Cross-contamination Of Aeromonas Spp. Between Different Food Contacts In The Kitchen

Cross-contamination of Aeromonas spp.from chilled pork to Brassica chinensis under various food-handling scenarios was studied in this thesis by mimicking the food preparation process of consumer in the kitchen.The analogue simulation of cross-contamination showed that contaminated B.chinensis suggested some potential risks for consumers.Then,recovery ratios of Aeromonas spp.using swabbing method from cutting boards and knives were examined.Mathematical models describing survival of Aeromonas spp.on cutting boards and knives as a function of time were also proposed.Meanwhile,in term of cutting boards as the cross-contamination approach,combining survival model and further study were conducted to investigate the influence of the survival of Aeromonas spp.on the cross-contamination level.Results indicated that models without survival models would overestimate the risk associated to cross-contamination.In addition,cross-contamination of Aeromonas spp.among different mediums was quantified based on matrix method,which means the change in the number of Aeromonas spp.on both donor surface and recipient surface could be calculated simultaneously.Above study could provide theoretical references for complete establishment of Aeromonas spp.risk assessment.The detailed contents and conclusions conclusions of this dissertation were as follows:Firstly,this part was designed to quantify the cross-contamination of Aeromonas spp.from chilled pork to B.chinensis through cutting boards,knives and hands in the kitchen.Transferring experiments were performed to mimic the food preparation process of consumer under laboratory conditions.The pork sample was inoculated with Aeromonas spp.before splitting in order to determine the transfer rate of Aeromonas spp.from chilled pork to cutting boards,knives and hands,respectively;Meanwhile,transfer rates from cutting boards,knives and hands to B.chinensis under various food-handling scenarios were also determined.Transfer rates were logarithmic transformed to fit distributions and following scenario 1 i.e.after cutting pork,cutting boards,knives and hands were also used for cutting B.chinensis without any cleaning was taken for example to simulate cross-contamination.Results showed that each trial of transfer rates varied over experiments significantly(P<0.05),and transfer rates with logarithmic transformation proved to be fit for approximate normal distribution.The analogue simulation of cross-contamination showed that cross-contamination of foodborne pathogens from raw meats to ready-to-eat foods suggested some potential risks for consumers.Secondly,the recovery ratios of Aeromonas spp.using swabbing method from cutting boards and knives were examined.Then,the survival of Aeromonas spp.on clean and contaminated cutting boards,stainless steel knives surfaces was studied.Based on the survival data and recovery ratios of Aeromonas spp.,expected numbers of Aeromonas spp.on cutting boards and knives were calculated.Mathematical models describing survival of Aeromonas spp.as a function of time were also proposed.Meanwhile,in term of cutting boards as the cross contamination approach,combining survival model and further study were conducted to investigate the influence of the survival of Aeromonas spp.on the cross contamination level.Results indicated that the best fitting of recovery ratios of Aeromonas spp.from cutting boards and knives obtained by @Risk software were Normal(0.66,0.15)and Normal(0.72,0.18),respectively.And Aeromonas spp.proved to survive longer on the contaminated cutting boards and knives than on the clean ones.Survival data for Aeromonas spp.could be well described by linear model(R2>0.88),and models without survival models included would overestimate the risk associated to bacterial transfer.Thirdly,the transfer approach and transfer probability of Aeromonas spp.under various food-handling scenarios were centralized in a two-dimensional data table by applying matrix method,which aimed at quantifying cross-contamination of Aeromonas spp.among different food-contact surfaces.Results showed that the number of Aeromonas spp.on donor and recipient surface could be calculated simultaneously,for instance,the average value of Aeromonas spp.in chilled pork before and after cross-contamination were 3.02 lg CFU/g,1.82 lg CFU/g,respectively.Results also confirmed that proper conducts after splitting pork including cleaning contaminated boards,knives,hands or just changing them into clean ones before splitting B.chinensis could reduce cross-contamination level effectively.The study of microbial cross-contamination could be helpful for setting good hygienic practice guidelines for consumers and could provide a theoretical basis for assessing the potential hazard of cross-contamination.