Fundamental shift in yeast starter preparation

cactusgarrett

I thought I'd spin this off of the yeast slurry discussion; don't want to take that over.
@renstyle mentioned listening to the Bru Lab episode 80 about yeast, which I just finished. It's got my mind reeling; not really sure what to think yet. In the episode, they reference an earlier episode (062) where work was done to show that yeast starters prepared at 1.008 gravity produced 500% more, healthy (quantity) yeast cells due to the yeast relying on respiration. The takeaway is you can use less extract to prepare the starter, and pitch far less than the online calculators suggest.
The reasoning seems logical, and I can usually be talked into considering anything with seemingly sound logic, but them referencing the work (from episode 62) that suggests a starter wort of 1.008 is best for growth (with enough nutrient/nitrogen)? It goes against ALL the online starter calculators to date, and I don't know what to think.
And the idea that when they asked themselves "how much nutrient/nitrogen do you use?", they started with 5g in 1-2L, then noted the Wyeast instruction is (for their product) 2.2g in 5gal - that comes out to 0.1g/1L, not 5g. Other resources note that if you use too much of these nutrient products, you can be doing harm by poisoning the yeast with too much nutrients such as Zinc.

day_trippr

Good luck, but you lost me at Bru Lab...
Cheers!

cactusgarrett

Right. I mentioned it in the other thread - I'm trying to temper any biases against the Brulosophy guys and their "hot takes" (mine and others) while digging into this. This work, though, was actually done by Maria Moutsoglou, who (at the time) worked for Sierra Nevada (at Molson Coors right now). I'd like to think that brings a bit more gravitas to the topic.

Bassman2003

This should be pretty easy to test. Just make two starters side by side, one with the lower gravity wort and see how much slurry you end up with.

cactusgarrett

The studies state, though, that despite better cell growth, the cells are better equipped to ferment from respiration (vs fermentation), and that you can pitch 500% fewer cells into standard wort. Seems like this would throw off the "count by volume/weight" aspect.

VikeMan

I havent listened to the podcast, but I suspect the amount of O2 and nutrients become critical.

Is it 500% more cells produced in the starter, or is it 500% less cells needed into the wort?

cactusgarrett

From memory, it was 46% more cells generated in the "starter" (lab material) and of those cells, 500% fewer were needed for a comparable fermentation of "standard" gravity wort/beer.

cactusgarrett

Mainly nitrogen.

cactusgarrett

I also want to be clear that I'm not trying to make this into be a Brulosophy bashing/bias session. I supposed to give this discourse a fair shake I should have omitted that they reported on it in the first place.

McMullan

Yeast are living organisms. Treat them as such and you will be rewarded for your respect of living things. If one wishes to select for the best possible yeast cells to ferment malted barley wort then - wait for it - culture them in malted barley wort. The flawed assumptions based on very limited data do not refute what we already know inside out. The inconvenient truth. Brulosophy seem to get so awesomely excited about all kinds of unconfirmed ****, in the name of advertising mainly. That's what Brulosophy is all about, right?

cactusgarrett

Again, this isn't Brulosophy's work, it was Maria Moutsoglou (at the time) at Sierra Nevada. Can we please curb the Brulosophy hate for an attempt at reasonable discourse here?

VikeMan

I just listened to episode 62, where Maria Moutsoglou actually talked. A couple of takeaways:
The ratio of Carbon to Nitrogen in the reduced gravity, nitrogen supplemented wort was 100 (vs 850 for the regular starter wort).
She did not say that you could pitch 500% less yeast into the main batch of wort. It was the host who said something about 500% in a rambling, frankly indecipherable statement. At the point where he said it, in some sort of a perceived epiphany, nothing that went before suggested that you could pitch 500% less yeast. And again, Maria Moutsoglou made no such claim.
Before I'd get too excited, a big thing that's missing here is tasting panel data.
And here, I believe, is the paper, which I have not read through yet:
https://onlinelibrary.wiley.com/doi/full/10.1002/jib.621
ETA: According to the abtract, the 46% increase in cell production was for the 2 Plato low C:N wort vs the 2 Plato high C:N wort. It was not in comparison to a "normal" gravity starter wort (in spite of what the podcast may have implied).

