Ah blueberry wine! One minute its fermenting up a storm, then next it’s a lifeless half-finished must that wont get going again. What’s really frustrating isn’t just that the old tricks don’t work – move it to a warmer room, make a fresh starter, apologizing (even if you don’t know what for) and so on – but that there was nothing wrong. It’s not an uncommon story on winemaking forums, and it happened to me recently. So what is it about blueberry wine that causes so many stuck fermentations?
It’s not Kryptonite
Or sorbate. Or any other substance in blueberries that are toxic to yeast. If there were something in blueberries that inhibited yeast, then it would become harder to ferment as you increased the concentration of fruit. 6 lb/gallon would be more difficult to ferment than 3 lb/gallon, for example, and 100% blueberries would be the toughest of all. But my own experience, and that of the only commercial blueberry winemaker I’ve talked to, is that 100% blueberry wines are the easiest to ferment.
Another thing: if it were some toxin or inhibitor in the blueberries, then it would be hardest on the yeast early on – when it’s struggling to come out of dormancy and grow. But when my blueberry wines have stuck, it’s been after a vigorous start. The large established colony of yeast then sputters at around SG 1.020 – 1.040. The question is, what changes between the promising start and the all too common fizzling out?
Win her heart with constant attention. And pH management.
The first time I had a blueberry wine stick on me, I got it going again by adding nutrient. So I began to think that blueberries were low in nutrients. You know, if adding X fixed the problem, then there must not have been enough X to begin with, right? Not so fast. I wasn’t measuring pH back then, but I’ve since noticed that pH drops to dangerous levels as blueberry wine ferments. I now believe that my nutrient addition raised the wine’s pH and that – not the availability of nutrient per se – got the yeast going again. That means you can’t just adjust the pH and other parameters at the beginning and think you’re done. You need to ensure that the pH stays optimal all the way through your fermentation.
Trouble-free blueberry wine: two ideas
I haven’t got this licked yet, but I have two things I want to try. Since there’s something about blueberry wine that’s causing stuck fermentation, blending with something else ought to help. And if I’m right about it being a problem of too-low pH, then blending with something else that tends toward high pH would help even more. Cherry wine is the obvious choice here because it settles at a high pH even when the titratable acidity is high. Like blueberry juice, cherry juice is readily available in grocery stores – it would fit right in with the easy recipe from juice that I’m trying to create.
The other idea is to keep this a 100% blueberry wine, but to attack the pH problem directly. What I want here is something I can add to buffer the fermenting wine at a higher pH. Sodium citrate or potassium citrate might do the trick. They are salts of citric acid, which is the dominant acid in blueberries, and are used as flavorings and buffering agents in the food industry.
Maybe one of these will do the trick. Maybe something else, but I feel like I’m getting close.
About the photo
It wasn’t just the color cast that made me think of blueberry wine. There’s something about the photo, from the exposure to the model’s pose and expression, that’s enticing but just out of reach. Blueberry wine can be like that. Herman Layos did a great job with this photo, and I really appreciate him making it available under a Creative Commons license – thanks Herman!
Anhydrous ammonia, urea, diammonium phosphate, and nitrogen solutions, when first applied, greatly but temporarily increase soil pH
I think the same thing can happen when we add DAP, or other nutrients, to our wine musts.