2018-2019 Group Projects

Protein Stability

Many of the white grape varieties grown in Virginia contain high protein content. With the rise of CMC for tartrate stability, it is more attractive to get wines protein stable before bottling, but that often includes a level of bentonite that may also strip flavor. This study aims to remove protein using protease enzymes, tannin, and bentonite at the juice stage, before flavors are released during fermentation. The protocol includes fermenting on bentonite, so this is not a suitable protocol for wines that will be aged on fermentation lees.

 Viognier, Sauvignon Blanc, Petit Manseng, Traminette, and Rose would all be welcomed for this trial.

Petit Manseng Harvest Decisions

Harvest decisions for white grape varieties are often based on sugar and acid, but Petit Manseng has a different balance of these components than most varieties grown in Virginia.  The idea of this trial is to harvest at “low”, “medium” and “high” brix levels and take each lot through to finished wine. If the participating winery has limited capacity, the trial can be limited to “low” and “high” levels. Sensory analysis will focus on the balance of alcohol, acid and flavor as well as stylistic differences between ripeness levels.

Harvest Decisions based on Phenolic Ripeness in Red Wines

Harvest decisions for red grape varieties are based on many factors including wine style, lab measures like brix and acid, vineyard observations, and flavor. Another marker of ripeness is phenolic maturity. Unfortunately phenolics sometimes reach a maximum then begin a decline before brix measurements level off, leading to loss of phenolics in the vineyard. This study will utilize berry sampling over time to assess phenolic development as a means to provide an additional parameter for picking decisions. Done in conjunction with Enartis, each block will be harvested twice, once based on  a prediction of phenolic maximum, and once based on the winemaker’s normal practice.  This study requires the ability to harvest in smaller picks, with only a few day’s notice. Analyses will include full wine chemistry including tannins, color, and sensory analysis.

For an example of the type of data produced, see King Family’s Cabernet Franc trial from 2017.

SO2 Management during Red Wine Aging

Once wines have completed fermentation and entered aging, SO2 is used to prevent microbial spoilage and oxidation. However, a survey of winemakers reveals several philosophies for managing SO2. Some add one large dose after malolactic, allowing the free sulfur to drift down until bottling. Others add a smaller dose initially, with several additions through aging. This study aims to compare both approaches, focusing on the effect of SO2 management on phenolic development, microbial growth, and production efficiency. This study will include two treatments, one with a 75 ppm dose after completion of malolactic fermentation, one with 30 ppm.  SO2 will be checked and kept at a target molecular SO2 of 0.5 mg/L during aging. This experiment is done entirely after harvest and requires periodic SO2 monitoring.

Lees Stirring in Aging Wines

Yeast cells contain mannoproteins and other factors that are released over time as cells autolyse.  These compounds can be used to round out or soften the palate of the wine. Several VWRE studies have explored stirring of yeast lees with inconsistent results potentially due to insufficient dose or insufficient time to see an effect. There are two approaches we would like to explore:

(1) A  natural lees addition of up to 5 liters with extended time (up to 6 months) of weekly stirring.

(2) Addition of an “activated” yeast product that is meant to break down faster (3-4 weeks) for earlier bottling wines. 

Participants can choose to do one or both treatments along with a control. Preferences might be different for different styles and types of wines, so a large sample pool is preferred. This trial is done entirely after malolactic fermentation and, once additions are made, only requires stirring once a week. 

If you are interested in participating in a group project, please let us know before July 2.  Click here to sign up, or contact Joy Ting at VaWREx@gmail.com.