McMullan

'Haters' aside, reasonable discourse involves what here? Maria what's-her-face is entitled to her opinions, but has anyone with any credibility actually confirmed her opinions in a way considered convincing? I suspect such a grossly simplistic idea has been considered numerous times independently. Perhaps there's a reason we haven't accepted the idea already?

TheMadKing

And this about wraps it up for me. She's comparing which is the more limiting carbon or nitrogen, and it sounds like nitrogen. Which makes sense when you realize that most off the shelf yeast nutrients smell like ammonia. It sounds like she performed a perfectly valid test of the effectiveness of common yeast nutrients that was garbled by poor wording or misunderstanding by the host.
Thanks for clearing that up Vike!

VikeMan

To be fair though, she did also discuss respiration vs. fermentation, and the (true) fact that respiration is a lot more efficient way to make ATP (energy, which is needed for growth and propagation) than fermentation is. And a way to force respiration (and less fermentation) is to limit the carbon concentration and provide enough nitrogen.
That said, will a starter done that way result in better (tasting) beer?

cactusgarrett

Along the lines of Vike wrote. I'm looking for legit reasons other than gut reactions and "it's what we've always done before" to not consider it further.
My swiss cheese memory for data aside, the gist of what was being put forth is what I wanted to discuss here - making starters at 1.008. You're also putting forth good points that Maria Moutsoglou brought data, and the host is making extrapolations from it

DuncB

@cactusgarrett
This thread
is very good about yeast growth and explains how and why some of the experimental findings aren't that useful in the real world.

ft4pctuzusj.png

Optimizing Yeast Starters and Large-Scale Yeast Production - Sui Generis BrewingOptimizing yeast starters is important for the frugal brewer and for producing large batches of beer. But what can you achieve at at home?

jkiin302kba.png

suigenerisbrewing.com

Bramling-Cross

Thanks for that, Vikeman. I started and then deleted a couple different posts that opened with, "Five-hundred percent is an awfully big number. What sort of starter volume are they using? It must be close to a full batch size?"
I get it, now. Thank you.

cactusgarrett

Right. For those who haven't listened to the episode, that's the whole basis of the study and the concept the host is putting forth when suggesting starters can be made with less sugar.
And to be clear, I don't buy this all, either, but I wanted a good reason (aside from it not passing the sniff test) to not consider it further.

SanPancho

whatever happened to the ol' "OLIVE OIL IN YOUR STARTER" hubbub from a while back.....

CascadesBrewer

I have not listened. My impression (based on a tour of a local yeast lab) is that during fermentation there they continually feed the yeast sugars to keep the gravity levels lower than what kicks off the Crabtree effect. This translates into much more cell growth. Are they just making a starter in 1.008 wort, or are they continually keeping the wort at around the 1.008 gravity level?

cactusgarrett

Starter in 1.008 medium and making sure they hit a specific level of nitrogen in order to rely on respiration instead of fermentation. They didn't mention anything about feeding to maintain 1.008, so I'm assuming that didn't happen.

cactusgarrett

Great stuff; thanks.

McMullan

Is respiration more efficient for yeast cells? Really? It depends on the yeast and its environment. If we look beyond a simple comparison of how many mols ATP get produced from a mol of glucose, fermentation vs respiration; due to the ecology of brewer's yeast there are actually proteomic restrictions making respiration in high carbon environments far too costly, metabolically. But the logic that we therefore simply reduce the carbon/energy/gravity and increase nitrogen in starter wort, to increase growth therefore biomass, is expressing a form of biased tunnel vision. Being essential for growth, e.g., for nucleic acids and proteins, yes, nitrogen is required, but glucose/energy/ATP is required to the extent biomass production is positively correlated with wort gravity, not just nitrogen. We use relatively low gravity (<1.010) culture media in labs to propagate yeast, but these procedures are optimised to produce yeast cultures for non-brewery use. The aim isn't to maximise biomass. On the other hand, brewers follow procedures that maximise biomass so sufficient yeast cells for successful brewery fermentations get pitched. There is enough nitrogen and carbon in malted barley wort with an SG=1.040 to support sufficient growth in brewing environments. It works just fine. There's nothing broken here. Nothing to fix. We don't just want our brewer's yeast cells to grow, we want them adapted to ferment brewery worts. Let's just call it 'a gut reaction' and stop wasting valuable brewing time trying to be different for the sake of being different.