Potential of yeast isolated from apple juice to adhere to stainless steel surfaces in the apple juice processing industry

The aim of this study was to assess the potential of four yeast strains to initiate a biofilm on stainless steel. The yeasts were isolated from apple juice and were identified as Kluyveromyces marxianus, Candida krusei, Zygosaccharomyces sp. and Rhodotorula rubra. The physiochemical properties of cell surface were determined under different conditions. The adhesion capacity of the yeast strains to stainless steel was assayed in presence of apple juice. Cell surfaces were always negatively charged except for Zygosaccharomyces sp., whose isoelectric point was around 3.0. Neither electrophoretic mobility nor flocculation coefficient correlated with the capacity of attachment to stainless steel. The hydrophobicity expressed by the yeast surfaces at pH 3.0, correlated positively with the rate of adhesion (number of cells/min) of each strain. These results indicated that cell surface hydrophobicity governs the initial attachment of the studied contaminant yeast strains to stainless steel surfaces common to the apple juice processing plant.