This week I have been seeking clarity in more ways than one. Not only are we as a class, trying to turn our turbid ferments into enticing wine, but I have been planning some killer assignments. The vintage is nearly over, but the winery is still a hive of musty activity and my class wine, safely snuggled in our fridge jungle, is clearing nicely and has been subjected to some wine Chemistry.
Top 3 things I have learnt this week:
1. Wine Chemistry is so cool
Testing for sulphur dioxide by aspiration – the sample
If you didn’t already know, it is no secret that I am a bit of a nerd when it comes to Chemistry (amongst other things). I have taught Chemistry and Science for many years, but aside from a few practical lessons (heavily restricted these days), I have done very little myself. That is until I discovered Wine Chemistry.
A bit of a surprise really; I knew that the winemaking tradition would be rooted in Science, but I don’t think I realised the potential for satiating my inner nerd. These days, with the consumer demand for quality wines, Chemistry is overtaking traditional methods. The market demands consistency and of course, grapes can be anything but. The quality of grapes from one vintage to the next can vary considerably, with the weather often playing a big unpredictable part. Winemakers are turning to Chemistry to help them.
This week we were testing our wines for their sulphur content. A sufficient level of sulphur dioxide will ensure that the wine is protected from both oxidation and microbial attack. The apparatus for this test looks somewhat like you would imagine to find in a Hogwarts potions class; all coloured liquids and glass wear. See? Totally cool!
We were also testing for acidity, which has a bearing on stability too, but also flavour. I felt so at home in the lab, maybe one day I’ll have one of my very own? I’ll have to get a stuffed owl for posterity, or something.
2. Chewy Tannins
Testing for sulphur dioxide by aspiration – the result
Ever had a red wine that has left you with a kind of dry tongue and an urge to chew? Or have you heard the term ‘chewy tannins’ in reference to a wine? It is a term I sometimes use in my wine reviews. That ‘chewy’ sensation is due to another kind of chemical reaction happening in your mouth.
Tannins are very complex chemicals found in wines. They are extracted from the grape skins, seeds and stalks during the winemaking process. They give rise to the colour, aroma and astringency of the wine. Red wines have more tannins as they are fermented with the skins present.
More science
During the life of the wine the tannin structure is continually evolving. These complicated molecules are a little like Lego bricks. They can bind to themselves or other chemicals in the wine to make huge complexes. Smaller tannins tend to have very bitter flavours, which mellow as they join with others during the ageing process. Over time the complexes may get so large that they fall out of solution and are deposited as sediment.
Tannins react with proteins in your saliva, which has a drying or astringent effect. Sometimes they can have different textural effects in your mouth: chewy, grippy or even silky. They contribute a great deal to the mouth feel of a wine and are very important in wine making.
Fermenting or storing wine in oak barrels is another source of tannins for wines. However, as I learnt this week in winemaking, you can even buy tannins to add to your wine – though seems like cheating to me. On the other hand – for the environmentally conscious winemaker, reducing the use of oak, which comes from less than sustainable forests, should be the way forward perhaps?
3. Seeking clarity
Testing for sulphur dioxide by aspiration – the set up
I have written about the lure of those crystal clear, bright white and rosé wines before. There is just something so inviting about them. Well, as it turns out, that ‘sparkle’ doesn’t just happen accidentally. Much intervention may be applied to your wine during manufacture to get it from its turbid post-ferment form to what you see in your glass.
For centuries, winemakers have been using additives for ‘fining’ wine. Lucky for vegetarians, in most parts of the world (except some parts of South America I believe) winemakers have moved away from sheep blood. However (sorry vegans) milk products and egg white are still popular ingredients used to ensure that wines are crystal clear and remain so in the bottle for years to come. Synthetic additives are also used.
Wine is a mixture of thousands of chemical compounds, including those mentioned here, but also proteins. Proteins from the grapes can become unstable under certain conditions, forming a haze in the wine. Those aforementioned tannins, whilst desirable in reds, can cause yellowing in white wines. Fining ensures that your finished product has the right colour and will stay clear when bottled.
Cold stabilisation
One of the last steps in winemaking is cold stabilisation. Wine is often subjected to large temperature changes during its life in the bottle. Cooling to below zero for a period before bottling helps to remove any chemicals that are unlikely to withstand cold storage. Tests are then carried out on samples of wine to ensure that no nasty surprises are revealed as the wine is heated back up, as may happen on a hot summer’s day.
Other happenings…
Class rosé in the fridge jungle
So as I mentioned, I have started my second marketing assignment, which is an analysis of the social media presence of the Heathcote Wine Growers Association. It makes me very thirsty! I am also beginning to prepare my final report about the production of my class rosé and a presentation to accompany the tasting of my wine.
We very nearly began making a batch of Pinot Noir this week, but we are moving house so decided that the timing could not have been worse. I hate to imagine the mess 20 Litres or so of fermenting wine could make in a moving vehicle. Making another rosé, our other option, did not seem to do the grapes justice. Also the weather has really taken a turn towards Autumn here in Melbourne and I feared for the grape quality.
Next week
We continue to put the wines in the winery through fining and stabilisation trials. I will also be attempting to make some more headway with these big assignments. It is almost time to think about trying to get an industry placement for vintage 2018 too!
Thank you for reading.