Preparation Of The PBAT/PPC Composite Films Containing Mixed Acid-etched Halloysite Nanotubes/Clove Essential Oil And Study On Their Preservations Application For The Sea Bass

With the improvement of people’s living standard,people’s demand for fresh aquatic products is increasing,and the aquatic products breeding,processing,transportation and preservation industries are developing rapidly.But the aquatic products are rich in protein and fat,which are extremely easy to breed bacteria and water loss and protein degradation occur.In order to better meet the demand of preservation of aquatic products,most of the aquatic products are packed with active antimicrobial materials,especially the packaging materials based on degradable materials,which have excellent biodegradability,have become substitutes to many traditional plastics.Therefore,poly(butylene adipate-co-terephthalate)(PBAT)and poly(propylene carbonate)(PPC)were used as film-forming substrates in this study,the effects of different blending ratios of PBAT and PPC on the properties of PBAT/PPC composite films were studied,and the films with good comprehensive properties were selected.Finally,the films were applied to sea bass packaging to study the effect of the films on sea bass preservation.Firstly,PBAT was used as the substrate of films,the influence of different blend ratio of PBAT and PPC on the properties of PBAT/PPC composite films was studied.The results showed that the luminance of the films increased with the addition of PPC,and the films showed a slight red-yellow trend.The results of SEM showed that the surfaces of the films wrer smooth.The number and size of particles in the dispersed phase increased gradually,and the cross section becomed rough with the addition of PPC.With the increase of PPC content,the tensile strength decreased slightly,the elongation at break decreased significantly(p < 0.05),and the elastic modulus increased significantly(p < 0.05),the results showed that the strength and ductility of the films decreased with the increase of PPC content,while the stiffness of the films increased.The addition of PPC improved the gas barrier performance of the film,the permeability of oxygen and water vapor decreased,which may be due to the fact that PPC material had a greater effect on the gas diffusion than PBAT material when the gas diffused through the film,the gas barrier property of PBAT blend film was improved.The FTIR spectra showed that the absorption peak of C-O in the crystalline region and C=O in the amorphous region of PBAT weakend with the addition of PPC,which was related to the hydrogen bonding force in the PBAT matrix.The addition of PPC weakened the hydrogen bonding force in PBAT matrix.When the content of PPC reached 30%,PPC breaked the continuous phase and force of the matrix,and replaced some of the hydrogen bonds formed by PBAT.The number of hydrogen bonds among PBAT molecules decreased,and the number of hydrogen bonds between PPC and PBAT increased.On the basis of the above research,PBAT/PPC(7:3)was selected as the films material,and the effect of clove essential oil or the mixed acid-etched halloysite nanotubes/clove essential oil on the properties of PBAT/PPC composite films were studied.Firstly,the HNTs was etched with acid,the mixed acid-etched halloysite nanotubes/clove essential oil was obtained by mixing and loading clove essential oil with acid etched HNTs.The addition of clove essential oil and the mixed acid-etched halloysite nanotubes/clove essential oil made the films appear yellow-green,the transparence and gas barrier of the films were decreased,and the fims were highly resistant to E.coli,Staphylococcus auteus and shivella spoilage.The tensile strength and gas barrier property of the films containing HNTs/clove essential oil increased compared with that containing clove essential oil.At the same time,HNTs promoted the dispersion of clove essential oil in the film and slowed down the release of clove essential oil.Therefore,the mixed acid-etched halloysite nanotubes/clove essential oil gave PBAT/PPC films a good antibacterial activity and a sustained-release effect on clove oil in the films.Finally,three kinds of films,PBAT/PPC(without clove essential oil),PBAT/PPC/clove(with clove essential oil)and PBAT/PPC/HNTs-4M-clove(with the mixed acid-etched halloysite nanotubes/clove essential oil),were used in the packaging of sea bass.The effects of films on storage and preservation of sea bass were studied.The indexes indicating the freshness of sea bass were determined.The results of sensory evaluation showed that the sensory scores of each group were decreased in different degrees,and the sensory scores of each group was: PBAT/PPC <PBAT/PPC/clove < PBAT/PPC/HNTs-4M-clove.The results showed that the sea bass packed with clove essential oil had better sensory quality.The results of sea bass flesh color showed that L*,a*,b* and color difference values of each group gradually increased.The overall performance of the brightness of fish was getting higher and higher,the color of sea bass flesh showed red-yellow trend.The changes of color and color difference of sea bass flesh of the films containing clove essential oil were smaller than PBAT/PPC group.The texture results showed that the hardness,adhesiveness,elasticity and cohesiveness of all groups decreased with the prolongation of storage time,the hardness,adhesion and elasticity of sea bass flesh of the films containing clove essential oil were higher than PBAT/PPC group.PBAT/PPC/HNTs-4M-clove film had the best retention effect on hardness,adhesiveness and elasticity of sea bass flesh,which was related to the sustained-release effect of the film.The results of water distribution showed that the trend of water proportion of sea bass flesh in each group was the decrease of free water proportion,which indicated that the water holding capacity of fish decreased in different degrees,the water-holding effect of sea bass flesh treated with the films containing clove essential oil was better.The volatile base total nitrogen and total number of colonies of sea bass flesh in each group increased to different degrees,TVB-N value: PBAT/PPC>PBAT/PPC/clove>PBAT/PPC/HNTs-4M-clove;Total number of colonies:PBAT/PPC>PBAT/PPC/clove>PBAT/PPC/HNTs-4M-clove,indicated that the films containing clove essential oil effectively inhibited the increase of TVB-N and total number of colonies.The p H value of sea bass flesh in all treatment groups decreased first and then increased.The p H value:PBAT/PPC>PBAT/PPC/clove >PBAT/PPC/HNTs-4M-clove,indicated that the films containing clove essential oil effectively inhibited the increase of p H value,PBAT/PPC/HNTs-4M-clove had the best effect in inhibiting the increase of p H value of sea bass flesh.