2013 Annual Report
1a.Objectives (from AD-416):
1. Isolate and identify Pediococcus spp. from Oregon wines.
2. Determine the impact of Pediococcus spp. from Oregon and Washington wines on wine quality.
3. Evaluate the effect of sulfur dioxide on pediococci.
1b.Approach (from AD-416):
Wines will be produced from both Syrah and Pinot noir grapes and inoculated with pediococci previously isolated from wines. Bacterial growth, changes in chemical composition (volatile acidity, diacetyl, etc.), and the synthesis of biogenic amines will be determined using already established methods. Wines will be further analyzed by sensory evaluation using a trained panel.
This research was conducted in support of NP 305 objective 1 "Determine nutrient requirements to enhance product quality in woody perennial crops such as grapevine and rhododendron" of the parent project. Pediococcus have been isolated from wines worldwide and are generally regarded as being wine spoilage organisms. However, little is known concerning the occurrence of these organisms in Washington and Oregon state wines or their impact, if any, on quality. To determine this Pediococcus (P. parvulus (7), P. damnosus (1), and P. inopinatus (1)) were isolated from Oregon and Washington state wines. These isolates were inoculated into a Pinot noir wine that had been produced at the OSU research winery (sterile filtered, pH 3.75, no SO2 addition, and no malolactic fermentation). After significant growth of the pediococci isolates had occurred samples were analyzed for a number of spoilage products including biogenic amines. Growth of the pediococci isolates in Pinot noir wine resulted in a number of chemical and sensory changes occurring compared to the control. Very low concentrations of biogenic amines were measured in the wines with only wine inoculated with P. inopinatus OW-8 containing greater than 5 mg/L. D-lactic acid production varied between isolates with OW-7 producing the highest concentration (264 mg/L). Diacetyl content of the wines also varied greatly. Some wines contained very low levels of diacetyl (< 0.5 mg/L) while others contained very high concentrations (> 15 mg/L) that were well above sensory threshold. Color and polymeric pigment content of the wines also varied with wine inoculated with OW-7 containing 30% less polymeric pigment than the control. This may have been related to acetaldehyde concentration as a number of Pediococcus isolates, including OW-7, reduced the acetaldehyde content of the wine. Sensory analysis by a trained panel revealed differences in the aroma and mouthfeel of the wines compared to each other and to the control. In particular, growth of some isolates produced wines with higher intensities of butter, plastic, and vegetal aromas while other also had lower perceived astringency. The ability of Pediococcus to produce volatile phenols was also assessed. In media all isolates degraded p-coumaric acid to 4-vinyl phenol but not to 4-ethl phenol. However, the conversion of p- coumaric to 4-vinyl phenol resulted in accelerated production of 4-ethy phenol by B. bruxellensis in a model system. The SO2 tolerance of the pediococci isolates was determined in a model system. Tolerance to SO2 varied between isolates with some growing well at levels of 0.4 mg/L molecular SO2.