Study On Preservation Of Fresh-cut Apples By The Extraction Of Cinnamon And Establishment Of The Growth Model Of Listeria Monocytogenes

Fresh-cut fruits and vegetables become more popular because of convenience.Compare to the normal fruits and vegetables,the fresh-cut fiuits and vegetables are prone to the problems such as nutrient losses,tissue damage,microbial infection and other issues.In addition,Listeria monocytes is one of the pathogens which can grow at low temperature.The preservative effect and antibacterial properties of cinnamon extract on fresh-cut apples were determined.The antibiotic ability of extract using different extraction methods(ethanol extraction,ethanol reflux and ultrasonic)were discussed.And the results showed that ultrasonic extraction showed the strongest antimicrobial effect against Listeria.Combining the method of ethanol reflux and ultrasound,it indicated that the extract of cinnamon refined by 95%ethanol 45 min for 2 h after ultrasonic process had the best inhibitory effect on Listeria.At the same time,the extract had the minimum inhibitory concentration(MIC)of 7.81 mg/mL on Listeria.The fresh-cut apple was treated with different concentrations of cinnamon extract.The results indicated that the extract at concentration of 10%was demonstrated the best antibacterial activity,Water loss rate,content of vitamin C,organic content,respiration,relative conductivity,hardness,enzyme content and soluble solids of fresh-cut apples were measured regularly.The fresh-cut apples treated with the extract showed a lower level of loss rate,respiration rate,relative conductivity,activity of polyphenol oxidase(PPO)and the color changes,but higher level of content of organic acid,soluble solids,hardness,and activity of peroxidase(POD)and.The results showed that the extract had the better effect on the preservation of fresh-cut apples.The vivo growth curve of Listeria in fresh-cut apples was described by the method of predictive microbiology.The result indicated that the growth curve of Listeria at different temperatures,cinnamon extractions and pH matched the Gompertz model.The parameters of Listeria were calculated at different experimental conditions by using the Gompertz growth model.According to the growth parameters of Listeria from the Gompertz model,the square root equation was established.It can fit the lag time(Lag)and the maximum growth rate(?max)of Listeria at the range of temperature from 4? to 20?,cinnamon extraction concentration from 0 to 10%and pH from 3 to pH 6.Results indicated that the effect of temperature and combined extract concentration had significant effect on the growth of Listeria.Compared with the relative error of the predicted value and the actual value of the quadratic polynomial regression,the growth model of Listeria in fresh-cut apples was obtained.