Authors Note: This blog post and vlog were created prior to the U.S. outbreak of COVID-19. The material covered here is based on observations, projects, and interactions with wineries prior to the various state orders to address the ongoing COVID-19 crisis. For more information pertaining strictly to COVID-19, please see past blog posts.
Welcome to my first installment of DGWinemaking’s Quarterly Winemaking Observations. This is a relatively new thing I would like to try and you’re welcome to watch the short 5-minute video, below, or read through my transcript on some of the top issues, challenges, or trends I’m noticing among wineries across the U.S. at this given time. Furthermore, within each section, you can find resources and links available through DGWinemaking or on the web to help you tackle each one of the topics.
If at any time you have a question, a topic of interest, or would like more information on getting help at your winery, you can contact me directly at [email protected] or DM (direct message) me on Instagram to my handle, @dgwinemaking.
Let’s get started!
We’re into the first three months of 2020, and there are a few commonalities I am seeing among clients and wineries outside of the DGW Community:
High Incidence Rate of Hydrogen Sulfide and Reduction
The first is that I am noticing a higher incidence of hydrogen sulfide and reduction in wines produced from the 2019 vintage. Now keep in mind most of these were probably linked to an inability to measure YAN or yeast available nitrogen. So if you are in that boat, then make sure you check out some of my resources below. They will give you pertinent information about measuring YAN, why to do it, and why it’s important in minimizing the risk of hydrogen sulfide development.
In a few cases, I will admit that the H2S or reduction came from another source that was not related to the YAN. This happens sometimes. You’re not alone. In those cases, please make sure to check out some of my remediation techniques. Of course, there is always copper treatment and a lot of my clients will know I also help them reduce the amount of residual copper that remains in the wine for bottling to try to maintain stability and quality for as long as they can once that bottle hits the shelves.
There are other techniques for reducing hydrogen sulfide and reduction aromas. Some of the enological suppliers will sell different products to address this need. You can also look at using lees stirring if you have fresh clean lees, especially if you noticed this technique helped in the past.
Does the wine have hydrogen sulfide or reduction? If you are not sure, the first step is getting a confirmation. You can do this by sending the wine to an analytical sensory lab or contacting Denise ([email protected]) to set up a sensory evaluation.
Once you know whether or not you’re dealing with hydrogen sulfide, then the wine should be treated accordingly and prior to bottling.
If you’re not measuring yeast available (or assimilable) nitrogen (YAN), then getting comfortable with fermentation nutrition strategies is the BEST place to start to tackle avoidance strategies with hydrogen sulfide development. For a limited time, the Article, “Fermentation Nutrition: What to Know and Why” is open for public access! This Article explains when and how to measure YAN, understanding YAN values, other factors that can contribute to fermentation, and quality risks associated with three different YAN scenarios. To supplement the section on understanding YAN values, check out the YAN Calculation Worksheet, which is accessible by anyone reading this blog post. If you need help learning how to calculate YAN, then this worksheet is for you!
DGW Clients receive several Cellar Tools to address yeast nutrition and hydrogen sulfide or reduction remediation. Clients can access Fermentation Nutrition Strategies, a how-to on when to treat your wines with nitrogen during primary fermentation.
If you have good fermentation nutrition practices, then there are several ways to test for and treat hydrogen sulfide/reductive wines. Start by reviewing your options on how to treat reduced wines. While copper treatment is common, it is not the only solution. Those without a DGW consulting package can also ask their enological suppliers for potential new treatments.
If you are using copper sulfate, make sure you complete a copper screen and copper sulfate bench trial (insert) properly before treating the entire volume of wine. Remember, it is ideal to treat the wine with the smallest dose of copper that eliminates the reduced aroma. Sometimes, added copper exceeds finished-bottle rates (outlined in the Code of Federal Regulations, or CFR). In these cases, there are options for reducing copper in wine, and the DGW Community contains a Standard Operating Procedure (SOP) for dry yeast fining that may be helpful.
Have some winemaking texts at the cellar? Both Monitoring the Winemaking Process from Grapes to Wine: Techniques and Concepts by Patrick Iland and others is a great resource for treating reduced wines. If you want something more technical, turn to Bruce Zoecklein’s Wine Analysis and Production text.
