| With increasing concerns on environmental protection and food packaging safety,clearly edible films become an important area of food research with enormous commercial potential and great significance to the environment,Currently,developing green,safe and biodegradable active edible films by using natural renewable and biodegradable materials as base material adding functional additives,such as antioxidants,antibacterial agents,is a trend in food packaging and preservation field.In this study,chitosan(CS),sodium carboxymethyl cellulose(CMC)and phlorotannins were used as raw materials to prepare chitosan-based phlorotannins edible films,and the properties related to food packaging of the edible films were characterized.Phlorotannins is an extract and can be added directly to the film-forming solution to prepare edible films with antibacterial and antioxidative effects.During the preparation and use of edible films,the phlorotannins are sensitive to oxygen,light and other environmental factors,may be oxidized to varying degrees,resulting in a decrease of antioxidative properties.Therefore we investigated the preparation of nanoparticles to encapsulate polyphenols by ionotropic gelation,analyze effects ofdifferent factors on characteristics of nanoparticles.Nanoparticles were added to the the film-forming solution to prepare nano-phlorotannins edible films fluid to in order to improve the antioxidant activities antibacterial properties of edible films.Finally,edible films were applied to Scophthalmus maximus during refrigerated storage.The effects of edible film on the shelf life of fish fillets were investigated by measuring sensory indicators,physical and chemical indicators and microbiological indicators of refrigerated fish fillets..The results of this study could provide basic data and technical support for developing chitosan based active food packagings.The main contents and results of this study were as follows:Preparation and optimization technology of chitosan based phlorotannins edible films.Using chitosan and CMC as film materials,the edible films were prepared by casting method.By comparing basic physical properties of the edible films prepared under different conditions,it was determined that suitable drying temperature was 50 ℃.and drying time was 5 h,glycerol was used as plasticizer.The preparation conditions for edible film using CMC and chitosan as film material were optimized,The optimal preparation conditions of edible films of of chitosan based phlorotannins edible films were determined with tensile strength,elongation at break and water vapor permeability as the evaluation indexes.by multi-index comprehensive scoring combined with orthogonal test.The optimal process conditions were as follows: chitosan concentration 1.5%,glycerol concentration 1.0%,phlorotannins concentration 0.4 % and CMC concentration 2.0%.Under the above optimum conditions,the edible films showed better physical properties,comprehensive score were 69.06.There were good compatibilities between components of the prepared composite edible film.The film surface was smooth,dense and porose.Analysis of influencing factors for the preparation of phlorotannins nanoparticles by ionotropic gelation.We prepared phlorotannins nanoparticles by ionotropic gelation.characteristics.of nanoparticles were characterized by Laser particle size analyzer and transmission electron microscopy(TEM).Effects of chitosan concentration,initial pH value of CS solution and CS-TPP mass ratio on characteristics of nanoparticles were studied.And encapsulation effects and release behavior of nanoparticles were evaluated.The results showed that,with the increase of chitosan concentration,the particle size and Zeta potential of nanoparticles increased significantly;When initial pH value of CS solution in the range of 3.5~5.0,The particle size of nanoparticles is relatively uniform and the potential is relatively stable.When the mass ratio of CS-TPP is ≥5.0,the particle size of the nanoparticles is small,and the potential tends to be stable.When chitosan concentration was 1 mg/ml initial pH of the chitosan solution was 5.0,CS-TPP mass ratio was 5:1,the nanoparticles which the average particle size was about 152 nm could be obtained.The prepared nanoparticles are stable and have a good dispersibility.The prepared phlorotannins nanoparticles had a certain encapsulation effect.Nanoparticles had loading efficiency(LE)between 28.29~42.50% and loading capacity(LC)between10.88~35.42;Meanwhile,in vitro release study indicated that burst release of phlorotannins occurred in the first 4 h of nanoparticles.The prepared nanoparticles had certain sustained-release properties.Determination of properties of chitosan-based nano-phlorotannins edible films.0.4% nano-phlorotannins were added to the film-forming solution to prepare chitosanbased nano-phlorotannins edible films with antibacterial and antioxidative effects.Basic physical properties of the edible films were compared.The antibacterial properties and antioxidant activities of the edible film were investigated by the inhibition zone test and DPPH radical scavenging capacity experiments.Compared with the edible films prepared with direct addition of phlorotannins,chitosan-based nano-phlorotannins edible films showed no significant differences in basic physical properties(P>0.05),except for increased transparency.The results showed that prepared edible films exhibited good inhibitory effects on Escherichia coli and Staphylococcus aureus.The inhibitory effect of chitosan-based nano-phlorotannins edible films were higher than that of chitosan-based phlorotannins edible films.Diameters of inhibition zone of chitosan-based nanophlorotannins edible films on Escherichia coli and Staphylococcus aureus were11.05±0.32 mm and 8.04±0.36 mm.The antioxidant activities of the edible films increased significantly with increasing of phlorotannins concentration,DPPH radical scavenging rate of chitosan-based phlorotannins edible films and chitosan-based nano-phlorotannins edible films were 47.93% and 52.60%,indicating that antioxidant activities of latter were higher than that of former.Applications of edible films on Scophthalmus maximus during refrigerated storage.Fresh-keeping effectiveness of PE packaging,chitosan-based phlorotannins edible films + PE packaging and chitosan-based nano-phlorotannins edible films on refrigerated Scophthalmus maximus fillets were investigated.The sensory score,drop loss,pH value,total volatile basis nitrogen(TVB-N)value,thiobarbituric acid(TBA)value and total plate count were tracked and analyzed to evaluate the quality effectiveness of Scophthalmus maximus fillets during refrigerated storage.The results showed that with the prolonged storage time,drop loss,TVB-N value and total plate count of Scophthalmus maximus fillets increased,which were consistented with the results of sensory evaluation.The pH value and TBA value which is packed in two edible films was lower than that of the control group..On the 15 th day,the TVB-N values were 33.43,29.03,and 25.53 mg N/100 g respectively,the TBA values were 1.41,1.23,and 1.13 mg MDA/kg respectively,The and total plate count were 7.07,6.41,and 5.97 lg(CFU/g)respectively.Chitosan-based nano-phlorotannins edible films and chitosan-based phlorotannins edible films used to refrigerated Scophthalmus maximus fillets can extend the shelf life about 2 d and 3 d respectively.The preservative effectiveness of three kinds of packaging treatments follows the order: chitosan-based nano-phlorotannins edible films + PE Packaging> chitosan-based phlorotannins edible films + PE packaging> PE packaging. |
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