| Chilled pork is more and more popular with the consumers in the world due to its taste and nutrition,and chilled pork as an alternative for traditional hot meat and refrigerated meat is an important trend of meat consumption.However,chilled pork only has a short shelf-life of few days,which is attributed to the quick growth of some psychrophilic microorganisms despite stored at low temperature(0～4℃).Essential oils are ideal agents used for meat preservation due to excellent antibacterial property and safety nature,but low-water solubility,volatility and strong flavor they possess also limit their application in food.In this study,emulsions containing cinnamon oil was prepared by using hydroxypropylmethyl cellulose(HPMC)as emulsifier and the physicochemical properties and antibacterial activity of emulisons were studied.The the emulsion coatings were applied to chilled pork preservation,in order to provide reference for the application of essential oil emulsion in food especially chilled meat preservation.Firstly,cinnamon oil-HPMC emuslions were prepared by two different methods and the effect of preparation methods and HPMC concentration(0.05-1wt%)on emulsion characterization was evaluated.Common emulsion made by high speed blender resulted in larger droplet,with droplet size higher than 1 μm.While the emulsion made by high pressure homogenization resulted in submicro particles with the smallest droplet size around 158 nm.Compared with common emulsions,submicro emulsions had more homogeneous droplet distribution and higher stability.All emulsions exhibited shear-thinning properties,and the storage modulus(G’)was larger than their loss modulus(G")at low frequency,indicating all samples displayed as solid-like viscoelastic matter.With the increasing concentration of HPMC,emulsion viscosity and stability increased while droplet size decreased.Following it,the antibacterial properties of 1wt%HPMC common emulsion,1wt%HPMC submicro emusion and oil-water dispersion were studied.The inhibition zone assay indicated the three antibacterial had different degrees of inhibition on the selected test bacteria including S.aureus,E.coli.,L.monocytogenes,and S.enteritidis.Submicro emulsion presented the highest antibacterial ability with the largest inhibition zone diameters:3.43±0.10 cm,3.05±0.25 cm,3.29±0.11 cm,2.37±0.25 cm respectively.According to the minimum inhibitory concentration(MIC)assay and scanning electron microscopy(SEM),these three antibacterials had better inhibitory effect on S.aureus.Besides,the antibacterial ability of oil-water dispersion,common emulsion and submicro emulsion enhanced successively.Finally,the influence of oil-water dispersion,common emulsion and submicro emulsion coatings on the quality of chilled pork was investigated.After 12 days storage,the samples coated with submicro emulsion,common emulsion and oil-water dispersion were 2.76,2.17,1.08 log CFU/g lower than the control,respectively.The total volatile base nitrogen(TVB-N)values of the three groups were 13.5 mg/100 g,8.5 mg/100 g,5.3 mg/100 g lower than the control,respectively.Compared with the control,these three groups had lower weight loss,pH values(p<0.05)and higher sensory scores.Among them,submicro emulsion got the best preservation effect.In summary,emulsions preparaed by high speed blender and high pressure homogenization using HPMC as emulsifier showed higher antibacterial properties.Good results were obtained when emulsions were used for fresh preservation of chilled pork.The potential application value of cinnamon essential oil-HPMC emulsions in food preservation was initially shown. |
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