Fungi associated with orange juice production and assessment of adhesion ability and resistance to sanitizers

Abstract

Orange juice is widely consumed worldwide due to its sensory and nutritional characteristics. This beverage is susceptible to contamination by acidic-tolerant microorganisms due to its low pH, especially filamentous fungi and yeasts. To minimize fungal spoilage, companies usually submit juice to thermal treatments; sanitizers are also applied on surfaces to maintain the microbiological quality. This study aimed to identify potential contamination sources in a juice processing line and to verify the susceptibility of isolated yeasts and filamentous fungi to food-grade sanitizers. Also, their ability to form single and binary adherent cells was assessed. The results revealed the presence of fungi in all samplings performed, with the most prominent microorganisms identified as Paecilomyces variotii, P. paravariotii, Pichia kudriavzevii and Wickerhamomyces anomalus. After obtaining results for sanitizer resistance and adhesion ability of the isolates, these were submitted to multivariate analysis using hierarchical cluster analysis (HCA), and two groups were found: one composed mostly of filamentous fungi (16/18) with low adhesion potential and one group formed by yeasts with high adhesion ability and resistance to sanitizers. Microscopy images corroborate those data, demonstrating the importance of yeast cell agglomerates along germinated spores of filamentous fungi and the importance of adhered biomass to protect cells against the sanitizers tested. This study is the first to combine fungi isolated from a beverage processing line and aims to contribute to the current knowledge of fungal adhesion and sanitizer resistance.

Keywords: Adhesion to surfaces; Orange juice; Processing line; Sanitizers; Spoilage; fungi.