| A survey of aerobic bacteria, Escherichia coli, filamentous fungi and yeast on fresh strawberry was conducted in Hangzhou. In this study, tap water, sodium hypochlorite, lactic acid, malic acid, citric acid, sodium chlorite and acidified sodium chlorite were used to wash the strawberries to remove the microbes and the best antibacterial method was determined. Then the best antimicrobial cleaning method was applied to strawberry samples antibacterial cleaning and compared microorganisms including aerobic bacteria, Escherichia coli, filamentous fungi and yeast before and after washing. Quantitative risk assessment of Salmonella on strawberry was carried out. By combining Salmonella initial contamination data, strawberry consumption data, dose-response model and predictive model of retail to home, home storage, household cleaning, the risk of six consuming strawberry behaviors was conducted. The main contents and results of this study are summarized as follows:1. A total of50strawberry samples were collected from supermarkets, fruit shops and traditional market in Hangzhou to investigate the contamination level of aerobic bacteria, Escherichia coli, filamentous fungi and yeast. The detection methods were referred to the national standards GB/T4789.2-2010aerobic bacteria, GB/T47893-2010Escherichia coli, GB/T4789.15-2010molds and yeasts. The results showed that the concentration of aerobic bacteria, Escherichia coli, filamentous fungi and yeast on fresh strawberries were within102～105CFU/g,0～10MPN/g,102～103CFU/g, are103～104CFU/g. There is a potential health risk in the contaminated strawberries.2. In this study, strawberries were washed by tap water,0.02%sodium hypochlorite,2.0%lactic acid,2.0%malic acid,2.0%citric acid,0.1%sodium chlorite and0.1%acidified sodium chlorite (pH2.3) for2and10min, respectively. The results indicated that the best antimicrobial method was washing with0.1%acidified sodium chlorite for2min, followed by washing with2.0%lactic acid for10min.3. The solution of0.1%acidified sodium chlorite was applied to wash strawberries and inactivation effects of aerobic bacteria, Escherichia coli, filamentous fungi and yeast were compared. The results showed that there was a significant microbial reduction of aerobic bacteria (p<0.05), Escherichia coli (p<0.0001) and filamentous fungi (p<0.05), the average value of yeast of washed strawberry is1/20of yeast of unwashed strawberry.4. The sterile strawberries were inoculated with Salmonella with an initial contamination level of104log CFU/g-105log CFU/g and then storage at4℃. The bacterial level was record every8h. The results showed that Salmonella on strawberry was in reducing trend and the linear model could be used to fit the bacterial reduction. The regression coefficient R2=0.99. Model fitting accuracy factor (Bf) and accuracy factor(Af) were0.97and1.09, respectively, which indicated it would be a good behavior of the predictive model.5. The sterile strawberries were inoculated with Salmonella with an initial contamination level of102log CFU/g～103log CFU/g and then storage at22℃. The bacterial level was record every8h. The results showed that Salmonella on strawberry was in growth trend and the linear model could be used to fit the bacterial reduction. The regression coefficient R2=0.99. Model fitting accuracy factor (Bf) and accuracy factor (Af) were0.91and1.1, respectively, which indicated it would be a good behavior of the predictive model.6. The sterile strawberry was inoculated with Salmonella with an initial contamination level of104log CFU/g～105log CFU/g and washed40s.80s.120s.160s.200s.240s by47℃.50℃.53℃tap water, respectively. The results showed that Salmonella on strawberry was in reducing trend and fitted into a Weibull equation, The regression coefficient R2=0.99.Model fitting accuracy factor (Bf), accuracy factor (Af) were1.03and1.14,respectively. The effect of model fitting is good.7. The risk of six consuming behaviors which contain unwashed and room temperature storage behavior、unwashed and4℃temperature storage behavior、tap water washing and normal temperature storage behavior、tap water washing and4℃temperature storage behavior、warm water washing behavior and normal temperature storage and warm water and4℃temperature storage behavior was8.15×10-4、4.53×10-6、2.08×10-3、8.34×10-6、2.74×10-4、4.9.14×10-7,respectively.8. Assuming probability of six consuming behaviors being same and comparing the risk of six consuming behaviors. As the baseline model, the risk of unwashed and room temperature storage behavior is set to1. Compared with other five consuming behaviors, the average risk of unwashed and4℃temperature storage behavior, tap water washing and normal temperature storage behavior, tap water washing and4℃temperature storage behavior, warm water washing and normal temperature storage behavior, warm water and4℃temperature storage behavior was42.1%,15.8%,25.3%,3.87%,6.51%average risk of baseline model, respectively. |
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