Beer is made in kettles and fermenters, not in computer models or spreadsheets. Just like weather is made in the atmosphere and not in the models that fail to predict it (my local forecast for yesterday was 12-18” snow, 12 hours before we got a little drizzling rain... stuff is complex, I’m not mad at em).
So what I'm hearing is: "supercomputer"
And finally, one factor that may muddy the science vs reality is the effect that pitch rate has on the length of the lag and log phases. Under pitching may simply lengthen these periods slightly, keeping the yeast in ester mode longer, thus resulting in more esters.
You also posted earlier about keeping yeast in log phase, but earlier referring to availability of O2:
Hmm... may want to revisit that hypothesis. Esters come from growth. The access to oxygen keeps a small pitch of yeast in the growth phase longer.
This gives me a bunch of questions that I didn't see the answers to in this thread or in Zymurgy:
Do you have a target pitch rate, or some proxy which approximates a target pitch rate (e.g., fresh vial in 1 qt starter at ~1.040)?
Do you add oxygen or air initially? Is there a target initial DO rate? Is there a nominal rate and then you count on availability of oxygen in headspace? Do you feel strongly about these things, or do you only feel strongly that it is the entire process that makes the difference (as seems to be what you're saying in the last post)?
I've been working on my hefe for years and I still fiddle with pitching rate and oxygen more than I fiddle with anything else, really. My experience has been: that's how I make wildly different beers from the same ingredients. I pitch low (~6E6/mL), and I do 90 seconds O2 at 1LPM. I used to do a mix-stir for O2 since some smart folks I respect pointed to low DO driving esters, but that hasn't worked for me.
Also, while I directed this a bit to hacksackr if anyone else has experience playing with any of these variables I'd love to hear about it.
I love this thread! I feel like a lot of dogma leaks into brewing which may help new folks climb the learning-curve faster initially, but I think it does a disservice to our shared community understanding. There's a lot of great brewing literature that amalgamates knowledge from thousands of years of trial and error. And there are so many paths to amazing beer that on paper don't seem like they'll ever work. The more I've tried those weird paths, the more I realize that I have no idea what's going to make a good beer, but I can try it and see if it works for me.
Great thread, thanks for still being passionate about this stuff folks <3
I guarantee I’m going to miss one or more of those questions, I’ll do my best though. And I don’t think I caught which yeast you were using 300/3068 is moderate in banana imo, unless you go up to like 13-14 Plato.
My basic hefe yeast review
300/3068: balanced banana clove
380/3333: big banana, moderate clove
351/3???: huge clove, minimal banana
My advice is to use the one more suited your desired profile and tweak from there; not try to get a yeast to do something it’s not the best at, if that makes sense. Or blend yeasts...
Yeast and oxygen: ok this is a bit of a black box. I aim for 7M/ml in around 4.5 gallons (2 quarts of wort reserved for speise)of wort. 120B cells-ish total. I don’t count yeast every time I brew, I’ve kinda fallen in the habit just using one tube (flex pouch or whatever) of WLP380 if it’s within one month of production I just pitch that which closer to 6M/ml. If the yeast is older (or summer shipped) I do a 1l starter and one pack which should be close to 7M/ml. I don’t oxygenate a hefe directly. I pitch the yeast into the fermenter and drop the wort in on top from the top of the fermenter. DO ends up around 7ppm generally. I feel like the pure O2 makes the yeast character muted for some reason. Probably the higher DO level worts produce less higher alcohols isoamyl in particular, just a guess though.
Maybe my opinion on yeast growth and ester production is somewhat simplistic, but yeast have to reach a critical mass of cells in the growth phase. So if you pitch that critical mass directly, then they’ll skip the growth phase, and start making alcohol. If you pitch a normal pitch rate they grow X amount of cells. If you underpitch the number of new cells needed is greater than X. Now higher DO levels seem (to me) to make them reproduce cleaner, probably as a result of increased sterols. Limited DO and an underpitch seems to produce a dirtier growth phase if you will. Like there’s yeast afterbirth laying all over the place. Now the open fermentation O2 thing is somewhat different. I’m not positive what the actual mechanism is. Someone suggested it’s due to the CO2 coming out of solution quicker. I just know that if I put an airlock on my hefe isoA seems noticeably lower than when I leave it open. That nih article big monk posted had test results showing higher levels of IsoA in semi-aerobic fermentation, but I don’t remember reading a definite cause for it. But to be clear I’m not counting on atmospheric O2 to dissolve into solution at all. Once the foam starts coming up there’s no O2 getting past it into solution, but the yeast in top are exposed to atmospheric oxygen at some level.
All that being said I don’t think isoA production is even that simple. I feel pretty strongly (without any non-anecdotal evidence) that there is more to it than just the intercellular pathway of yeast. I think it there is some creation after the active fermentation. That just comes from tasting the beer. When it’s finished I don’t smell or taste a bunch of banana, but usually taste sulfur, a week later less sulfur, some IsoA, two weeks later no sulfur lots of IsoA. Is that causality, absolutely not, but if you google IsoA synthesis, labs use sulfuric acid to catalyze the reaction from isoamyl acetate and acetic acid. Just a theory of mine, that I’d like to have disproven.