Location: Horticultural Crops Production and Genetic Improvement Research Unit
Project Number: 2072-21000-057-027-G
Project Type: Grant
Start Date: Sep 1, 2021
End Date: Oct 31, 2025
Objective:
1. Isolate and identify Pediococcus spp. from Oregon and Washington state wines;
2. Screen Pediococcus isolates for sensory impact on standard wine;
3. Characterize the sensory impact of select Pediococcus spp. on red and white wine;
4. Investigate factors affecting biogenic amine production by Pediococcus spp.
Approach:
Objective 1: Pediococcus strains previously isolated from Oregon and Washington wines will be used for this study as well as additional strains isolated from commercial Oregon and Washington wines. Wine samples will be solicited beginning fall 2021 from wineries who have reported or who suspect bacterial spoilage. Initial characterization will be based on microscopic examination followed by identification to species level by multiplex PCR.
Objective 2: Due the high number of Pediococcus isolates potentialy generated in Objective 1, isolates to be used for in-depth wine sensory analysis will be chosen based on an initial sensory screening. A base Pinot noir wine produced at the Oregon State University (OSU) winery in Fall 2021 will be used to screen isolates for sensory impact. Wines will be evaluated/sorted by experienced wine tasters using the napping sensory evaluation technique. This will allow quick differentiation and grouping of wines. Based on the results of the sensory screening, four Pediococcus isolates will be chosen for further sensory investigation.
Objective 3: Pediococcus isolates identified in Objective 2 will be utilized to investigate the effect of pediococci on Pinot noir, Syrah, and Chardonnay wine sensory properties. All wines will be produced at the OSU winery using grapes from the OSU vineyard or sourced from Oregon vineyards. Wines will be produced following standard practices and will undergo malolactic fermentation before being sterile filtered into fermentation vessels and inoculated with a given strain of Pediococcus at 105 cfu/mL. Bacterial growth will be monitored by plating and after an estimated 30 to 50 days, 50 mg/L total SO2 will be added to the wines before sterile filtration and bottling in preparation of sensory evaluation. Samples will be taken and assessed for basic wine parameters including acetic acid and lactic acid.
Objective 4: Wine samples collected during Objective 3 experiments will be assessed for biogenic amines by HPLC. Additional experiments will investigate the impact of substrate and lees contact on biogenic amine production. Because of the difficulty of growing Pedciococcus in model grape/wine systems, Chardonnay grapes/wine will be used. The impact of lees will be investigated by producing Chardonnay wines from previously frozen juice using standard practices. Wine will either be cold-settled and sterile filtered (no lees) or dimethyl dicarbonate (DMDC) will be added to kill microorganisms present in the wine without having to remove the lees. Additional experiments will follow a similar protocol but will investigate the addition of various concentrations of supplemental nutrients such as di-ammonium phosphate (DAP) and organic nitrogen products containing amino acids.
