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Yeast Selection in Action
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Rights, that is enough of that. On with the show.
I once got asked a question “What yeasts do you use?”, My immediate thought was “Does this person truly want to know the precice yeast strains we’re using???”. Because that’s a pretty big question. Turns out they were just pondering on whether we inoculate or whether we do ‘wild’ fermentations.
The answer to that is this:
“We generally don’t actively push for wild ferments, don’t do any ‘pied de cuve’3 or anything like that either. Although between pressing, racking and inoculation, if the juice is starting to ferment, quite often we’ll leave it for a few days and see what’s going on.
Usually if starting native, Ben will be looking at ferment speed, temperature, any signs of reduction of off-aromas. If they’re ticking along native he’s often happy to leave them, but we can always inoculate after a few days.”
- Dan Kirby, a vineyard tour at some point in the summer of 2023.
Here’s the answer to the more complicated version of the question that nobody asked for.
We Need to Talk About Yeast
I know, as many of you do that winemakers play around with different yeasts, but where’s the thought that goes into them? How long does it take to come up with a working knowledge of which yeasts go in to which wine?
What do you do when you don’t know where to start?
The MW programme is a fascinating one, the trick to it is discovering the ‘why’ behind the wisdom. To do that you need to get yourself out of the textbooks and into the mind of the winemaker. Look for what they don’t tell you in the book.
If you need some real-life examples on yeast selection, you’re in for a treat. Because, guess what I was doing last week with Oli the asst. winemaker at Flint? Yep. We were choosing yeasts for some tanks and barrels.
Here’s What We Did:
1. Make a Note of What Wine You Have
We had a range of wines, an array of Pinot Gris and Pinot Blanc press fractions to innoculate. Plus some Chardonnay, and a tank of Bacchus that had recently been racked.
The Pinot Gris & Pinot Blanc consisted of 14 x 225ltr neutral oak barrels:
4 x Pinot Gris 100% whole bunch pressed.
4 x Pinot Blanc 100% whole bunch pressed.
2 x Pinot Blanc, ‘coeur de cuvee’5 (‘CdC’)
2 x Blanc & Gris, ‘coeur de cuvee’ (Co-ferment)
2 x Blanc & Gris, ‘press’ (Co-ferment)
Yes, that’s a bit of a jumble, but we’re dealing with a few tonnes of each variety here, and were interested in separating the the 100%, co-ferments, as well as splitting the ‘press’ from the ‘coeur de cuvee’ fractions. That is just the way we like to do things.
Then we had 2 x barrels of press Chardonnay in old oak, 3 x barrels of ‘CdC’ Chardonnay in 100% new oak, as well as 2000 litres of Bacchus in stainless steel.
We didn’t think it would be a great idea to just inoculate all the same varieties with the same yeast, so we had a look at what options were available to us.
2. Review the Tech Sheets of Available Yeasts
Ben’s6 philosophy is to always experiment, and yeast is just one of the many ways that a winemaker can do that.
Just before harvest, Oli said to me he could almost start a shop with the amount of different yeasts we had in the stock room shelves. We make a lot of different small batch wines at Flint, and then we have quite a complex blending process to get those flavours balanced.
Most yeasts come in dried form, in shrink wrapped aluminium, ready for rehydration. They’ve been isolated and selected for their various flavour characters, their location in the world, likely derived from combinations of native cultures and repopulated.
The data on each yeast you get is often along the lines of Fermentation Speed, Lag Phase, Nitrogen Requirements, Turbidity preference, Alcohol Tolerance, Volatile Acidity, SO₂ Production, and Max/Min. Temperature preference. Along with some indication of flavour production and flavour characteristics, common variety combinations, country or region of isolation.
You can then take this information and decide which yeast you’re going to go with.
If you’re interested, here’s the 2020 Lallemand catalogue, to give you an idea of the number of different yeasts that a winemaker can use on their wines.
