Historically, winemakers have viewed Brettanomyces sp. as producing spoilage in wines. Despite traditionally negative connotations surrounding the yeast, some are now questioning whether or not subtle “Brett” character, in some cases, may play a positive role in flavor and bouquet development. In addition to potentially contributing to complexity, limited Brettanomyces activity may play a role in accelerated aging in young red wines. Of the nine species of Brettanomyces isolated from wine and juice, B. intermedius is the most frequently identified. This suggests the existence of several, to many, strains that may be involved in the winemaking process. Prior to this study, a comprehensive evaluation of inter- and intrastrain variability has not been undertaken. The objective of this two-year project is to study inter- and intrastrain differences between ten genetically characterized strains of the single species, Brettanomyces intermedius, in aging red wine (Pinot Noir). The project includes comparison of population dynamics as well as chemical and sensorial changes brought about during the growth phase of the respective strains. The goals of the first year were to characterize population changes often strains of B. intermedius in Pinot Noir wine incubated at 20°C and begin GC/MS identification and quantification of primary metabolites. Presently, we are in week 45 of the growth studies inoculated at, <10 CFU/ml. We have observed that three of the ten strains reached maximum cell density at 41 days post-inoculation. Five strains took 60 to 140 days to complete their growth cycle. Final population densities, in these cases, paralleled those of the early group. Two of the ten strains grow very slowly. At present (day 195), both are approaching stationary phase. Depending upon strain and replication, cell density ranges from 28,000 to 50,000 CFU/ml. CG/MS analysis of weekly samples is approximately 60%complete. In every case, 4-ethyl phenol was not detected until cell density reached relatively high numbers. These preliminary results appear to contradict the belief that 4-ethyl phenol can be used as a monitoring tool for population density estimates in the earliest stages of growth. Work also continues on monitoring ieto-glucosidase activity in inoculated wines. Initial results suggest potentially significant enzyme activity in model systems. Follow-up assays are currently being carried out in experimental lots. Upon completion of the growth cycles, each lot was cold-clarified, bottled and stored for upcoming sensory examination. Year two objectives: At four, and nine months post-bottling, each lot will be examined sensorially for differences. Initial sensory comparison of each lot will be carried out using Duo-Trio paired comparison tests. Where differences are noted, descriptive analysis will be performed using a twelve member trained panel.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF1997-10-18 14:58:462017-10-18 14:59:24Effects of Brettanomyces in Winemaking: Chemical, Microbiological and Sensoriale