Esther Wanjohi, Elizabeth Tomasino, and James Osborne*
*Oregon State University, 3051 SW Campus Way, Corvallis, OR, 97331 
(james.osborne@oregonstate.edu)

Pediococci have been isolated from wines worldwide, but their specific effect on wine quality is not well described. Due to warmer growing seasons leading to higher-pH grapes and winemakers looking to reduce sulfur dioxide (SO2) use, the risk of Pediococci growth in wines is increasing. Therefore, this project aimed to characterize the sensory impact of Pediococcus on wine and investigated the effect of wine lees and nutrient additions on biogenic amine (BA) production. Nineteen Pediococcus isolates from Oregon, Washington, and California wines were inoculated into sterile filtered Pinot noir and growth was observed for 56 days, followed by the addition of SO2 and bottling. Differences in growth were observed, with many isolates maintaining a population similar to the initial inoculation rate (105 CFU/mL), while others declined in viability before recovering to higher populations. Experienced wine tasters using a modified napping method and ultra-flash profiling assessed the wines. No strong groupings of treatments based on aroma were observed, but there were two distinct groupings based on mouthfeel. One grouping was described as “Light,” “Thin,” and “Sharp,” while the other group was described as “Sticky,” “Medium,” and “Sharp.” These descriptors will be used to define additional chemical analysis. To explore factors affecting BA production by Pediococcus, different nutrient additions were made to Chardonnay juice prior to fermentation. The three nutrient addition treatments were control, high DAP, and high organic N. After completion of alcoholic fermentation, wines were cold-settled prior to racking (no-lees) or no racking (lees) treatments. Dimethyl-dicarbonate was added to kill background microorganisms and after 48 hrs, two BA-producing Pediococcus strains were inoculated into the wines. Growth was monitored for 60 days, after which samples were collected for analysis. BA will be assessed by liquid chromatography-mass spectrometry to determine the effect of nutrients and lees aging on BA production by Pediococcus.

Funding Support: This works was funded by the Northwest Center for Small Fruits Research (59-2072-1-008)