High pH in Wines
The second trend is high pH wines. I’m seeing this in both red and white wines in regions I wouldn’t especially expect high pH to exist. These are wines where the pH is above 3.80 by the time primary fermentation is done and they may go up and over 4.00 by the time malolactic is done. Now in most of these cases that I’m noticing it, the grapes or juice did not give any indication that the pH was going to be that high by the end of primary.
In this case, it’s probable that these causes of high pH are linked to high potassium retention in the fruit. Unfortunately, that’s a viticultural issue to address. But, I’m dealing with it on the winemaking side. So instead, what I’ve provided you in the notes below, are ways to identify if you are dealing with high potassium in your wine. The first step is getting your current wine tested to see what the potassium rate is because that potassium concentration can buffer the pH and causes these inflated pH situations that make it very, very difficult to properly stabilize and maintain wine quality.
Until potassium levels in the fruit can be reduced, winemakers have to find ways to manage the retention problem. If you are dealing with high pH wines (both reds and whites), I would recommend finding out how much potassium is retained in your current wines.
You can do this by sending out wine to a wine lab, like Enartis Vinquiry (under ‘Metals’ in “Wine Analysis”), to test the potassium concentration. This will help you rule out whether or not potassium is contributing to your high pH problems. Normal potassium ranges in wine are 860 – 1,279 mg/L K+ (22 – 32 mmol/L) (Somers 1977, cited by Mpelasoka et al. 2003), while high potassium concentrations range from 1,056 – 2,776 mg/L K+ (27 – 71 mmol/L) (Somers 1975, cited by Mpelasoka et al. 2003).
If you establish that potassium could be a contributor to high pH problems, you can refer to this article I previously wrote for Wines & Vines (note: click on the “Full Article” link to open all content). It may also be helpful to use a winemaking consultant for further help and guidance as dealing with high pH wines can be difficult.
The high pH wine problem can be elusive, especially if grapes come into the crush pad within normal pH ranges. The winemaker (or consultant!) doesn’t notice a problem until after the grapes have been fermented into wine, or until MLF is complete.
Several years ago, Dr. Tony Wolf revised potassium fertilization recommendations for vineyards growing wine grapes in Eastern North America. If you have a copy of the Wine Grape Production Guide for Eastern North America, you should print out this revision and add it to the book. Potassium retention in the fruit needs to be addressed in the vineyard over the course of time.
Stability Issues in Wines after Blending
And then the third issue that I’m seeing are post-blending stability issues. So where this is becoming a problem is where the wines go through cold stabilization and protein stabilization, and then later in production, before the wine is bottled, the winemaker may opt to do some blending. It’s important to remember that when you blend wines it can change the stability properties of those wines. Even if both wines were cold stable, let’s say, blending them together can cause some acidity changes that may render them unstable, and therefore, the wine could throw tartrates. If you are blending after these stability processes, make sure you are retesting the wine to ensure your stability properties are still stable.
Still stuck on this concept? The Darn Good Winemakers have spent the last three months diving into both cold and protein stability. We’ve discussed best practices, testing methods, and when to address these processing steps. This monthly forum is a great way to learn AND get the opportunity to ask your questions in how these steps apply to your operation.
Plus, DGWinemaking Clients have access to testing protocols for stability tests:
There are also checklists that provide a timeline for when to treat the wines for various steps in production. These timelines are altered for white/rosé, red, and formula wines. Remember, access to most of the website content is $100 a month for a DEMI membership. If you’re looking to improve your cellar techniques, inquire today at [email protected].
Mpelasoka, B.S., D.P. Schachtman, M.T. Treeby, and M.R. Thomas. (2003) A review of potassium nutrition in grapevines with special emphasis on berry accumulation. Australian Journal of Grape and Wine Research. 9:154-168.
Somers, T.C. (1975) In search of quality for red wines. Food Technology in Australia. 27:49-56.
Somers, T.C. (1977) A connection between potassium levels in the harvest and relative quality in Australian red wines. Australian Wine, Brewing and Spirit Review. 24:32-34.