buttery malolactic fermentation

Close encounters of the malo kind

For this next installment of The Winemaking Diaries I want to introduce you to fermentation.

Hang on. We covered this last time right?

Well sort of. We looked at alcoholic fermentation, but that is not the only type of fermentation that can occur when it comes to wine. There is a second kind of fermentation too called Malolactic Fermentation (MLF or ‘malo’ for short).

This is the process of converting harsh malic acid – the type you get in green apples – to softer lactic acid which is found in milk.

So what gives – why do wines undergo both fermentations?

Well firstly, malolactic fermentation is a natural process, so unless the winemakers actively try to prevent it then it’s likely to happen. It has many merits as it:

  • Adds a rich, buttery character to a wine
  • Adds body
  • Helps to stabilise wines (particularly reds)
  • Helps to integrate oak and fruit character for a more seamless wine

Sounds great, right? Well there is a slight sticking point… Not all wines (particularly whites) are benefited by this process.

Take your average Sauvignon Blanc, or a Riesling for instance. These wines are best when they are fresh and fruity in style and would be spoilt if they underwent MLF.

Therefore on occasion winemakers need to block malo so it doesn’t happen. The great thing is the solution is simple. You see, malolactic fermentation needs warm temperatures (min 15C) to start, so if you chill down your vat of wine and chuck in some extra sulphur dioxide then you can prevent it.

Pretty much all reds will undergo MLF and some whites too. Chardonnay in particular benefits hugely from this process, so next time you try a big, buttery chardonnay you will know it’s all down to malo.