The ability to produce 4-ethylphenol from the substrate p-coumaric acid in synthetic media was evaluated for several yeast species associated with wine production. Molar conversion rates as high as 90% were found by only Dekkera bruxellensis, D. anomala and by some unidentified strains isolated from wine-related environments. Other unidentified strains produced traces of 4-ethylphenol. All unidentified strains showed the same cultural characteristics as D. bruxellensis when grown on DBDM (Dekkera/Brettanomyces differential medium) agar. The determination of long-chain fatty acid compositions and the utilization of peptide nucleic acid (PNA) probes specific for D. bruxellensis showed that the unidentified strains did not belong to this species. Further identification, by restriction pattern generated from PCR-amplification of the 5.8S rRNA gene and the two internal transcribed spacers (ITS), assigned the unidentified strains to Candida cantarelli, C. wickerhamii, Debaryomyces hansenii, Kluyveromyces lactis and Pichia guilliermondii. However, only some strains of P. guilliermondii were capable of converting p-coumaric acid into 4-ethylphenol with efficiencies close to those observed in D. bruxellensis and D. anomala. r

In a survey of the microbial quality of raw materials used in fruit juice processing, yeast counts in fruit concentrates and pulps were found to range from 51to 2?9610 3 cfu g 71. Ascomycetous yeasts were represented by 76% of the isolates while 24% were basidiomycetes.The identi¢cation of strains isolated by the simpli¢ed identi¢cation system (SIM) revealed19 yeast species representing12 genera.The most frequently isolated yeasts belonged to the genera Saccharomyces, Pichia, Cryptococcus, Kluyveromyces and Candida. Fatty acid yeast composition allowed the separation of contaminating yeasts into one of three major groups. Group I included yeasts without linoleic (C 18:2) and linolenic (C 18:3) fatty acids such as Saccharomyces cerevisiae. Group II comprised yeasts without C 18:3 fatty acid like Zygosaccharomyces rouxii and Torulaspora delbrueckii, and group III included yeasts with C 18:2 and C 18:3 acids that belong, among others, to one of the following yeast genera: Pichia, Candida, Kluyveromyces or Cryptococcus. Species-speci¢c PCR primers were used for the rapid detection and identi¢cation of the most dangerous species a¡ecting fruit concentrate stability. The simpli¢ed protocol used consisted of PCR-ampli¢cation of conserved tracts in the ITS region of the rDNA unit, thus enabling the detection of potentially dangerous £ora such as Zygosaccharomyces species andT. delbrueckii in contaminated fruit concentrates. Results from PCR-typing were in full agreement with the fatty acid compositions of these species. The grouping of contaminant yeasts into three main groups showed that fatty acid composition may be used to di¡erentiate yeasts according to their technological signi¢cance.Yeasts isolated in this work as being most dangerous to product stability belong to either group II (Z. rouxii and T. delbrueckii) or group I (Saccharomyces spp.). Group III was comprised of several species regarded as indicators of de¢ciencies in 'good manufacturing practices'. Thus, each of the groups delineated may be considered to be a zymological indicator of technological signi¢cance. The conjugation of fatty acid pro¢les with PCR-typing methods may be used as a rapid detection system for contaminant yeasts. The fatty acid pro¢les provide a preliminary identi¢cation of yeasts potentially dangerous to product stability present