Effect of carrot residue on the desiccation and disinfectant resistances of food related pathogens adhered to a stainless steel surfaces

• Salmonella Typhimurium (ST) was dried with 50% (w/w) aqueous solutions of seven vegetables.
• The solutions of carrot and green bell pepper clearly protected ST from the desiccation.
• The carrot solution also tended to protect the dried Staphylococcus aureus (SA) cells.
• Adhered ST and SA were protected from some disinfectants by the carrot solution.
• These indicate that a small amount of carrot residues promotes cross contamination.

To clarify the effects of vegetable residues on the resistances of food-related pathogens to drying and disinfectants, Salmonella Thyphimurium was dried with 50% w/w aqueous solutions of seven vegetables and cell survival was assessed. Bacterial suspensions in distilled water or aqueous solutions (0.1 ml of 8 log CFU/ml) were placed on 50 mmφ stainless dishes and dried at room temperature for 120 min. In the absence of aqueous solution, cell numbers decreased from 6.9 to 3.6 log CFU/dish. The solutions of carrot (CR) and green bell pepper (GB) clearly protected the cells. CR and GB also tended to protect the dried Staphylococcus aureus cells. The adhered and dried pathogens with CR were treated with 0.1 ml of 0.01% w/v hypochlorous acid (HC), 70% v/v ethanol (ET), 0.2% w/v alkyldiaminoethylglycine hydrochloride (AH) or 0.2% w/v benzalkonium chloride (BC) for 10 min. Adhered S. Typhimurium cells were protected from HC and ET treatments by the carrot solution. S. aureus was protected from HC, ET, and AH. BC showed clear disinfectant activity under all conditions. These results suggest that trace amounts of carrot sediment protect the bacteria on surfaces from the desiccation and disinfectant treatments, and might also contribute to cross contamination.