Ask Mr. Wizard

Always Question Your Instruments: III



I received this phone call a little over a year ago from a colleague. This sticks in my mind as a perfect example of a technical problem that is presented with just enough bias to lure the most suspicious fish:

I just had a question from a customer about a major problem with a whiskey fermentation. The mash was made of 45% distillers malt and 55% flaked corn, which the distiller boiled just to be sure the starch was gelatinized, the mash thickness was 3.2:1, and the mash was held at 152 °F (67 °C) for 90 minutes before cooling to 80 °F (27 °C) into the fermenter when yeast was pitched. The problem is that the fermentation seems to be over, but the final gravity is way high. The distiller is pretty sure the malt was low in enzymes. Any other ideas?

On the surface, this question looks like a no-brainer. Of course the enzymes in the mash were deficient, right? 55% enzyme-free adjunct, longer than normal mash at a moderate temperature perfect for
Response by Ashton Lewis.