WONDER:<br>How grapes become wine.<br>Part II

How grapes become wine.
Part II

The magicians second trick.  

So the sun shines, the grapes are picked and ushered into the winery, and the miracle of primary fermentation turns juice to wine. Once the sugar is all gone, the yeast say goodbye and the bacteria say hello. This new state of transformation is called malolactic fermentation. For your mouth this means green apple into buttery popcorn, straight lines into rounded bends



Malolactic fermentation (malo) can actually begin during primary fermentation, but nothing really happens in a meaningful way until after primary fermentation stops. As the sugars are eaten and the alcohol content rises, the fermentation baton is passed to bacteria. Malolactic fermentation is, as the name suggests, a process whereby malic acid is turned into lactic acid by a family of bacteria. If you’ve ever made pickles, kim-chi or sauerkraut then this is pretty much the same kind of process, just a different type of bacteria. 

Malic acid was first isolated from apple juice (the Latin word for apple is mālum), and it’s the main acid in fruits like apples, peaches, pears and plums and the second most predominant acid in grapes after tartaric acid. The main flavour component of rhubarb is actually malic acid. So, if you can imagine that tartness, that’s malic acid in a nutshell. 

Traditionally, all wines would go through malo, but these days, while all red wines are still left to proceed through this natural process, modern conventional wisdom is that only certain white varieties, like Chardonnay, should go through, with most other white varieties (and rosé wines) stopped before it can happen, to preserve the 'fresh' and 'bright' characters that malic acid brings. Winemakers can prevent malo by adding sulphur, filtering the bacteria, keeping the pH below 3.3 with a large addition of organic acid like ascorbic or tartaric, or cooling the wine down below 14°C and holding it there. 

We love malo, so no longer ever try to prevent it. In our 2018-2021 harvests we trialled preventing malo in a few batches by keeping the wine cool after primary fermentation was complete until blending and bottling, and then running the wine through a filter before bottling, which removes the bacteria that drive the process. But over time we learned that we have more than enough natural acid brightness in all of our wines even after they've been through complete malo, so now we always just let nature be nature and flow through its natural process.


Here’s how it all goes down...


Malo is a spontaneous and natural process and it starts to really get going a few weeks after primary fermentation is done and dusted. Sometimes, malo starts early if the conditions are right, but when winter sets in and the cellars cool down then malo goes dormant. Just like when winemakers want to intervene and prevent malo they cool down the wine, well this is what winter does. Spring brings warmer weather and then the bacteria wake up and malo begins again. Sometimes we’ll even place our barrels out in the sun during this period to get things moving.




Then, once things warm up enough, the bacteria get to work. Malic acid is eaten, and lactic acid is excreted. The tart/sourness drops off and you get the buttery acid notes (think: yoghurt). That’s thanks to lactic acid. The bacteria at work here are everywhere: in the vineyard, on the grapes, in the winery and they’re in the air, so they’re inside us too. Not only does this process de-acidify the wine and provide butter/pastry vibes (think: bakery), it also gives the wine a smoother, more rounded mouthfeel. Primary fermentation is eating a fresh apple straight off the tree, malo is putting that apple inside some puff-pastry and making a delicious danish.  



As we’ve just mentioned, the mouthfeel you get from malo is softness / roundness and buttery notes. Explaining why is pretty technical, but essentially, it’s got to do with proton exchanges and changes in pH. The buttery flavour has a lot to do with a compound called diacetyl, which is what is synthesised and used to flavour microwave popcorn. True fact. On the nose, the aromatics of malo are slightly harder to predict. Different strains of bacteria can change aroma in different ways. But the common aromatic notes you’ll get are roasted nuts / dried fruits in whites and roasted/smoky/chocolatey aromatics in reds. Often though, in reds especially, malo can reduce some of the primary fruit characters.



All of our wines go through full malo nowadays. Blending malo components with just a little of a primary-ferment-only component can offer the best of both worlds; clean zippiness with textural softness and create a moreish dance in your mouth that we are always striving to capture. But after lots of trials and new learnings and experiences in Italy for Matt our head winemaker over these last years, we have learned that picking a little earlier for brighter natural acid is an even better, more traditional and far more elegant and instinctual approach to achieving this kind of dynamic mouth feel.