HI all, first time post for me. Brewed the BCS bpa, pitched with Wyeast 3522 1L starter@60F starter and aerated by rousing for a few minutes. I brewed this before holding temp at 68 and got excessive banana aroma, so this time I kept it at 62, where it held steady for the first day and a half. Got a lot of kruesen overnight and overpressured the carboy by clogging the airlock. Temp rose to 66 overnight ( beginning of 2nd day of fermentation). Now it's got a blowoff and a lot of kreusen is coming off, with a bit of a mess from the initial spooging that happen.

There was pressure buildup overnight, but the growth phase probably was near complete before this happened (there was a nice yeast top-layer yesterday evening), so it was probably during anaerobic that pressure built up, what does head pressure do to yeast during this phase of fermentation? I know it'll stress them some, but I think during growth it inhibits ester production (am I wrong on this) which mostly occurs during growth anyway. Basically, am I going to have another banana-bomb? What other things might've happened that are worth considering when analyzing the final beer?

That banana compound is iso-amyl acetate (I believe, IIRC). Temperature can play a big role in the production of it, but so can wort aeration levels and wort nutrients available. Underpitching can also lead to this as well. What was your OG for your bpa? As a 1qt starter even with fresh yeast will only go so far for a clean and healthy ferment.

[quote="wwyw"]initial spooging banana-bomb?]
Thats all I saw! Sounds dirty! mrmalty.com and a one inch blow off is probably your quick solution.

pressure during fermentation decreases ester production as well as higher alcohol production, allowing you to ferment a beer faster and warmer while not getting excessive esters and fusels. Many large lager brewers now do this to get a cleaner lager out faster than they could at lower temps. That being said, the amount of pressure from a clogged airlock probably had a minimal effect. If anything, the beer might be mildly less estery.

Don't sweat it. It'll be rock star. excessive head pressure during the growth phase can reduce ester production - but it doesn't sound like things got way outta control for ya. If you had a nice pitch, and started at that fermentation temp, you should be good.

BTW, any chance you did a step mash on that banana bomb? Or just single infusion?

I did a single infusion on that one hitting 148, no stepping, this time I mashed at 155. I know for clove aromas a 110F step is important for ferulic acid 4 vinyl guaiacol, is there a similar mash step for acetal-carboxylic acid? Since this necessary for yeast growth, it seems like the proper solution is sufficient aeration (which I probably didn't do last time, this time I aerated more) and lower ferment temps. been ramping up over the last two days from 63-66 to ensure the yeast finishes out completely.

Any recs on a good book on the ochem involved in brewing? I've read all the practical books but would love to get more into the science