Well, your grape or juice source really put you in a bind. Those are some of the most unbalanced initial numbers I’ve ever seen, and I would seriously consider getting your juice from another source next year. Numbers like that — with the acid being so low and the Brix simultaneously being low may be, I hate to say, indicative of dilution with water. I really hate to propose that someone would be that unscrupulous and certainly don’t want to get anyone in trouble, but you’d expect a 4.1 pH for a red grape to correspond to Brixes being at least above 25 if not closer to 28. Like I said — whatever the cause, those are very unusual, unbalanced numbers and certainly didn’t give your project much of a starting chance.
You did the right thing by trying to add acid to make up for that dangerously high pH of 4.1. Targeting a TA of 7 isn’t a bad thought, though it’s a little high for my tastes and because of the buffering capacity of your juice, landed you with a really low pH. 3.2 is very low for a red wine and, post- adjustment with a pH of 3.2, there’s very little chance a malolactic fermentation is going to be able to happen to completion.
I think this is where your problem lies now because it’s really unlikely that your ML fermentation will happen at all. Where did the 10 g/L total acidity come from? There’s no logical reason for a TA to go up that dramatically unless the acid you added in the original hit wasn’t well measured out and also wasn’t well mixed in when you sampled and got that 7.5. This is one of the reasons why I suggest in my book, The Winemaker’s Answer Book, that such large additions are best made in at least two stages, so that proper mixing can happen.
Salvage? It’s hard to say what I would recommend because this poor wine has been through so much already and it seems to me just didn’t have a very good start in life. You could try adding potassium bicarbonate to raise the pH. I would start with 0.4 g/L, dissolve the powder in a small amount of water, then mix it in well with your wine. This should increase the pH maybe up to 3.3–3.4 . . . measure pH again and see where it goes. It’s impossible to predict the exact effect because the impact on pH with any acid addition or acid neutralization isn’t linear and is dependent upon a myriad of factors within each wine, sadly few of which are measurable. For this reason, when dealing with pH or TA shifts I always try to do bench trials on small samples first, measure and taste the results, and only scale-up to cellar batch-size after you know what the result will be.
With a pH above 3.2 you have a much better chance of at least being able to complete the ML fermentation. Getting the wine racked, SO2’d, and protected from spoilage will help it come to a point where you can begin to consider what to do with it. If you still want to try to achieve a red wine style, you might want to try de-acidifying more if further adjustment is needed. Because I suspect you’ve not got much in the way of ripe tannin, fruit, or mouthfeel, you can try to build those up using oak chips or some of the liquid oak tannins that have been launched in the marketplace in the last five years or so. Sadly, these additives and aging adjuncts can only take you so far as I suspect that your original material was compromised from the beginning. It’s impossible to replicate the richness and density, especially of a big red grape like a Petite Sirah, when there’s nothing there to begin with.
To improve the situation in the future, I think you really should consider changing your raw material sources. I also grow grapes and if I had delivered grapes with those numbers to a client, they could’ve refused to take them, or could’ve demanded a discount, as long as our contract had quality stipulations. Typically, grape contracts will have provisions that say the grapes will be above 24 °Brix or something along those lines. I know that the world of home winemaking is a little different than a commercial operation but you shouldn’t have to stand for poor quality, especially if it’s something you’ve paid good money for. Mother Nature is a fickle mistress and we all know that batches vary from year-to-year and we winemakers have enough challenges already, but it’s really a shame that Petite Sirah was marketed with initial numbers like that.