Preparation And Characterization Of Rabbit Skin Gelatin Films Incorporated With Rosemary Acid

With the increasing demand for food safety and food packaging,food active packaging materials made by natural polymeric have drawn much attention.In this study,gelatin/RosA composite film was prepared by using rabbit skin gelatin as film matrix and combining the antioxidant properties of rosemary acid(RosA).First of all,we investigated the effect of RosA on rabbit gelatin gel system,and then carried out a series of experiments on the functional properties,microstructure,antioxidant activity,release of RosA from the film and its application in food.The effect of different concentrations of RosA on rabbit gelatin gel systems showed that RosA could quench the fluorescence of gelatin,and it was a static quenching process with the formation of complex substance.When RosA additions was 0.08%,the gel strength was not significantly increased(P>0.05),With the increasing concentrations of RosA,the gel strength was increased significantly(P<0.05);rheological results showed that the addition of RosA could increase the storage modulus G ' and loss modulus G' of gelatin,but did not significantly affect the gelatinization and melting temperatures of the gelatin samples.This showed that RosA was not involved in the formation of tri-helical structures of gelatin during the formation of gels and sols.The subunit components results showed that the interaction between RosA and gelatin were mainly non-covalent bonds,RosA did not lead the degradation or aggregation of gelatin protein.Circular dichroism showed that the addition of RosA resulted in the peptide structure of gelatin was partially unfolded with decreasing in ?-helix and increasing in ?-sheet.The influence of RosA on the properties and structure of rabbit skin gelatin film was investigated in this paper.When the RosA concentration was ?0.05%,the mechanical properties of the composite film were significantly improved(P<0.05).However,when the RosA concentration was increased to 0.08%,the elongation at break(EAB)of the film decreased,and the tensile strength(TS)was significantly increased(P<0.05)compared with the controls.In addition,the addition of RosA increased the thickness and improved the water resistance and UV barrier properties of gelatin films,but decreased the transparency.Fourier transform infrared spectroscopy(FT-IR)showed that hydrogen bonds were formed between the carboxyl and phenolic hydroxyl groups on the benzene ring of RosA and the NH group of the side chain of gelatin.As the concentration of RosA increased,part of the gelatin structure unfolded and formed a more compact film network structure.The network structure of the film made the thermal stability of films increase and a more obvious layer appeared on cross-sections of films.The antioxidant activity of the composite film and the release of RosA in the film matrix were measured,it was found that with increasing concentrations of RosA,the antioxidant activity of the films was also significantly increased(P<0.05).The polarity of the solution could affect the release of RosA in the composite film,and a moderately polar environment was more beneficial to the release of RosA.In addition,the increase in temperature could accelerate the release of RosA from composite film.In order to explore the application of the composite films,the gelatin films incorporated with RosA were used to evaluate the freshness of pork and observe the quality changes of bacon.The study on the quality changes of the freshness of pork during storage showed that the shelf life of 0.08% RosA gelatin film and poly Ethylene(PE)/0.08% RosA gelatin film treatment group was extended for 2d and 4d,respectively,compared with the control group.It showed that the gelatin film incorporated with RosA could extend the shelf life of pork with delaying the deterioration of pork spoilage,and when the outer was sealed with PE,the refrigerated effect was better.At the same time,the color,hardness and other measurements found that the pork wrapped with PE/RosA gelatin film had better color and hardness.This showed that PE/RosA gelatin film can be used as a new type of active packaging for chilled pork.The study on the quality changes of bacon during storage showed that compared with the control group,the gelatin films incorporated with RosA treatment groups had lower peroxide value(POV),thiobarbituric acid value(TBARS)and acid value(AV)with the extension of storage time.This showed that the addition of RosA could improve the antioxidant activity of the gelatin film and retarded the lipid oxidation of bacon,and the higher the RosA concentration,the better the effect of inhibiting lipid peroxidation.