Effects of Combined Treatment of Sodium Hypochlorite/Ionizing Radiation and Addition of Vitamin B1 on Microbial Flora of Oyster and Short-Necked Clam

Inhibitory effect of ethanol and thiamine dilaurylsulfate against loosely, intermediately, and tightly attached mesophilic aerobic bacteria, coliforms, and Salmonella Typhimurium in chicken skin

The effects of 3 ethanol levels (30, 50, and 70%) with and without thiamine dilaurylsulfate (TDS; 1,000 ppm) were evaluated for the reduction of natural mesophilic aerobic bacteria (MAB), coliforms, and inoculated Salmonella Typhimurium (S. Typhimurium) in chicken skin. The chicken skin was inoculated with a 7 log cfu/mL suspension of S. Typhimurium. Loosely, intermediately, and tightly attached cells were recovered from chicken skin through shaking at 200 rpm for 5 min, stomaching for 1 min, and blending for 1 min, respectively. Increasing the ethanol concentration reduced the number of MAB, coliforms, and S. Typhimurium on the chicken skin, whereas TDS treatment without ethanol was not effective. Intermediately and tightly attached microorganisms (total MAB, coliforms, and S. Typhimurium) were more resistant to chemical disinfectants than loosely attached microorganisms. The combination of 70% ethanol with TDS was most effective than the combination of TDS with lower concentrations of ethanol in reducing populations of loosely, intermediately, and tightly attached MAB (by 1.88 log cfu/g, 1.21 log cfu/g, and 0.84 log cfu/g, respectively), coliforms (by 1.14 log cfu/g, 1.04 log cfu/g, and 0.67 log cfu/g, respectively), and S. Typhimurium (by 1.62 log cfu/g, 1.72 log cfu/g, and 1.27 log cfu/g, respectively). However, the chicken skin treated with higher concentrations of ethanol was tougher (P < 0.05) and more yellow and less red (P < 0.05) than that treated with lower concentrations of ethanol or with water (control). On the other hand, a combination of 30% ethanol and TDS yielded the best results, showing the reduction greater than 0.5 log cfu/g in S. Typhimurium, with no negative effect on chicken skin color or texture. Thus, a combination of 30% ethanol and TDS appears to be the optimal treatment for reducing microbial contamination of skin-on chicken products to enhance poultry safety without decreasing food quality, and this treatment could be applied in the poultry industry.

Synergistic Effects of Combined Chlorine and Vitamin B1 on the Reduction of Murine Norovirus-1 on the Oyster (Crassostrea gigas) Surface

This study investigated the synergistic effects of combined chlorine (200, 500, 700, and 1000 ppm) and vitamin B₁ (1000, 2000, and 3000 ppm) on the murine norovirus-1 (MNV-1), a human norovirus (NoV) surrogate, on oyster surface. Vitamin B₁ slightly reduced MNV-1 (0.04-0.3 log-reduction), whereas chlorine significantly reduced MNV-1 (0.4-1.0 log-reduction). The combined chlorine and vitamin B₁ resulted in a 0.52-1.97 log-reduction of MNV-1. The synergistic reduction in the MNV titer was not dependent on the concentrations of chlorine and vitamin B₁, and it ranged between 0.08 and 1.03 log₁₀ PFU/mL. The largest synergistic reduction observed was for the combined 700 ppm chlorine and 1000 ppm vitamin B₁. The pH and mechanical texture of the oysters were not significantly changed by the combined 0-1000 ppm chlorine and 3000 ppm vitamin B₁. The overall sensory acceptability were significantly (P < 0.05) reduced in oysters treated with 1000 ppm chlorine and 3000 ppm vitamin B₁ than in those treated with 0-700 ppm chlorine and 3000 ppm vitamin B₁. This study suggests that the combined 700 ppm chlorine and 3000 ppm vitamin B₁ could potentially be used to reduce NoV on oyster surface without causing concomitant changes in the mechanical texture, pH, or sensory qualities of the oysters.

Evaluation of the removal and destruction effect of a chlorine and thiamine dilaurylsulfate combined treatment on L. monocytogenes biofilm

The present study investigated the efficacy of single and combined treatment of both chlorine and thiamine dilaurylsulfate (TDS) on the reduction of Listeria monocytogenes biofilms in microtiter plate. The disinfectants used in this study were 50, 100, and 200 mg/L chlorine and 100, 500, and 1000 mg/L of TDS. Biofilm-forming index (BFI) and culturable cell count were used to evaluate the disinfectant assay. The highest BFI reduction was 0.80, achieved by the combination of 200 mg/L chlorine and 1000 mg/L TDS. In contrast, the highest culturable cell count reduction was 4.80 log colony-forming units/well by the combination of 200 mg/L chlorine and 100 mg/L TDS. The BFI was reduced in a concentration-dependent manner while culturable cell count was significantly reduced only when all chlorine concentration was combined with 100 mg/L TDS. However, when chlorine was combined with a higher concentration of TDS, the reduction decreased significantly. The result in this study showed that the combination of the 200 mg/L chlorine and 1000 mg/L TDS could be a practical application in removing L. monocytogenes biofilms from surfaces in food industry, and for the 200 mg/L chlorine and 100 mg/L, it can be used for killing the pathogen biofilms. However, more studies are still needed in order to show its efficacy on foods surfaces as well as to develop an even more effective treatment in both killing and removing biofilms.