Fundamental shift in yeast starter preparation?

[VikeMan]

I will have a listen to the podcasts later in the week.

The paper might be more value than the podcast:
https://onlinelibrary.wiley.com/doi/full/10.1002/jib.621

I would skip the podcast(s) and go right to the paper. The podcasters claim some numbers and concepts not supported by the paper.

 

[onlyhere4science]

Maria Moutsoglou addresses the cost for inclusion of yeast extract for nitrogen vs. using full strength wort for prop media here. Sounds like because you're using less DME/wort sugars, it's more cost-effective to produce cells with low OG/high nitrogen vs. standard wort. So the cost comments here are kinda off imo.

Lest we forget that The Journal of the Institute of Brewing is peer-reviewed and David Quain is the editor. So there is fact checking done on the work itself.

 

[VikeMan]

Maria Moutsoglou addresses the cost for inclusion of yeast extract for nitrogen vs. using full strength wort for prop media here. Sounds like because you're using less DME/wort sugars, it's more cost-effective to produce cells with low OG/high nitrogen vs. standard wort. So the cost comments here are kinda off imo.

The paper we've been discussing, i.e. this one...

https://onlinelibrary.wiley.com/doi/full/10.1002/jib.621
...does support that low (2P) gravity starter worts (with adequate nitrogen) are more cost effective, i.e. produce more cells per unit weight of sugar, and I have no problem with that. The problem I see is that podcasters seem to have misinterpreted the data and led people to believe that a 2P starter of a certain volume will produce as many or more cells than an 8P (or 9P or 10P) starter of the same volume, which the data doesn't support.

 

[onlyhere4science]

The paper we've been discussing, i.e. this one...

https://onlinelibrary.wiley.com/doi/full/10.1002/jib.621
...does support that low (2P) gravity starter worts (with adequate nitrogen) are more cost effective, i.e. produce more cells per unit weight of sugar, and I have no problem with that. The problem I see is that podcasters seem to have misinterpreted the data and led people to believe that a 2P starter of a certain volume will produce as many or more cells than an 8P (or 9P or 10P) starter of the same volume, which the data doesn't support.

You're right - you don't make as many cells by volume with a lower P media at least with the conditions used in the paper. So yes...you make more physiologically shitty cells with high OG.

Just for data sake, actual numbers numbers from the paper are in the Supporting Info. If we compare H5 which is plain wort/no additional nitrogen (e.g., standard brewing prop media), peak cell counts were 42.1 x 10^7 cells/mL. Peak cell count for L1 (2P, high nitrogen) was 30.1 x10^7 cells/mL. Copied the table below for reference.

Table S7. Properties of S. cerevisiae growth profiles in YCM or wort with high (H) or low (L) C:N ratio. Significance established against YCM, where significance is designated by * p ≤ 0.05, ** p ≤ 0.005, and *** p ≤ 0.0005 (α = 0.05).

Media Identifier​	Number of Growth Profiles​	% Viability a​	pH b​	​	% Ethanol (v/v) b​	Total Cells Produced (x 107 cells/mL) c​
YCM​	3​	99.0 ± 0.1​	5.08 ± 0.05​	​	0.89 ± 0.02​	26.8 ± 2.3​
H1​	2​	99.1 ± 0.3​	3.30 ± 0.04***​	​	0.88 ± 0.05​	17.2 ± 2.3*​
H2​	2​	98.1 ± 0.4*​	3.35 ± 0.01***​	​	1.76 ± 0.06**​	27.3 ± 1.7​
H3​	2​	98.9 ± 0.7​	3.45 ± 0.03***​	​	2.80 ± 0.21**​	32.8 ± 3.2​
H4​	2​	98.3 ± 0.4​	3.56 ± 0.08***​	​	3.80 ± 0.03***​	47.0 ± 0.5**​
H5​	2​	98.7 ± 0.3​	3.71 ± 0.06***​	​	5.24 ± 0.08***​	42.1 ± 0.1**​
L1​	3​	98.6 ± 0.1*​	4.99 ± 0.02​	​	0.68 ± 0.06*​	30.1 ± 5.3​
L2​	2​	97.5 ± 3.2​	4.85 ± 0.09*​	​	1.89 ± 0.01***​	33.7 ± 4.5​
L3​	2​	97.6 ± 3.4​	4.63 ± 0.03**​	​	3.06 ± 0.00***​	31.5 ± 1.7*​
L4​	2​	98.7 ± 1.6​	4.69 ± 0.00**​	​	3.96 ± 0.05***​	36.9 ± 5.9​
L5​	2​	99.0 ± 0.6​	4.74 ± 0.05**​	​	5.03 ± 0.06***​	38.4 ± 0.9**​
aAverage and S.D. for yeast in stationary phase. bAverage and S.D. of pH obtained from samples collected for fermentation efficiency analysis (n = 2) at the completion of growth. cDifference between average of four stationary phase cell concentrations and initial cell concentration for each growth profile.