3. Get Pitching
Most of the wines we had to choose from this time around where white wines, that had been pressed straight into barrel. We knew that we didn’t intend to chill/clarify the juice, so inoculating relatively quickly after pressing was the plan.
We ended up using about seven different yeasts across all the wines. For the Pinot Gris, pressed as a white, we used a rosé style yeast. For the Pinot Blanc, a riper, more ester/aromatic driven yeast in some barrels, and a more traditional Burgundy/Chardonnay yeast in others to see if we can find a combination of flavours.
We used some non-sacc starter on some of the Chardonnay and some with that same classic Burgundy/Chardonnay yeast. And for the bacchus
I very much enjoyed a day or two of hands on, hands in7 experience inoculating ferments. The things you read in the book all fall immediately into context once you’ve actually done it. Not just watched someone else do it either.
Things They Won’t Tell You in the Book:
The Bacchus tank: I wanted to use QA23, (More on Bacchus below, you’ll see why), but quite simply, we didn’t have any left in the cupboard, so we opted for a more classic yeast for that tank. Hopefully it works out, it’s a slightly more neutral strain, but quite dependable8.
The instructions on the packet: Rehydration protocols, to re-activate the yeast, and a guide on the amount you should add to the tank to make sure the yeasts are healthy. 30g per h/l is pretty standard apparently. With one strain we had half a packet left, and for the size of the tank meant we were at 15g per h/l, so we just used what we had and hoped for the best.
You shouldn’t bring the rehydration temperature (appx 37°C) down too quickly, add cold juice from the tank gradually. If you’re faffing about with barrels of juice at 11°C, the easiest thing to do is syphon some juice out the top of the bung, and that is not on the packet. High school science in action, and a mouthful of delicious, sweet, sweet Pinot Gris.
Always use a bigger jug than you think you need.
If you look on my recent Instagram post, you can see this in action with our Bacchus.
A majority of the wines in tank as of 29th October 2023, were from just three of Flint’s vineyards, Brown’s, Plantation and Pittles. There were 12 tanks in total across the three plots, and a majority of those has different yeast strains.
Part of my role at Flint this year is doing the fermentation checks, most days while I’m there. Ben and Oli keep an eye on them, but I have to go and gather the info on everything that is fermenting most days.
After a few weeks of processing, pressing, and then Ben & Oli racking and inoculating the tanks of Bacchus, then tasting and checking the sugars most days, I can tell you categorically that a yeast called QA23 is my favourite.
X-16 is interesting, Oli wanted to try a an Austrian Riesling yeast, R-HST which is working well in barrel, we’ve got a couple that are intended to bring out some more mercaptans/thiol aromatics, and we’ve played around a bit with some ‘non-saccharomyces’ options, Kluyveromyces thermotolerans, Torulaspora delbrueckii blended with Saccharomyces, and we’ve left a few to go native as well. The idea is that all of these flavour components are able to be blended together to increase complexity and character of the final wine(s).
So there you go, after a few long days looking at tech sheets, assessing tanks and barrels, taking stock of juice ready for ferment, trying to look at stylistic variations, running some analysis such as pH, TA, YAN and sugars on the juice, the names of yeasts are rolling off the tongue, just like Fergus was, but I’ve only been doing it a day or two.
I’ve got no idea how many harvests Fergus has done, or Ben for that matter, but I’m sure in just one of those vintages, processing a considerable amount of wine, they’ve both been through more strains of yeast that I ever have.
Working in a winery is much, much more informative than visiting one.
At least I hope I don’t.
A ‘starter’ or ‘collected’ wild yeast, usually from pressing a bucket of grapes in the vineyard a few days before harvest. Ready to pitch your ferments with a ‘native’ yeast that’s already got going a bit.
‘Coeur de Cuvee’ translates to ‘heart of the press’, and isn’t the early ‘free-run’, or the later ‘press’ fraction, but the nice bit in the middle.
Witchell, Head Winemaker and MD at Flint Vineyard. My Boss.
It’s best to stir in the yeast with your hands.
Get in touch if you want to know that strain…