Wed Dec 21, 2011 10:16 am
I'm gonna agree with brewinhard that replacing some extract with more simple sugar will be a good way to dry it out. Supplementing your small starter with dried yeast is a good idea, but its tough to say whether or not that would be enough (it would depend on the condition of the yeast).
I think it probably has more to do with the extract. I remember having a similar residual sweetness despite low finisihing gravity with some extract batches in the past. I figured at the time that it had to do with caramelization/melanoidin formation from having all that extract in there. What I did (until switching to all grain) was to:
1) Take extra care to make sure the extract mixed well into solution rather than dropping to the bottom of the kettle and scortching.
2) Withholding some of the extract until the end of the boil. For example, if my recipe called for two cans of liquid extract, I'd add one in the beginning of the boil, but save the last can for 15 minutes from the end of the boil. This kept some of that melanoidin formation down, resulting in lighter color, and less intense malt flavors (this the perception of less sweetness).
-beggar
Another possible thing you could do is just let your primary go longer. Sometimes fermentation will remain active for more than the two weeks, especially in a big beer, so maybe another thing to try is giving it some more time before taking it off the yeast.