 

[McMullan]

Lest we forget that The Journal of the Institute of Brewing is peer-reviewed and David Quain is the editor. So there is fact checking done on the work itself.

Not really. Peer review is more about 'Is this research publishable?'. Fact checking is more about independent confirmation either by reviewing existing data in the literature, if there are any, repeating experiments and/or designing new experiments to challenge the hypothesis. Oddly, assuming we start with sufficient healthy yeast cells, 1.040 wort starters work just fine, regardless whether they're stirred, shaken or just left in a cupboard. My fermentations proceed at a respectable rate and attenuate to around 80% -/+ a couple points. I'm not sure what needs to be fixed, tbh. Perhaps the research - if confirmed - is of more interest to some large commercial breweries struggling to propagate sufficient yeast (within budget) due to scale. At home-brew scale the 1.040 starter has been confirmed over and over. Seems a bit odd, to me, to be diluting starter wort therefore available nitrogen then adding nitrogen. I don't expect to see any significant improvements for home brewers.

 

[onlyhere4science]

Not really. Peer review is more about 'Is this research publishable?'. Fact checking is more about independent confirmation either by reviewing existing data in the literature, if there are any, repeating experiments and/or designing new experiments to challenge the hypothesis. Oddly, assuming we start with sufficient healthy yeast cells, 1.040 wort starters work just fine, regardless whether they're stirred, shaken or just left in a cupboard. My fermentations proceed at a respectable rate and attenuate to around 80% -/+ a couple points. I'm not sure what needs to be fixed, tbh. Perhaps the research - if confirmed - is of more interest to some large commercial breweries struggling to propagate sufficient yeast (within budget) due to scale. At home-brew scale the 1.040 starter has been confirmed over and over. Seems a bit odd, to me, to be diluting starter wort therefore available nitrogen then adding nitrogen. I don't expect to see any significant improvements for home brewers.

If you do what you've always done, you'll get what you've always got. Seems like a common mindset in home brews and commercial brewers, which is fine. No one can argue there is anything wrong with respectable rates and respectable attenuations. On the other hand, there are those that may see the opportunity in innovation that leads them to discovery and success that fuels their home brewing passion.

The paper cites other peer-reviewed research that dips into Crabtree regulation of brewing yeast effect. It's not like the research re-invented the wheel, it simply applied a known theory in a practical way for brewers to employ. And it would be kickass to see more research that jumps off from the paper's starting point...kinda like what Brulosophy did. More peer-reviewed work would be even better. Healthy skepticism is key to the scientific pursuit, probably how this research came along in the first place.

I'm just happy people are talking about yeast tbh.

 

[sibelman]

The reduced-gravity starter idea is somewhat intriguing. The expression "500% less" is frankly hilarious.

Does the speaker perhaps mean "reduced to 1/5th of the original amount", which would be 80% less? If so, it's a very odd way to say it.

 

[VikeMan]

Does the speaker perhaps mean "reduced to 1/5th of the original amount", which would be 80% less? If so, it's a very odd way to say it.

I'd say It doesn't really matter, as that wasn't true anyway. I would be nice, but probably wishful thinking, if "everyone" would read and understand the paper. It would be a lot easier to discuss.

 

[Bassman2003]

I listened to the podcast in my car and it is quite interesting. The Dr. is well spoken and explains everything quite clearly in brewing terms. My only question is about the dilution/starter volume. She mentions taking 13P wort and diluting down to 2P but I can not find much information about volumes. Looking at the table above it seems everything was at the same volume so the 2P wort was very efficient in making cells for the amount of ingredients. But, at comparable volumes, it made fewer cells than the 13P wort. So that would lead me to think to beat the 13P wort in cell count, one would need to almost double the volume of the 2P wort. Is this correct?

While this might save larger breweries money but at our scale, making larger starters is not very practical. I make 2L starters with 1.040 wort. If I am going to employ this method it seems I would need to make 3-4L starters to actually make more cells. While the high Nitro starters create healthy cells, I do not see the aspect of under pitching appealing. I still want to create/pitch the correct number of cells. Please let me know if I am off base as scientific papers seem a bit overwhelming to me at times.

 

[onlyhere4science]

I listened to the podcast in my car and it is quite interesting. The Dr. is well spoken and explains everything quite clearly in brewing terms. My only question is about the dilution/starter volume. She mentions taking 13P wort and diluting down to 2P but I can not find much information about volumes. Looking at the table above it seems everything was at the same volume so the 2P wort was very efficient in making cells for the amount of ingredients. But, at comparable volumes, it made fewer cells than the 13P wort. So that would lead me to think to beat the 13P wort in cell count, one would need to almost double the volume of the 2P wort. Is this correct?

While this might save larger breweries money but at our scale, making larger starters is not very practical. I make 2L starters with 1.040 wort. If I am going to employ this method it seems I would need to make 3-4L starters to actually make more cells. While the high Nitro starters create healthy cells, I do not see the aspect of under pitching appealing. I still want to create/pitch the correct number of cells. Please let me know if I am off base as scientific papers seem a bit overwhelming to me at times.

