Study On Biological Hazards Of Food By Biofilm

Biofilm formation of foodborne pathogenic bacteria on stainless steel surface and their sensitivity to disinfectants were studied, which could be used in cleaning and sterilizing equipments during food processing.After Measuring the growth curves of foodborne pathogenic bacteria biofilms by establishing their biofilms modeling on stainless steel surface and the growth curves of foodborne pathogenic bacteria, then analysised the biofilm formation of foodborne pathogenic bacteria biofilms on stainless steel surface. The samples were then detected by scanning electron microscopy (SEM), the optical density of bacterial biofilm was determined by using computer image analysis system. The viable counts of bacteria in biofilm were detected by the method of plating of swabbing. The minimal eradication concentration (MEC) of disinfectants for biofilm and suspensions was determined by test tube dilution method.The foodborne pathogenic bacteria biofilms on stainless steel surface were obtained after incubation in trypease soy broth (TSB) for 7 d with a cell density of 106 cfu/cm2. The SEM graphs showed that bacteria of Salmonella sp. (AS 1.1552) were bacillus and Staphylococcus aureus (AS 1.89) were coccus, which surrounded by accidented material and the bacteria were connected each other by slimes to form biofilm.The factors about concentration of available chlorine, concentration of TSB culture medium and contact time of disinfectant could influence the germicidal efficacy. The results showed that disinfectants (soclium hypochlorite and chlorine dioxide) containing available chlorine 50~100 mg/l with more 20 min contact time killed 100% of suspensions with a cell density of 106 cfu/ml and disinfectants containing available chlorine 100-150 mg/1 with more 20 min contact time killed 100% of biofilm with a cell density of 106 cfu/cm2 in 0% (w/v) TSB culture medium. Disinfectants containing available chlorine 150 mg/1 with 30 min contact time killed 100% of suspensions with a cell density of 10 cfu/ml and disinfectants containing available chlorine 400mg/l with 30 min contact time killed 100% of biofilm with a cell density of 106 cfu/cm2 in 3.0% (w/v) TSB culture medium. Chlorine dioxide was better than sodium hypochlorite in germicidal efficacy.