| Lipid peroxidation of dry cured ham is seriously during ripening and storage process,which has greatly affected the quality of the products and the subsequent sales.Therefore,it has been a major technical problem to be solved urgently in the ham industry.At present,there are some reports on antioxidation of ham.In this lab,we have obtained some achievements in the research of antioxidation technology with film coating.Alpha tocopherol is widely used in food industry as a natural antioxidant and nutrition enhancer.However,it's easy to fast deactivation as the sensitivity to oxygen,light,metal ions and other environment factors,and it is insoluble in water,which greatly limits the scope of its application.In this paper,a new type of sustained-release antioxidant active packaging film was prepared,which was expected to be applied on the sliced ham for antioxidation coating during ripening and storage process.The release pattern of sustained-release film to the antioxidants and its antioxidant effects was discussed,and it was expected to improve the utilization rate and prolong its working time through sustained release antioxidants,which could provide theoretical basis for long-term antioxidation method of sliced ham and other dry cured meat products.1.Study on the construction,structure characterization,sustained release and antioxidant activity of chitosan encapsulated alpha tocopherol nanoparticlesIn this study,a-tocopherol has been encapsulated in chitosan nanoparticles(TOC-CSNPs)by a two-step method.The ionic gelation was happened between chitosan(CS)and sodium tripolyphosphate(TPP)in oil-in-water emulsion.To determine the optimal process,the average particle size and encapsulation efficiency were investigated as a function of chitosan concentration,?-tocopherol concentration,mass ratio of CS to TPP,pH and stirring speed by single-factor and orthogonal array designs.The CS nanoparticles were characterized by Dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FTIR)and scanning electron microscope(SEM)and evaluated for release profiles and antioxidant properties in vitro,which could provide a theoretical basis for a-tocopherol on lipid antioxidant application of cured meat products during storage.The results demonstrated that the best conditions for preparing a-tocopherol loaded chitosan nanoparticles were 1 mg/mL CS concentration,mass ratio of CS to TPP was 7:1,pH was 4.5,and the stirring speed was 900r/min.The average particle size and EE of a-tocopherol loaded nanoparticles were 214 nm and 51.65%,respectively.The FTIR spectrum confirmed the encapsulation of a-tocopherol by electrostatic adsorption,and the SEM observation showed uniform average particle size distribution and regular spherical morphology.The release curve in vitro showed that the release law was in accord with the first order kinetic model and the Higuchi model.The results of DPPH radical scavenging assay showed that the alpha tocopherol chitosan nanoparticles had good slow release and antioxidation effect.2.Study on preparation,film forming properties,sustained release antioxidation effect of chitosan based nano coating materialChitosan and montmorillonite(MMT)were used as the substrate and a-tocopherol chitosan nanoparticles were used as antioxidant carriers.The composite packaging film was prepared by solution intercalation casting film method.Effects of different MMT contents(0,5%,10%,15%,20%,CS dry weight)and different a-tocopherol chitosan nanoparticles added proportion on physicochemical properties,release properties in vitro,antioxidant effect of the composite film was studied.The effects of chitosan concentration,drying temperature and montmorillonite content on the properties of the composite films were investigated by single factor and orthogonal experiments.The structure of the composite film was characterized by Fourier transform infrared spectroscopy,X ray diffraction,and thermogravimetric analysis,scanning electron microscopy.Based on the free radical scavenging rate of DPPH,the slow release law of the composite film was evaluated,and the antioxidation effect of the film was investigated by accelerated oxidation of soybean oil.The results showed that the intercalation structure formed by the combination of 2%chitosan solution and 5%montmorillonite has good biocompatibility.The composite sustained-release film prepared by the addition of 10%a-tocopherol chitosan nanoparticles had a slow release effect on a-tocopherol,and which showed significant effect on the inhibition of soybean oil peroxidation.3.Study on the antioxidation effect of chitosan based nano coating material with sustained release antioxidation effect on sliced hamA composite sustained-release film incorporated with a-tocopherol chitosan nanoparticles was used as coating material.The dry cured sliced ham was coated with the film,vacuum packed and stored at 4? for 120 days.The effects of the active packaging with sustained-release on the antioxidant and fresh-keeping of sliced ham during the stage of ripening and storage was studied.The results showed that,compared with the traditional method of antioxidant spray and coating,the composite sustained-release film incorporated with a-tocopherol chitosan nanoparticles showed a sustained and stable antioxidant effect in 120 days of ham storage,which can effectively inhibit the peroxidation of biceps femoris muscle and subcutaneous fat and always maintain a low level of POV and TBARs values within the limits.The L*,a*and b*values of the ham were determined.It was found that the effect of composite sustained-release film treatment on delaying the decrease of a*value of ham muscle and inhibiting the subcutaneous fat yellowing was significant..The correlation between oxidation index and color value was analyzed.It was found that there was a significant negative correlation between a*value and oxidation index(p<0.01)of the biceps femoris muscle,and there was a significant positive correlation between the b*value and the oxidation index(p<0.05)of the subcutaneous fat,which could be used as an important reference for the oxidative rancidity and sensory evaluation standard of dry cured ham. |
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