Yeast Pitching Rate Experiment - A BUST
Well, I had hoped that the funny taste in the overpitch was just green character and from such a massive blow off. It is now clear that the overpitch batch is infected somehow. This yields an inconclusive result and requires a do-over. I hate to admit failure, especially to admit I managed to brew a contaminated batch.
I have been reviewing my cleaning and sanitation regimen to determine where I might have erred. The batch was brewed together, then split into three 1-gallon batches, all of which passed through the same pitchers and funnels. This may leave the splitting and measurement of the dry yeast, or the rehydration in separate bowls, as the potential vector for contamination.
What is confusing is that the prevailing wisdom is that underpitching is a higher risk for infection as the lag time leaves the wort exposed longer, before the yeast can outcompete other bacteria or wild yeasts. The overpitch batch was blowing out the airlock within a few hours... literally the shortest lag I have ever experienced. This brings up another possible vector: the bung and airlock, despite cleaning and a long soak, may be a source of contamination.
The flavor of the contaminated beer is very tart and slightly sour, leading my taster friends and me to believe that lacto took over. Anyway, this batch goes down the drain, unless someone wants a Tart and Tiny Dubbel?
As for the control and half-pitch, we found that the control beer remains green. There may be a very slight lacto infection, but it is still a drinkable dubbel. I expect it to mature - perhaps we will see the infection increase in the bottle, but not a throwaway just yet.
The half-pitch has developed the most banana character, and was the deepest and richest color. I have high hopes that this will turn out to be a decent beer. Given that all three came through the same gear, I hope the contamination doesn't show. Another one that will age a bit.
So, time to reset the experiment. At a minimum, I have learned that there are large questions regarding the pitch rates of dry yeast. Let's also hope I have learned to double and triple-check my cleaning and sanitation.
