RESUMO
Some yeast strains belonging to the species Zygosaccharomyces rouxii and Debaryomyces hansenii are capable of spoiling sorbate containing high-sugar foods by producing pentadiene, a volatile compound reported to have 'petroleum-like' odour. Quantification of the diminution of sorbate and the subsequent increase of pentadiene was performed by growing the yeasts in experimental media containing 600 g/l sucrose and different sorbate concentrations. Final sorbate concentrations were notably lower than their corresponding initial ones, and it was found that the higher the initial concentration of sorbate in the media, the higher the amount of pentadiene produced. In all cases, Z. rouxii was able to produce more pentadiene than D. hansenii when expressing pentadiene concentration as a function of cell biomass. These results suggest that pentadiene is a metabolite of sorbate.
Assuntos
Alcadienos/metabolismo , Conservantes de Alimentos/farmacologia , Saccharomycetales/metabolismo , Ácido Sórbico/farmacologia , Zygosaccharomyces/metabolismo , Relação Dose-Resposta a Droga , Conservação de Alimentos/métodos , Conservantes de Alimentos/metabolismo , Concentração Osmolar , Saccharomycetales/efeitos dos fármacos , Ácido Sórbico/metabolismo , Zygosaccharomyces/efeitos dos fármacosRESUMO
A selective and differential solid medium for the specific detection of some common yeasts frequently causing spoilage in intermediate moisture foods is described. The principle of the method is based on the detection of two enzymes, beta-glucosidase and beta-galactosidase, using the chromogenic substrates salmon-Gluc and X-Gal. Over 140 yeasts and bacteria were tested, and Debaryomyces hansenii and Kluyveromyces marxianus strains produced salmon and dark blue colonies, respectively, thus permitting their clear discrimination from other yeasts common in intermediate moisture foods. The medium was very satisfactory when intermediate moisture foods were tested.