Occam’s razor and those pesky pinking polyphenols

I recently overheard, quite unintentionally so, a snippet of a conversation between two strangers at an industry event that made my hair stand on end. The content of the conversation, or at least the small part that I heard, was on the inhibition of pinking in a white wine by using a tannin, and then the subsequent failure of this approach seeing that the wine in question eventually pinked in the bottle. For some reason this incident made me think of Occam’s razor. But more about this chap and his sharp implements (and wit) later…

‘A glass of your best Sauvignon pink, please!’

I bet you a bottle of really expensive Sauvignon blanc that nobody has ever uttered the above request in a restaurant. Why? Because nobody is interested in the oxymoron that is a pink, white wine. Pinking, a fault in white wine involving the oxidation of phenolics, commonly afflicts varietals such as Gewürztraminer and Muscat varietals, seeing that they naturally have a higher phenolic content. While not particularly prone to pinking, varietals like Sauvignon blanc and Chenin blanc can most certainly be vinous party poopers when they decide to paint the town pink.

Some of the factors that increase the risk of pinking in white wine are:

• Poor pH management.
• Reductive winemaking conditions.
• High polyphenol content.
• Poor sulphur dioxide management.
• Copper and iron contamination.
• Have I mentioned poor pH management already?

Forget about an oenological magic bullet

In an oenological paradise, pinking won’t be an issue, each vintage will be brilliant, and the grapes will be picture perfect. Alas, we live in a world where mother nature is as fickle (and sometimes vengeful) as a politician seeking coalition partners shortly after a recent election.

One way to approach the pinking predicament is to consider a holistic approach. In other words, don’t depend on some magic bullet to prevent pinking right before bottling. A critically important point is to start with proper pH management early on. There is a very good reason for this aspect of winemaking being first in the bullet points above. At a higher wine pH there is a cascade of potentially disastrous events that could first lead to your wine turning pink, and then your face turning red in a board meeting. I’m not kidding, all the bullet points above are inextricably linked to each other and to proper pH management. And guess what? A very common observation during and after this year’s harvest was high pH levels…

Slay the pink away

A part of the holistic approach to solving the pinking puzzle is to use a fining agent in juice or during alcoholic fermentation. By removing enough of the pinking perpetrators, which is commonly believed to be flavonols (a subclass of polyphenols), you are pro-actively reducing the odds of pinking later on. While PVPP, a synthetic polymer, is broadly used as a fining agent against pinking, winemakers now have another option. Click here to read more about a PVPP replacement product.

Applying Occam’s razor

William of Ockham (Occam) was an English philosopher best known for his principle of simplicity. Simply put, among competing hypotheses one should favour the one with the fewest variables or assumptions. I will attempt a hypothesis on the suitability of using specific tannins to prevent pinking by applying Occam’s razor.

The use of sulphur dioxide and ascorbic acid pre-bottling is a well-known practice in the battle against pinking. But what about the use of specific polyphenols such as catechins? The online reading that I did about catechins indicate that, like sulphur dioxide and ascorbic acid, they also have anti-oxidant properties and are indeed useful when applied in winemaking.  

Without knowing a lot about the wine described in the opening paragraph and especially considering the challenging nature of the 2024 vintage (e.g., high juice pH levels), my hypothesis is that specific tannins can be used to prevent pinking, but in conjunction with a holistic quality approach.

If I may offer another hypothesis, magic bullets only work in science fiction.