PCR-fingerprinting and RAPD approaches for tracing the source of yeast contamination in a carbonated orange juice production chain

Aims: To investigate the sort and the origin of the contamination of a packed fruit juice. Methods and Results: Fifty-eight yeast isolates were collected in a survey of two different visits to a carbonated orange juice factory. In each visit, samples were collected, six times, from seven points in the production chain. For each visit, no significant differences were observed among the yeast average values obtained in the control points considered. The random amplified polymorphic DNA (RAPD) with primer P24 and the PCR-fingerprinting with the microsatellites primers (GTG)(5) and (GAC)(5) were used, in order to discriminate the isolates, rendering 29 composite profiles; the most frequent one (24/58) was profile c, which included the yeast isolates from the final product and strains isolated before and after the pasteurization of the juice. These contaminant strains were identified as Pichia galeiformis by sequence analysis of D1/D2 26S rRNA gene. Conclusions: The results obtained point to an inefficient pasteurization of the juice related to the fouling of the heat-transfer surfaces of the plate-type exchanger. Significance and Impact of the study: The combination of PCR-fingerprinting and RAPD assays showed to be very useful in tracking the route of contamination in a carbonated juice production chain.