Since one of the purposes of a turbid mash is to leave a bunch of starch behind for Brett to chew on during the long lambic fermentation, I was wondering how you account for this as far as how much contributes to the ABV of the finished brew. I would expect your OG to be low since you still have a lot of unconverted starch. But if you're still expecting Brett to ferment the starch, then your final ABV would be higher than predicted by your OG, right?
The reason I'm asking is because I brewed a batch of lambic wort yesterday. I didn't do a turbid mash, but I tried to approximate it by doing a short, high-temp mash on the pilsner malt portion of the grain bill. Then I did a separate steep using torrified wheat in place of unmalted wheat. I raised the temp on the steeped wort to the mid 190's, then ran off my mashed pilsner wort into it to hit mashout temps pretty much instantly. The goal is a starchy, dextrinous lambic wort without going through the whole turbid mash process.
So the one thing I didn't consider when I formulated the recipe was that I was going to have a super low OG because none of the wheat would be converted. I ended up with an OG of 1.027, which is pretty much right on the money if I hit my expected efficiency from the mashed pilsner malt, but got no contribution from the torrified wheat.
Now I'm starting to wonder whether I should add some DME to add a few gravity points, or if I should let it ride. I was shooting for the 4.5-5.5% ABV range. If I get about 50% "efficiency" from the starch from the steeped wheat then I'd be close enough to the ballpark I'm shooting for. Any thoughts?