| Chilled pork is rich in nutrition and delicious taste,which is favored by people.However,chilled pork is susceptible to microbial contamination and deteriorates,resulting in shortened shelf life,which limits its development.Therefore,it is of great significance to develop new preservation methods to extend the shelf life of chilled pork.Natural preservative cinnamon essential oil(CEO)has a broad spectrum of antibacterial and antioxidant effects,but cinnamon essential oil is volatile and sensitive to light and heat,and its effects will be greatly reduced if applied directly.Therefore,in this study,cinnamon essential oil liposomes(CEO-Lip)were by embedding cinnamon essential oil with thin film dispersion and high pressure homogenization method,and sodium alginate-chitosan modified cinnamon essential oil liposomes(SA-CH-CEO-Lip)were prepared by layer-by-layer electrostatic method,and then applied to the preservation of chilled pork.During storage,the effects of sodium alginate and chitosan modified cinnamon essential oil liposomes on the quality of chilled pork were evaluated through physicochemical properties and sensory evaluation,and the extension degree the shelf life of chilled pork was explored,aiming to provide technical reference and theoretical basis for the application of essential oil liposomes in food preservation.The main research results are as follows:(1)CEO-Lip were prepared by thin film dispersion and high pressure homogenization method.Using average particle size and embedding rate as indexes,the three factors that had the greatest influence on CEO-Lip were determined by single factor test.Based on this,response surface test was used to optimize the preparation process.The single factor test showed that the three factors that affected CEO-Lip most were the mass ratio of phospholipid to cholesterol,the concentration of cinnamon essential oil and the concentration of tween 80.Response surface test results showed that the optimal preparation technology was as follows:mass ratio of phospholipid to cholesterol 4.09:1,concentration of cinnamon essential oil 2.46mg/m L,concentration of tween 80 2.99 mg/m L.Under these conditions,the embedding rate was 81.95%,which fits well with the theoretical value,and can provide reference for the production and application of CEO-Lip.(2)The cinnamon essential oil liposomes prepared under the best conditions were characterized.The results of transmission electron microscopy(TEM)showed that the cinnamon essential oil liposomes were a single layer vesicle with particle size of 94.21 nm,the polydispersion index(PDI)of 0.133,Zeta potential of-40.4 m V,and the emulsion had good stability.Fourier transform infrared spectroscopy(FTIR)analysis showed that hydrogen bond was formed between cinnamon essential oil and non-polar head in liposomes,indicating that cinnamon essential oil was successfully embedded.In vitro release test,the cumulative release rate of CEO was 79.23% at 24 h,which was consistent with the first-order kinetic model,and confirmed that the liposomes had a sustained release effect on cinnamon essential oil.Compared with CEO,CEO-Lip showed better antibacterial activity against Escherichia coli and Staphylococcus aureus on the 4th day,indicating that CEO-Lip had long-term antibacterial effect.GC-MS analysis showed that there were differences in the relative components of cinnamon essential oil and CEO-Lip,but there were no significant differences in the types of key components.(3)Chitosan(CH)modified CEO-Lip(CH-CEO-Lip),sodium alginate(SA)and CH double modified CEO-Lip(SA-CH-CEO-Lip)were prepared by electrostatically self-assembled layer-by-layer deposition,and the effects of the modification on their physicochemical properties were evaluated.The results showed that the particle sizes of CEO-Lip,CH-CEO-Lip and SA-CH-CEO-Lip increased successively,and were 91.39 nm,119.67 nm and 178.73 nm with regular vesicle structure,respectively.The embedding rate of SA-CH-CEO-Lip was the highest 89.50%.FTIR and differential scanning calorimeter(DSC)analysis confirmed that CH and SA were successfully coated on the liposome surface.SA-CH-CEO-Lip showed the best stability when stored at 4℃ for 18 d.Compared with CEO-Lip,the antioxidant activity of SA-CH-CEO-Lip increased from 44.70% to 70.50%,and could inhibit bacterial growth,showing good antibacterial and antioxidant activities.In vitro release results showed that the cumulative release rate of CEO in SA-CH-CEO-Lip(71.42%)was significantly lower than that of CEO-Lip(81.24%)at 72 h,indicating that the protective layer formed after double-layer modification has a certain slow release effect on the core material of liposomes.(4)In order to explore the applicability of complex liposomes,SA-CH-CEO-Lip were applied to the preservation of chilled pork.The p H value,weight loss rate,total bacteria count(TBC),total volatile basic nitrogen(TVB-N),thiobarbituric acid(TBARS),color difference,sensory score and texture of chilled pork were tested every 3 day to evaluate the effect of SA-CH-CEO-Lip on the shelf life of meat.The results showed that on day 12,the p H value,TBC,and TVB-N of pork increased from 5.46,3.26 lg CFU/g,and 7.77 mg/100 g on day 0 to5.91,5.11 lg CFU/g,and 14.95 mg/100 g,respectively,without exceeding the minimum limits of 6.7,6 lg CFU/g,and 15 mg/100 g,respectively.TBARS and weight loss rate increased from 0.02 mg/kg and 3.17% to 0.49 mg/kg and 7.25%,respectively,and showed good color.Compared with the blank group,SA-CH-CEO-Lip could extend the shelf life of chilled pork for at least 12 days and better maintain the texture characteristics of pork. |
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