Evaluación de la calidad microbiológica de tapones de corcho para vinos elaborados en Catalunya

Abstract

The need to establish suitable methods that allow for quality control in alimentary products, or for items that are to be in close contact with food and drink products is of primary importance, and determines the approach adopted by this discussion. For this reason, the general purpose of this study is to evaluate the factors that affect the microbiological quality of natural cork bottle stoppers for sparkling and still wines produced in wine-making factories within Catalonia.<br/><br/>The method of reference taken by this work is the "Norma Catalana Nº 0.20/95", which establishes the methodology for the microbiological analysis of cork bottle stoppers for wines. The assessment of this regulation was undertaken by using control cork stoppers experimentally inoculated with fungal conidia, yeast and bacteria of known concentration. Subsequently, different washing solutions were tested, along with various types of and timings for mechanical shaking, different culturing media as well as incubation times and temperatures. <br/><br/>The results obtained indicate that physiological or Ringer _ solution can be used as washing solution; stoppers should be washed for 30 minutes at 150 or 200 rpm, filters should be sown in agar soya tryptone (TSA) at 37ºC+ 2ºC for 24 hours for the recuperation and recount of bacteria, and Sabouraud agar dextrose (SDA) at 28ºC + 2ºC for 48 hours for the recuperation and recount of filamentous fungi and yeast.<br/><br/>Additionally, the results obtained in applying this methodology were compared with the results obtained in applying the methodologies established by ISO regulation 10718:1993, the method of serialised decimal dilution and the Miliflex-100® System. It was observed that the invasive micro-organism growth upon application of ISO regulation 10718:1993 impedes their recount, that the method of serialised decimal dilution is appropriate for highly contaminated samples and that micro-organism recounts are similar when the Miliflex-100® System is applied.<br/><br/>The recount, isolating and identification was undertaken of organisms present in samples of cork bottle stoppers for wines appliying the methodology proposed in this study, establishing that the recount of UFC/stopper for bacteria in the samples analysed are within the limits of acceptability set out by the Norma Catalana Nº 0.20/95, but not to the acceptable limits for filamentous fungi and yeast. Furthermore, the type and species of isolated micro-organisms coincide with the microbiota previously described for this substrate.<br/><br/>The enzymatic and inhibitory activity of the isolated micro-organisms was determined, and it was observed that they all presented naphthol-A-S-BI-phosphohydrolase activity. Micro-organisms presenting greatest enzymatic activity are: Alternaria alternata, Aspergillus niger and Monilia sitophila. Micro-organisms presenting greatest inhibitory activity against filamentous fungi, yeast and bacteria studied are: Penicillium citrinum and Trichoderma viride.<br/><br/>Finally, the production was studied of micotoxins developed and accumulated by the samples' isolated filamentous fungi. Tests undertaken show that A. alternata produces altertoxine I, altenuene, alternariol and alternariol monomethylic ether; P. citrinum produces citrinine and Fusarium moniliforme produces fumonisine B1.

Date of Award	4 Apr 2001
Original language	Spanish
Supervisor	Maria Dels Angels Calvo Torras (Director) & Isabel Esteve Martínez (Director)