Winemaking Spooky Moments

Pumpkins and corn, grapes and vines. The final days of harvest are upon us!

Is it any surprise that Halloween and winemaking happen around the same time of the year? This Halloween, it seems apt that I should share three spooky moments of winemaking and the tricks to get out of them.

Halloween and winemaking

Spooky Moment #1: Starving Yeast

Two years ago, I was working on my second vintage. While my first vintage was part of a class, this was the first time I made wine with the training wheels off. I was in charge of the yeast, nutrients, and chemicals to ensure good sanitation and health for the fermentation process.

Healthy starter

It had been a year since I had prepared a yeast starter. (The downside of a once-a-year hobby.) I activated the yeast with warm water and nutrients, paying close attention to temperature control. To the hydrated yeast, I then added crushed grapes (known as the "must" in winemaker speak) diluted with an equal amount of water. The idea was to whet the appetite of the activated yeast several hours before introducing it to the eventual feast of grape-y sugary goodness.

While I thought I had kept good notes from my first vintage, it became clear that I missed some details. Important details. Like how how much must mixture I should add to the starter.

Starving yeast

I returned home from my day job to find the sad state that was my yeast starter. Instead of being round and full with tiny air bubbles, the starter was straggly and almost lifeless. Clearly I did not add enough must mixture. The yeast did not get enough sugar and was starving.

The Trick: Thankfully, it was early in the fermentation process, literally two days after harvest and crush, and this was highly recoverable. As long as there were some bubbles going on in the starter, adding more must mixture should revive the yeast in less than an hour. That was what I did and it worked. Failing which, I would have to get a new yeast starter. I added to my notes: 1 cup of must and 1 cup of water per 5 grams of yeast.

Spooky Moment #2: Rotten Eggs

Why does my must smell like rotten eggs?

H2S compound

You learn about this in class, and you are told not to panic. Still you pray it doesn't happen to you. But if you have been making wine for a while, it is inevitable.

What contributes to the rotten eggs smell is the compound hydrogen sulfide (H2S). By the time you can smell it, it typically means the yeast is stressed. The cause could be inadequate nitrogen, excessive sulfur, and/or lack of oxygen. And I believe we might have hit the jackpot on the trifecta.

• Nitrogen - Washington grapes are infamous for having a low nitrogen level. This year's particular crop had less than a third of the healthy amount of Yeast Assimilable Nitrogen (150 mg/L) for fermentation.

• Sulfur - While I had treated the must with the same amount of sulfur every year to inoculate the grapes from wild yeasts. It is possible that the vineyard had also added sulfur to preserve the fruit for the four-hour ride back to Seattle, resulting in a double dose.

• Oxygen - With the two factors above, weak air circulation and low oxygen contact with the yeast could just seal the deal for H2S production.

The Trick: First, we increased aeration with more rigorous and frequent punchdowns. We even removed the lid on the primary fermenter for several hours to improve circulation and let excess sulfur dissipate. Finally, we moved up the nutrients schedule by a day and beefed up the yeast with diammonium phosphate (DAP) to compensate for the low nitrogen level. That seemed to get the yeast going. By the next day, the rotten eggs smell was gone. Phew!

Spooky Moment #3: Sluggish Fermentation

While we fixed the H2S problem and kept fermentation going for the next few days, the drop in Brix started to slow down again at 11 degrees. (Our goal is to get to -1 or -2, which indicates that fermentation has completed.) Brix measures the sugar content in the must. Yeast coverts sugar into alcohol during fermentation. The slowdown indicates that the yeast might be experiencing stress again and might not be able to complete fermentation.

Hyrdometer to measure Brix

Sluggish or stuck fermentation is problematic. The unfermented sugar could attract bacteria. Additionally, there would not be enough carbon dioxide, a byproduct of fermentation, to provide a protective layer against oxidation. In both cases, the wine would be prone to spoilage.

The Trick: Depending on where you are in your fermentation process (high Brix or low Brix) and your winemaking skills, there are different ways to fix a sluggish or stuck fermentation. Given that we were nine days into primary fermentation and had only reached midpoint in the Brix, our best bet was to re-pitch with another yeast strain, Premier Cuvee, that is known for a fast and clean fermentation. (We normally use Premier Rouge for primary fermentation of red wine.) That was what we did, and we did manage to get the fermentation going through dryness in the next four days.

An added bonus of this second pitch of yeast is that we happened to catch the yeast starter on video, which was pretty neat!

 

My Verdict: While this is my fourth vintage, I find that I am constantly facing new challenges in winemaking and learning new things. Sure, these are spooky moments. But once you learn the tricks to overcome each challenge, you get a deeper appreciation of the process and you are rewarded with the ultimate treat! So move aside, Halloween, with your trick or treat. This is Hallowine time!