[quote=“Denny”][quote=“Chris Roe”]Denny - I hope you didn’t read my question as being hostile - just trying to understand…
Are you certain the starter is OXIDIZED??? …I know in my field of work, a lot of people confuse “correlation” with “causation,” so I’m just trying to avoid that for myself and my understanding.
Because I am using straight DME for my starter, I fully expect that my starter wort would have a different taste than my “beer” wort. With that said, yes, I can see if I added 20+% “other” liquid (1 gal +) to a 5 gal batch, the “other” liquid could start to impart other flavors, but I would imagine that nearly ANY liquid you added in that quantity would change the flavor of the finished beer.
In your experience, where do you believe the oxidation comes in? Could it come in at the “crash” phase in the fridge? …cooling temps would lower pressure inside the flask, causing outside air to be pulled in through the plug. O2 could come in that way, but - how long does it take wort to oxidize? If folks dropped the temp of the wort significantly prior to pitching, then mixed the solution vigorously (thereby mixing in the new O2 into the wort), that would be a way to get oxidation I guess, but - again, how long would that wort have to sit before it became oxidized?[/quote]
Hey Chris, no hostility from you and none directed toward you. Yes, I’m 100% certain my starter tasted oxidized. I tasted the wort prior to crashing it in the fridge, so I detected oxidation right off the stir plate. Unfortunately, I didn’t do a stringent blind triangle on the finished beer, so maybe I’m fooling myself, but I thought I could detect the same oxidized, stale taste in the beer (although to a much lesser extent) as I could in my starter. This was a 3 qt. starter for 5.5 gal. batch of my 1.073 70 IBU Rye IPA.[/quote]
I’ve noticed the same thing in my starters, Denny, definitely an oxidized taste (among other not so pleasant flavors).
Here’s the thing: as long as a starter is fermenting fast enough, it’ll create enough CO2 to displace all the oxygen and other gases in the starter flask (note I said displace, there really isn’t any positive pressure inside the container- not unless it’s corked solidly or has a full airlock on it). Once fermentation has slowed to a crawl or stopped, the CO2 in the flask will eventually dissipate and be replaced in large part with other gases (including oxygen). CO2 will tend to remain in the flask in higher concentration, being the heaviest gas, but it will eventually reach equilibrium with the outside air. If the flask is on a stir plate during this time, there is enough movement of the wort to keep the CO2 inside the flask agitated, thus accelerating the displacement of CO2 into the outside atmosphere. In my opinion, this is probably the point where the bulk of oxidation occurs in a stirred starter.