Abstract:
Factors affecting attactment and biofilm formation of Pseudomonas fluorescens TISTR 358 on food contact surface made of stainless steel grade 304/2B were studied, namely initial load of bacterial contamination in the medium, temperature and type of contaminated medium. The studies were done by following the attachment and biofilm formation on the stainless steel coupons for 48 hours under three different treatments: (i) initial inoculums in the medium (8 log and 3 log CFU/mL), (ii) incubation temperature (15, 20 and 30 °C), (iii) type of medium (0.85% NaCl, TSB, soiling agent (beef meat 5% w/v)). It was found that at 0 minute (immediately contact) bacterial cell in the contaminated medium can attach and grow on coupons. The influence of incubation temperature and initial cells of inoculums were studied together. The results showed that at initial contamination load of 3 log CFU/mL, no cell can be detected up to 9 hours but at 24 and 48 hours the number of the bacterial cells were 3.72 ± 0.34 and 5.05 ± 0.18 log CFU/cm2, respectively. The experiment using 8 log CFU/mL gave similar results. The number of the bacterial cells on coupons at 28 °C was higher than at 20 and 15 °C, respectively. Whereas, cells could attach and form biofilm nearly the same in different medium (0.85% NaCl, TSB, soiling agent) at 24 hour. The transfer of P. fluorescens cells and P. fluorescens Biofilm from a contaminated domestic slicing machine to a cooked meat product during slicing were studied. The results showed that the number of cells transferred per slice during slicing by blade contaminated with P. fluorescens Biofilm was higher than blade contaminated with P. fluorescens cells. For the high contaminated medium of 8 log CFU/mL, the number of cells in the last slice (20 slices) of meat in the case of blade contaminated with P. fluorescens Biofilm and contaminated with P. fluorescens cells were 4.15 ± 0.08 and 2.39 ± 0.17 log CFU/g, respectively. While for the low contaminated medium of 3 log CFU/mL, the number of cells in the last slice (20 and 11 slices in contaminated with P. fluorescens Biofilm and with P. fluorescens cells, respectively.) of meat in the case of blade contaminated with P. fluorescens Biofilm and with P. fluorescens cells were 1.83 ± 0.12 log CFU/g and 1.09 ± 0.04 log CFU/g, respectively.The efficacy of sodium hypochlorite (NaOCl) and peroxyacetic acid (POA) were investigated. In planktonic cells, the results showed that NaOCl and POA 100 ppm completely eliminated cells within 1 minute in high contaminated (8 log CFU/mL)0.85% NaCl. However, the same concentration of NaOCl showed less effective in eliminating cells when tested in both TSB or soiling agent. The efficacies of both sanitizers on Pseudomonas biofilm were test at 30 minutes. The results showed that at NaOCl 400 ppm couldnt completely eliminate cells in biofilm but POA 50 ppm could completely eliminate cells in biofilm.