Over my last few batches, I've had problems with diacetyl in the finished beer. I've been all grain brewing for about 6 years, and diacetyl hasn't ever been a problem until recently. I'm trying to figure out what may have changed in my recent beers, and I've narrowed it down to two options: 1) The use of acidulated malt 2) Use of a stainless conical
I recently purchased a pH meter, and, as a result, have been paying more attention to the mash pH. I've been adding acidulated malt to get the mash pH to the 5.3 - 5.4 pH range. This has required the use of 2-4% acidulated malt in the mash, which I think may be the problem. The final beers, once the hops begin to fade, have had either a strong buttered popcorn aroma and flavor (in the earlier bad batches) or a stronger than expected caramel/toffee flavor (the most recent batch). The most recent batch had no "traditional" crystal malt in it - only two row, white wheat, and carafoam.
I've also recently started fermenting in a conical. I really don't believe this is the cause, since I've fermented the beers, all using Cal Ale 001, at 65F to 68F with a raise to about 71F at the end to push the yeast to finish their work.
I've bought new tubing for transfers and I have no reason to believe my sanitation is the cause. I keep coming back to the acid malt, and am planning to drop it from my new batch. I'm thinking of either letting the pH go or using phosphoric acid instead.
Has anyone else has diacetyl issues that might have resulted from acidulated malt? Any other thoughts?