Yeasts of the southern wild

It’s been a week since I posted last, but harvest has been so hectic that I haven’t had a chance to sit with my computer and write. It’s been 13-16 hour days with a couple 4 am starts, so both my mind and body have been prioritising sleep over blogging. Nevertheless, since then we started fermenting so many tanks of must by adding yeast to them (the actual ‘wine’-making part) I thought I’d write a bit about the topic.

Yeasts are magic. They are the ones responsible fermenting what is essentially just grape juice into an even more delicious alcoholic beverage that people buy to celebrate or unwind with,  to drink when they’re happy, sad or fighting global wars (like Madame Taittinger and Churchill respectively) and generally obsess over.

Reading about wine-making before, I never really gave much thought about yeast. I didn’t realise just how many types of yeasts there are. There are yeasts for all occasions and wine styles, bred by companies to suit any type of need -slow, fast, hot, and cool fermentations, and ones that impart certain flavours to the final wine.

What’s interesting about it is that although it seems quite complex, the process of adding yeast to must to make wine is very similar to that when you prep it for baking bread. It actually looks and smells the same – miniscule sandy-coloured pellets when dry with a bready and beer-like aroma. To proof it for a vat of wine, you add hot water to a bit of grape juice to get it going. Warmed up and active, they start bubbling away quickly and create a nice warm foam floating on top of the juice that you have to stir around with your hand. Laura took quite a fancy to this, and it does feel pretty nice, although your hands smell like yeast for the rest of the day.

For white wines, before fermenting with yeast, you crush the must, press it to remove the juice from the skins and grape solids. Then you settle it so any remaining solids float down on the bottom of the vat and can be removed before adding the yeast so essentially you ferment it as a clear juice. You make up the yeast separately in a bucket and climb a ladder to pour it into the vat from the lid on the top.

A yeast culture for white wine that just started proofing, and then the same yeast 5 mins later

For reds, you actually crush the grapes and leave them in a vat with the berries and skins and then add the yeast to ferment. This helps extract colour and flavour from the skins, so that the juice has all that lovely red wine aroma and tannin that comes from the skins. Adding red wine juice to the yeast to activate it makes it looks a bit like strawberry yoghurt! At Jordan, we add the yeast when the red must is being pumped over, which is basically circulating it by drawing it off the bottom of the vat and pumping it over to the top so it sprays down and mixes again with the must. It’s a messy business, and you get splattered with red wine droplets all over any exposed parts of your body. Red juice beauty spots are a common sight amongst the team.

 

 

 

Red wine yeast-making, pouring juice into the yeast to 'feed it' during proofing, and Mike watching over a pump over process for Merlot

 

Apologies for the fuzzy pictures. Took them on my old iPhone in the cellar as having a camera around is a bit risky with all the juice droplets flying around!

Measure for measure



Log books we keep for science

I’d like to think that my personality traits of being precise, careful, and consistent were what made Sjaak and Jolette pick me as the designated lab analysis person on the team, but it’s more likely to be the fact that I’m a massive nerd. Geek tendencies unleashed, I realised that I do enjoy the lab work a lot, and will be further encouraged as I write this post about science.

People tend to think that winemakers go out amongst their sunny vines, pick a few ripe, glistening grapes and pop them in their mouths and think, ‘ah, now is the right time to pick’. It is true that tasting grapes is a way to gauge the right time to harvest them, as this gives you get a sense of the qualities of the fruit, but a crucial consideration for wine-makers is predictability and consistency. There is a discipline around trying to avoid a disappointing or faulty finished wine. This is when science and relentless measuring come in.

Lab work generally falls under three categories of testing: measuring the sugar levels, pH and acidity.  These things must all be at the right levels and balanced between them to make the resulting wine also balanced, and thus pleasant to drink.  Wine-makers will run tests on the grapes before they harvest them, on the grape must after crushing and pressing, and before, after and during fermentation and bottling.  Basically, wine-makers have to be as obsessed with measurements as the contestants on ‘The Biggest Loser’.

Sugar levels determine a wine’s eventual alcohol level, its mouthfeel, and also how balanced the wine is with its acidity. At Jordan, we measure sugar levels using a ‘Balling’ (aka ‘Brix’)  meter, which gauges the density of a liquid. Sugary liquid like crushed grape must is denser than water, so by putting a Balling meter into it and seeing how much it floats will indicate how much sugar there is in it. The sugar levels will drop after you add yeast to start fermentation, as yeasts will feed on the sugar in the must to produce alcohol and carbon dioxide. Like humans, they’re carb-loving and greedy, and will eat all the sugars in the must until there is none left and they kill themselves, so it’s crucial to see where they are in the process so that you can stop fermentation or let it go on until the must (which is now considered ‘wine’ as it’s alcoholic) is completely dry and has no sugar left. These Balling meters are super-delicate, and after a spate of a few broken ones, Jolette started a campaign to 'Save the Balling Meter' and seriously considered making picket signs.

Balling meter in action

We measure acidity by doing a titration, which flashbacks to high school chemistry class. You see how much acid there is in grape must or a wine by adding a basic solution slowly to it until it becomes neutral (equally acidic and basic). We add an 'indicator' solution to the sample, which is basically like a dye that turns pink when the liquid is neutral. Then you measure how much basic solution you used to do this, as that will exactly equal how much acid is in the grape must or wine.

The sample on the right has been titrated to neutral...hence the pinky colour

We measure pH using a handy device – a pH meter, which is beautifully simple to use. You stick the probe into the liquid and press a button and it’ll read the pH. Although pH is an indication of acidity, it also takes into account the effect that natural salts, potassium found in grape skins which affects the acidity, and also its colour, taste and keeping levels (David Bird, ‘Understanding Wine Technology’, 2000). It’s in essence a more accurate indicator of how a wine will behave and how we will perceive it to taste.

 I start each day taking sugar level readings of all the tanks with fermenting must with the Balling meter (19 tanks today). Also if the vineyard team wants to test the ripeness of the grapes on the vines to decide when to pick, they’ll also give us bags of grapes which we will have to crush by hand to get the juice for the acid, pH and sugar readings before Gary, Kathy, Sjaak and Jolette taste the juice. The lab is an oasis of calm amongst the loud clanking of pipes and the screeches of the presses, and is a nice way to start the day. However, it can get a little crazy, like when we had fourteen grape samples to do and I was running around like a mad person on speed!

Squishing grapes from the vineyard to test them in the lab. A sentry of samples in jugs ready to be tested