH value firstly decreased then increased,while conductivity firstly increased then decreased and finally tended towards stability.WHC decreased with the storage time extended.The total bacteria count increased,and eugenol-loaded chitosan nano-preparation had significant antibacterial activity(P<0.05).TBA and TVB-N value were all increasing with the storage time,and eugenol-loaded chitosan nano-preparation group exhibited lower rising speed than that of the control group,indicating the excellent capacity of lipid oxidation and protein degradation.Texture quality was almost decreasing,including hardness,gumminess,and chewiness,the change of which was delayed by eugenol-loaded chitosan nano-preparation.The results of sensory evaluation were in accordance with those of physical,chemical and microbial indexes and the quality of hairtail was as follows:eugenol-loaded chitosan nano-preparation group>chitosan-TPP particles group>control group.4.In the SDS-PAGE experiment,when the refrigerating time was extended to 18 d,there was a significant difference of protein bands between the control and the treated samples,especially actin(44.3 kD),tropomyosin(37 kD)and myogenic protein(33 kD).The lightening of these protein bands may be attributed to the degradation and denaturation of macromolecular proteins,and the lightening of protein bands of the control is more obvious,indicating that eugenol-loaded chitosan nano-preparation could protect the hairtail protein denaturation.With the prolongation of refrigerating time,the differential protein amount of eugenol-loaded chitosan nano-preparation group was less than that of the control group,suggesting that eugenol-loaded chitosan nano-preparation could protect the hairtail protein denaturation.In addition,the cellular composition and molecular function in which differential proteins were mainly involved were also found.