| Keeping fresh for fresh produce,especially seafood products have been paid attention for many years in the industry during the cold chain preservation period.Controlling the corruption process caused by the microorganism breeding and oxidation is one of the key factors to ensure the quality of seafood.And using active packaging film is a kind of effective way to implement the packaging for seafood.Active packaging is a packaging technology which uses packaging materials as the carrier and controls the release of antimicrobial or antioxidant compounds from films into the food surface to inhibit the reproduction of microorganisms or prevent the oxidant of fat and slow down the corruption of food.This subject takes polylactic acid?PLA?and poly?butylene succinate adipate??PBSA?as base material,8%carvacrol,8%thymol,4%carvacrol+4%thymol as functional compounds to prepare kinds of packaging films with the function of antimicrobial antioxidant by extrusion-casting method.The effect of carvacrol and thymol incorporation on functional properties of packaging films,the release of functional compounds through films in different food simulants and the correlation between release process in salmon slice and preservation of salmon slice were investigated.The main research contents and research conclusions were as follows:?1?The active PLA-PBSA packaging films with carvacrol and thymol were prepared by extrusion-casting method.The physical,mechanical,antimicrobial,antioxidant and thermal performance of films were measured.The results showed that,the microstructure and chemical structure of PLA-PBSA films were not affected by carvacrol and thymol,which had a good compatibility with PLA-PBSA material.The addition of carvacrol and thymol reduced the crystallinity of PLA-PBSA films and greatly improved the flexibility and transparency,enhanced the antibacterial and antioxidant properties of films.?2?The release of carvacrol and thymol from active PLA-PBSA films into simulants and actual food was evaluated and the method was developed for determining carvacrol and thymol by High Performance Liquid Chromatography?HPLC?to research the release mechanism of functional agents in different simulants and the release regularity in actual solid food?salmon slice?.The results showed that,the mechanisms involved in release process of carvacrol and thymol through PLA-PBSA based films contact with water,3%acetic acid,10%ethanol and 95%ethanol simulants were in keeping with Fick's diffusion,and the release values?V?of active agents obtained under similar temperature and time was in the following order:V 95%ethanol>V 3%acetic acid>V 10%ethanol>V water.Moreover,the amount of release for carvacrol and thymol migrated to real food was twice that of release concentration in water simulant and only 1.6%of the the maximum concentration in 95%ethanol simulant.?3?The active PLA-PBSA films were applied in preservation of salmon slice during cold storage.The total viable counts?TVC?,thiobarbituric acid reactive substances?TBARS?,total volatile base nitrogen?TVB-N?,pH,color and texture properties were analyzed periodically to evaluate the effect of PLA-PBSA films in salmon slice and investigated the correlation between release process and preservation of salmon slice.The results showed that,the release rate and concentration of carvacrol and thymol in salmon slice were lower than in food simulants,which was between the release concentration in water simulant and 95%ethanol simulant,but the effect of active PLA-PBSA packaging films on actual preservation of salmon slice were still remarkable.The control salmon slice samples packaged in pure PLA-PBSA film was spolied after the 5th day of storage,while the treatment groups?group B,C and D?showed better quality until the 8th or even 9th day of storage at?4±1??.It indicated that release of active agents with volatility property may have postive effect on the preservation of salmon slice,and extended the preservation of salmon slice for3-4 days during cold storage. |
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