Thermal I Activatio of the Wi E Spoilage Yeasts Dekkera/bretta Omyces

In studies employing tartrate buffer as the heating menstruum, measurable thermal inactivation began only at temperatures of 50oC. When heating was performed in wine, significant inactivation begins at 32.5oC. In the range of pH values tested (2.5 to 5.0), this factor showed no significant influence in the heat inactivation kinetics (Table 1). In the experiments done with different phenolic acids, all compounds caused a decrease in the D values, ferrulic acid having the strongest effect (Table 2). Results from experiments in buffer with added ethanol suggest that the greater heat sensitivity shown in wines can be largely attributed to ethanol (Table 3), although potentiation of this effect might be due to the phenolic content (Figure 1). Analysing the results obtained in wine (Table 4), there is a slight difference in the heat resistance of the three strains. Apparently, the strain isolated from wine is more resistant in wine than the collection ones. There is also a difference in heat resistance of the collection strains in wine A and B, which might be explained by the difference in ethanol concentration of the two wines. As an illustration 6D inactivation regimes are, in wine A and for Dekkera 093, 37.50oC for 4.80 min or 43.67oC for 0.63 min (Table 5). DISCUSSION