"Hi Shovel,
Quote:If you achieved the same outcome(SG) with both processes then why go after a longer ferment?
This is a great question. The short answer is: because the lowest FG/quickest ferment may not be goal.
If all yeast simply converted sugars to pure Ethanol (and did nothing else), then there would be no reason to prolong the process. But fortunately (and sometimes unfortunately) there's a lot more going on. The guys that really know what yeast do, and I am
not one of them, use terms like ""pathways"" and ""genomic expression"" and ""transient response"" and a bunch of other such terms that leave my head spinning. But it basically all boils down to this: yeast produce a bunch of different things during fermentation and each strain is unique. Some of those things may be good or desirable (ethanol is obviously desirable, certain congeners at appropriate levels, etc) and some may be bad (an overabundance of certain congeners). It all depends on what you're trying to accomplish.
That said, when you measure the final gravity, all you really know is the relative density of your wash compared to pure water. It doesn't tell you anything about what's in your wash. So we're left with trying to figure out
why our fermentation finished lower/quicker ... and whether or not it produced the results we want. Here's an example:
When I started out I would ferment at 30 C. I maintained the temperature with an aquarium heater. It was great (or so I thought). The fermentation was vigorous, huge krausen caps, a very active airlock and always done in seven days or less. It was great to watch ... it looked so healthy. When I ran those washes I had lots of heads. So I spent a lot of time learning how to run the column better. Then I started getting lots of compressed heads. The problem wasn't solved -- I just got better at taking off heads.
Then I started paying more attention to what guys like scotty, BR, heeler were saying about slower, cooler fermentation. I read up on the attributes of different yeast strains ... even tried to understand what the beer guys were trying to do with lagering. So I dropped the temps down to 20 (or lower), started using more ""neutral"" yeasts and things got much better. My washes now take two to three weeks to finish, but my neutrals are much cleaner now and I have a lot less heads.
And here's the trump card: my OG and FG are still the same, no change, nada.
Anyway, it took time for me to figure things out, develop some patience, and listen more closely to the guys on this forum that have been doing this for years. They're a great resource and very nice people as well.
Regards,
--JB"