2014 Eastern Winery Exposition: Tartrate Stabilization

We attended the 2014 Eastern Winery Exposition held at the Lancaster County Convention Center from March 3-6. My husband and I split the schedule so that we could cover the topics that were relevant and interested us. So, for the first session on Tuesday, I attended two talks given by Tom Payette on "Lab Testing Cost Analysis: In-House or Outsource" and "Cold Stabilization: Reducing Time & Energy Costs". Tom's talks reminded me of the U.C. Davis online course that I took taught by Grady Wann, called "Wine Stability". The second talk that Tom gave was about cold stabilizing tartaric acid. Tom mentioned something about "bifurcation" at a certain pH and his talk reminded me of how much I have already forgotten. So this morning, I dug into my pile of notes and located the lecture on tartaric acid. I think it is really important to know the chemical structure of tartaric acid:

Tartaric acid is a dicarboxylic acid as shown by the red circles in the diagram above. There are 2 titratable hydrogens on the carboxylic acid groups in tartaric acid which sets up the chemical equilibrium shown below:

What we really care about is what is happening to the tartaric acid in the pH range that we typically find in wine, that is between pH 3-4. The species of tartaric acid which exists in wine is pH dependent. The chemical equilibrium shows that between pH 3.1-3.5 both the free acid and its first conjugate base can occur. This equilibrium can also be visualized by the diagram shown below:²

From the diagram above, the maximum concentration of the bitartrate ion, HT^- exists at pH 3.6. If potassium is present, the hydrogen tartrate (HT^-) is present as the potassium salt, KHT. There is in wine, a high concentration of potassium (0.8 to 1.5 g/L), making wine a supersaturated solution of KHT. For tartaric acid, a diprotic acid, the crossover point is at pH 3.65, meaning that hydrogen tartrate, HT^- as it's potassium salt, KHT is at it's maximum concentration at this pH.³ The KHT (potassium tartrate) will precipitate out at its lowest solubility level at a pH between 3.4-4.0.
The pH of the wine prior to cold stabilization will have an impact on the final pH:

• If the pH is < 3.65 loss of too much hydrogen tartrate as the potassium salt will lower the pH, which is a good thing for wines.
• If the pH is at the pK of the KHT, there is no net effect
• If the pH is greater than 4, there will be a rise in the pH

The loss of 2.51 g/L of KHT through precipitation, will lower the TA by 1 g/L.
Enough chemistry! But important, don't you think. And I've figured out what Tom Payette meant by "bifuration point". Next blog will be about how to remove the KHT from the wine.

References:
1. The chemical structure of tartaric acid was drawn by the freely available drawing program from ACD Labs called ACD/ChemSketch Freeware.
2. Bruce Zoecklin, A REVIEW OF POTASSIUM BITARTRATE STABILIZATION OF WINES, Virginia Cooperative Extension, Publication 463-013, 1988.
3. Organic Acids in Wine.

Wine Tasting at Waltz Vineyards

We've been on a road trip to Lancaster, Pennsylvania since Monday of this week to attend the Eastern Winery Exposition. More on this later. On our way home, we stopped in Manheim, Pennsylvania to go to Waltz Vineyards to taste Jan and Kim Waltz's wines. We've been tapping into Jan Waltz's extensive knowledge and experience of growing vinifera grapes in the northeast, but never tasted his wines, so this was a perfect opportunity. We were met in the tasting room by Lea. She explained to us how the wine tasting is conducted at Waltz. The offering was divided into "Light and Fruity" and "Dry and Serious" tasting flights or we could choose any wine to drink by the glass. I opted for the "Dry and Serious" and my husband went for the "Light and Fruity". Before coming to the winery, we met Jan at the H&W booth at the Eastern Winery Exposition and he mentioned that their tasting is a little different from the norm. Their flight would come in test tubes and we could sit and sample the wines at our leisure. That sounded very interesting.

We did indeed taste the wines leisurely asking Lea many questions which she fielded expertly! Although the flights are separated into "Light and Fruity" and "Dry and Serious" all the wines are made true to variety and are all serious wines! We left with a case of wine to share with our friends back home. If you live in Pennsylvania or any where close to Manheim and love wine, you must put this winery of your list of destinations, it is well worth the trip!

Champagnes Aubry and Pierre Péters

We welcomed back our friend who was in Sochi for a month with a degustation of Champagne and oysters. For this evening, we cued up two Champagnes both of which were récoltant-manipulant, that is a grower who makes champagne from his own grapes.
The first one we opened was this Aubry Brut Premier Cru, made from a blend consisting of 45% Pinot Meunier, 25% Pinot Noir, 25% Chardonnay, and 5% of the ancient varieties Arbanne, Petit Meslier, and Fromenteau. We could taste and appreciate the complexity of the Champagne which we were drinking with Long Island blue point oysters and Moonstones from Point Judith, Rhode Island.

The second Champagne that we opened was this Pierre Péters. This Champagne is a blanc de blanc, made if 100% Chardonnay and had a beautiful floral nose. The Pierre Péters and the Aubry are Terry Theise Estate Selections imported by Michael Skurnik Wines Syossett, New York. So, a side-by-side tasting was in order! So with two glasses each, we were able to taste how each Champagne paired with the oysters. Another thing that we are trying to do with the Champagne tastings is to find the perfect bite. Our friend Mary brought a contribution that stood up very well to the acidity of the Pierre Péters, it was a delicious bite of Soppressata Bundles with Radicchio and Goat Cheese.

Integrated Pest Management (IPM) in the Northeast

I discovered that a really good place to begin learning about Integrated Pest Management (IPM) in the Northeast can be found at the Cornell University New York State Integrated Pest Management Program. This is a site tailored to IPM for grapes. Topics covered include:

• Dormant IPM practices to be implemented
• Vineyard Mapping
• Pruning to Reduce Overwintering Disease Inoculum
• Grape Berry Moth Weed Assessment Protocol
• Weed Management
• Grape Facts: Managing Weeds in New York Vineyards

This site also contains a link to NYS IPM Fact Sheets for Grapes, that is a great resource for learning about grape pests as well as grapevine disease including downy, powdery, black rot, and more.
Another really good reference to have is A Pocket Guide for Grape IPM Scouting in the North Central and Eastern United States. Reading the literature and familiarizing ourselves with the IPM for the upcoming season is what is keeping us busy as the wind howls outside. Shouldn't it be spring already?