Sugar, Acid, pH: Why you Care




So, we’ve established that it’s harvest time and talked about the importance of hangtime – getting the grapes in at the right time – but haven’t said too much about the role of the sugar, acid and pH in your glass of wine.  

I wrote a fairly detailed article about this for Snooth, so I’ll just go over it once, lightly here today. 

Sugar (Brix): As you know, the sugar converts to alcohol during fermentation so it’s pretty-darned important. The predictable outcome at the end of fermentation is that just over half the sugar converts to alcohol. So, if the winemaker picks grapes that are 24% sugar (or 24 degrees brix) he can expect to end with about 13 or 13.5% alcohol. 

Alcohol gives wine most of its body or weight. A Cabernet from a poor growing season that’s low in alcohol will probably feel rather thin and unsatisfying on the palate. On the other hand, if the alcohol is too high the heat may tickle your nose or feel really hot on your palate. It’s not supposed to draw attention to itself – it’s just supposed to be there. High alcohol also gives the wine a sense of sweetness. 

Acid: Maybe the term isn’t attractive to you. It makes you think of battery acid or something awful like that. But when it’s balanced with the other components it’s an incredible asset. It keeps the color bright, makes even a full-bodied style seem lively, helps the wine to age and makes it food friendly. In the vineyard, as the sugar goes up, the acid goes down. In a warm climate, like Napa Valley, we worry about not enough, which can make the wine flat tasting – doesn’t leave you wanting that next sip  – and short lived. No one talks about it, but wineries routinely adjust the acid in the cellar. Cool climates worry about painfully tart acidity. So, again, it’s a question of balance. 

pH: This gets into kind of geeky territory but here goes. Measuring the pH is kind of like checking for the strength of the acidity. It has a lot to do with the health and stability of the wine. 

On the pH scale, zero is acid, seven is neutral (like water) and 14 is alkaline. Most wines fall between 3.0 and 4.0. In a warm climate, if the pH gets too high the wine becomes a friendly environment for bacterial development. Fortunately, spoiled wine isn’t harmful. However – it’s offensive!! The High pH wine doesn’t hold its color well and browns easily. It’s hard to find anyone to say anything negative about low pH but, again, the wine needs to be balanced and you don’t want to feel like you’re sucking on a lemon with that first sip! 


Of course, flavor over-rides every other consideration in deciding when to harvest (at least for fine wine).


And, as I’ve said Napa Valley is on track for an excellent harvest. The weather’s been just about perfect so far. 


Those who produce sparkling wine, Sauvignon Blanc and Pinot Noir can already declare a good vintage. Lots of Chardonnay is being picked right now, under excellent conditions, so it looks good for Chard, too. For the rest of the varieties we’ll soon see… 
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