Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Controlling spoilage yeasts in food and beverages

Controlling spoilage yeasts in foods and beverages is being investigated. A collection of spoilage yeasts, isolated mostly from wines, olives, sugar syrups and yellow sauces, is being put together in order to obtain reference strains for the application of rapid techniques for typing and identification and also for tests on growth under a range of conditions. A particular strain of Zygosaccharomyces bailli (ISA 1307) was very resistant to sorbic acid and was used for a number of studies together with Saccharomyces cerevisiae. For example, the former grew at acetic acid levels up to 3.5% and the latter up to 1% at pH 4. The presence of acetic or benzoic acids decreased the temperature range at which these microorganisms grow indicating that viability at high or low temperatures is strongly influenced by the presence of preservatives. Z. bailli has an optimum temperature for growth of 32 C and has an associative temperature profile, i.e. death and growth co-exist in the temperature range 33-39 C. The presence of ethanol, acetic acid or sorbic acid cause a shift of the lethal temperature to lower values. However, this effect was less pronounced in Z. bailli than in S. cerevisiae. Both strains also have the ability to extrude benzoic acid during growth in the presence of almost any weak acid; the physiological relevance of this phenomenon is being investigated. Resistant strains of Z. bailli and Pichia membranaefaciens can grow in sorbic acid concentrations of 650 parts per million (ppm) and the former can also grow on 70% glucose.

Reported by

Instituto Superior de Agronomia
1399 Lisbon
Portugal
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