Susceptibility of food-related yeasts to disinfectants in suspension and in artificial biofilm

Good production hygiene is a single most important factor in preventing microbial deterioration of food. Contaminated raw materials, processing equipment and packaging effectively transmit harmful yeasts to food. Yeasts can proliferate on process surfaces in biofilms, which protect cells from cleaning and disinfectants and serve as contamination sources. At present, information about the effectiveness of various cleaning and disinfecting agents against food-spoilage yeasts is sporadic and restricted to few species and sanitising agents. We evaluated the susceptibility of an extensive panel of food-related yeasts to common and novel sanitising agents using yeast suspensions and biofilms. Suspended cells were generally more susceptible to disinfectants than cells in biofilm. Only the alcohol-based disinfectant was also effective against biofilm cells. The tenside or peracetic based disinfectants or the chlorine-containing disinfectant or foam cleaner were not effective against yeasts in biofilm. The adhesive Candida intermedia, C. parapsilosis and Rhodotorula mucilaginosa strains showed resistance to these disinfectants even in suspension.