Over the last few years, homebrewers have been made very aware of the importance of proper yeast pitch rates, which many ensure by making a starter a few days prior to brewing. While this certainly increases cell counts, it has little impact on the vitality of the yeast, a factor purported to be just as, if not more, important than viable cell count. In this xBmt, Ray Found compares a conventional yeast starter to a method designed to improve yeast vitality, results are in!
Interesting. Very interesting! Wonder how much difference it makes having the stir plate versus intermittent shaking a starter…
I wondered the same thing. Colin was pretty clear to recommend spinning it on a plate for 4 hours, hence our decision to do so. On our scale, though, I’d guess shaking every 20-30 min would probably work fine.
Love it. Just to clarify, was either batch hit with O2 prior to pitching the starters?
Nope!
Reading back through the comments it looks like Ray did indeed shake both carboys to aerate. Oh well, looks like a good opportunity to continue the experiment!
Fascinating. Any further explanation on this?
Not that I can provide, I’ll try to get more from Colin.
There’s a serious error in the interpretation of the Coor’s England experiment.
A batch grown starter never respires in the truest sense unless the glucose level is held below the Crabtree threshold of 0.3% glucose weight by volume. This phenomenon is due to something known as carbon catabolite repression (some researchers believe that is it due to respirative metabolic pathway saturation). Whether or not there was an appreciable amount of ethanol produced during the 4 hours that the culture was spinning is up for debate. However, all reproduction is fermentative in wort that has a glucose level that is above the Crabtree threshold. What happens is that O2 and a small amount of carbon are shunted to the respirative metabolic pathway for the production of ergosterol and unsaturated fatty acids (UFAs).
With that said, I have preached yeast vitality (i.e., health) over cell count for a while now. That’s why I preach pitching at high krausen over allowing a starter to ferment out. High krausen occurs when the cell count reaches maximum density for the medium into which it was pitched. Allowing a culture to proceed beyond this point results in reduced vigor upon pitching unless dissolved O2 is increased due to lower ergosterol and UFA reserves. Pitching at high krausen is a part of the perceived magic in my method. It reaps the rewards of batch propagation while only paying a partial price with respect to vigor. Initial O2 demands are lower because the ergosterol and UFA reserves are not as depleted as they would be if the fermentation was allowed to proceed to quiescence.
High jack - popular mechanics has an interview with Marshall that just posted today. Go read it.
Colin outlines the starter method here beginning around the 47:00 mark.
A link for the lazy…
What a cool experience!
Yeah, very cool Marshall. Nice work !
Thank you!
Wow! What a testament to all your hard work…
Congratulations on the article and thanks for sharing your results! I love it! Once you reach 100 exBEERiments, you should compile them all for a “tell-all” book. Seriously, I would buy it! I was telling my buddy the other day about your site and how they are the ideas in brewing that we all wonder about but never had the balls to test them out ourselves.
Well done and wicked cool!
As much as I commend Marshall for doing these experiments, don’t let it discourage you from doing your own! Don’t blindly believe him, me, or anyone else. Try things for yourself and discover your own reality!
Especially since the whole point of peer review in science is to increase confidence in (or refute) other research.
Spoken like a true hippie! ;D
Agreed on all accounts. There are so many variables in brewing that there is no guarantee that someone else’s experiment results will match your own. This is especially true when flavor is your primary endpoint, as in many of Marshall’s experiments.
My typical response to the brulosopher experiments are either “that makes sense based on my personal experience” or “I’ll have to try that for myself sometime”.
And congrats on the PM post, Marshall!