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Please use this identifier to cite or link to this item: http://hdl.handle.net/10400.5/491

Title: Zymological indicators: a new concept applied to the detection of potential spoilage yeast species associated with fruit pulps and concentrates
Authors: Malfeito-Ferreira, Manuel
Loureiro, Virgilio
Sancho, T.
Gimenez-Jurado, G.
Keywords: zymological indicators
fruit pulp
fruit concentrate
yeast
Issue Date: 2000
Publisher: Academic Press
Citation: "Food Microbiology". ISSN 0740-0020. 18 (2000) 000-000
Abstract: 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 from51to 2?96103 cfu g71. Ascomycetous yeasts were representedby 76%of the isolateswhile 24%were basidiomycetes.The identi¢cation of strains isolated by the simpli¢ed identi¢cation system(SIM) revealed19 yeast species representing12 genera.Themost frequently isolated yeasts belonged to the genera Saccharomyces, Pichia, Cryptococcus, Kluyvero- myces and Candida. Fatty acid yeast composition allowed the separation of contaminating yeasts into one of threemajor 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 Zygosaccharo- myces rouxii and Torulaspora delbrueckii, and group III included yeasts with C18:2 and C18:3 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 ofpotentially 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 threemain groups showed that fatty acid compositionmay be used to di¡erentiate yeasts according to their technological signi¢cance.Yeasts isolated in thiswork 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 within 48 h. of isolation. Whereas the PCR-typing method is mainly used to confirm isolate identity, when required, after the initial diagnosis has been performed, over a period of 4 h.
Description: DOI:10.1006/fmic.2000.0360; available online at http://www.idealibrary.com
URI: http://hdl.handle.net/10400.5/491
ISSN: 0740-0020
Appears in Collections:DBEB - Artigos de Revistas

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