The Diacetyl Debate

When I was a kid there was no such thing as the healthy heart tick – we grew up on dairy products. With potentially average ingredients or limited cooking expertise, a glug of cream or a chunk of butter was the saviour of a meal. But back then, even people with access to great produce and Cordon Bleu expertise bought into the dairy delirium.

Nowadays, while I still enjoy the odd artery-hardening mushroom sauce on my steak – more out of nostalgia than anything, I have far more appreciation of the full spectrum of fresh, natural ingredients. I consciously choose seasonal produce where possible and cook to elevate natural flavours and textures rather than mask them.

The same can be said for my taste in wine – chardonnay in particular. Back when I first started making wine, if a chardonnay didn’t ooze butterscotch, or wasn’t oaked to within an inch of its life it was considered a dud. Subtle, it was not.

While there is still very much a market for this style of chardonnay – indeed, what the consumer wants, the consumer gets – I think it’s interesting to understand what you are drinking and what its limits are.

Chardonnay is a relatively neutral grape, often called ‘the winemaker’s grape’ for its reliance on winemaker intervention. The butterscotch character that is often present on the palate is actually the result of bacteria doing the tango during fermentation.  The resulting compound is called diacetyl, which occurs during the winemaking process and can be manipulated. It is not, as some consumers think, a primary character such as fruits or herbs, imparted by the grapes. For many commercial chardonnay producers this is good news. Diacetyl (along with oak) comprises the

‘creamy sauce’ that helps disguise a lack of flavour and texture in over-cropped chardonnay. In this sense, diacetyl can be an indicator of quality – or lack thereof.

Diacetyl is also unstable, which means it can transmute over time. Most commonly that change isn’t for the better and can lead to unattractive characters (think sour milk). In fact, the presence of diacetyl – along with a few other key factors – is a fairly reliable litmus test for how well a wine will age. Highly commercial, over-cropped wines won’t age well regardless, but the existence and / or enhancement of diacetyl expedites that decline – even in premium wine.

At the fine wine end, where site expression and longevity are prized, there has been a conscious move towards minimising diacetyl in Chardonnay production, either through choice of bacteria strain and / or extended contact with lees. It will be interesting to see to what extent this trend is adopted by commercial chardonnay producers, bearing in mind the important cosmetic effect of diacetyl on otherwise lacklustre wine.

As with all things wine, subjectivity reigns supreme. So if it’s butter bombs you love, enjoy them in their youthful creaminess and save the more mineral numbers for the cellar.