A fair question for sure. Seems like there was still p good growth in the 2P recipe, but certainly lower than an 8P recipe from the example provided in the table above. I think the quote from the paper below is interesting but def applies more to commercial brewers:

The total cell count in low C:N wort with 2°P sugar was 301 ± 53 x 106 cells/mL (Table S7). For a standard wort (13°P) and a pitching rate of 6.5 x106 cells/mL, the target inoculum could be met with a 2% (v/v) transfer. This is markedly more efficient than the common brewery scale-up strategy that uses a 10% or more (v/v) transfer (14).

It seems like you might suggest there is a benefit to pitching a higher quantity of physiologically unhealthy/lower vitality cells vs. a lower concentration of physiologically vital cells. In this case, around 28% fewer cells would be pitched with a 2P recipe of "same volume." I would bet the tradeoff is not exactly linear, but this would be something to test for sure!

 

[Bassman2003]

Thanks for your reply. In my mind, the best case scenario is pitching a high quantity of physiologically vital cells. I also wonder about the middle ground. While the research shows higher sugar inhibits ATP production and makes the environment less conducive for growth, does just adding more nitrogen to a 13P wort show any benefits? What about higher nitrogen but 6P wort? etc...

 

[onlyhere4science]

Thanks for your reply. In my mind, the best case scenario is pitching a high quantity of physiologically vital cells. I also wonder about the middle ground. While the research shows higher sugar inhibits ATP production and makes the environment less conducive for growth, does just adding more nitrogen to a 13P wort show any benefits? What about higher nitrogen but 6P wort? etc...

Anytime dude. Agreed on your thoughts on best case scenario.

Paper shows results with a good range of OGs with and without nitrogen. It’s my understanding that adding nitrogen in the prop media regardless of OG had a benefit - last graph shows that attenuation was improved for all OG when nitrogen was added. Sounds like there is likely a middle ground or at least an opportunity to improve your yeast health w nitrogen/yeast extract while still meeting a pitch rate target.

 

[Bassman2003]

When I grow up yeast, I start with a frozen 50ml vial. Go to 250ml of wort then ~2L. I pressure can my wort so I make a single mason jar with double strength wort and dilute with water. So I am seeing some opportunity to increase the dilution a bit as well as increasing yeast nutrient. While my container is limited to ~3L, I could probably add some more water and a little less wort. This is with an assumption that the C:N ratio has a linear application from high to low.

 

[McMullan]

I skimmed over the paper (methods and results). I wasn't that impressed. Very limited data with a lot of variation. Probably even more if the experiments were done more than only twice. I'd expect triplicate experiments at least, in a design submitted for publication rather than a look-see. All research needs to be confirmed independently and this research is definitely no exception. What puzzles me, though, is the initial steps in brewery yeast propagation usually use about 2P agar/media with yeast extract and peptone. In my case, when starting from scratch using stored/frozen yeast, there's an initial overnight 10ml prep that gets streaked on agar plates for QC and selection of healthy looking colonies, which go in another 10ml prep for 48 hours before getting stepped up to 100ml for another 48h. Then it's time to step up using 500ml 13P/1.040 starter wort with yeast nutrients. Subsequent step-ups, usually 2.5L then a half batch (12L) beer to full batch, are repitchings, in my mind, at home-brew scale.

As the link between yeast quality and fermentation performance has been established(5, 6), propagation must yield viable, physiologically ‘tuned’ yeast for serial repitching or for single use fermentation.

The best way to 'tune' brewer's yeast - to condition them metabolically against the stresses of fermentation environments and be fit for repitching is to pitch them into brewery wort. This has been known for decades. The cells develop a metabolic 'memory' of the fermentation environment, which is what we want. Once through the initial (millilitres) propagation steps yeast are ready for 13P/1.040 wort, with more than enough biomass production to harvest and repitch for optimised fermentations. For home brewers and micro breweries there is little to be gained in getting bogged down with yeast propagation practices optimised for large-scale brewing operations.

But it wouldn't surprise me if at some point 'Proper Starter 2(P)' hits the home-brew market. Imagine for a moment, a place where cans of unfermented wort - weak or not - actually sell for more than cans of beer. A new definition of being hoodwinked?

 

[madscientist451]

I'll go out on a limb here and predict that at the homebrew level, if you made two starters, one with my lazy-ass no oxygen, no nutrient no stirplate, 10.040-ish wort, jug with an airlock method and the other starter with the complicated method discussed here, that you won't be able to tell the difference in the beer at the end.
Or did has someone already test it out? The x-beeriment linked above didn't do the step feeding but did start with a low gravity wort.

Edit: Since I'm also kind of a cheapscate, if I can use less DME in a starter and the beer comes out the same, why not do that?
Yeah, I'm really not saving much money, and there's no way I'm going to fuss with step feeding a yeast starter.

 

[VikeMan]

Thanks for your reply. In my mind, the best case scenario is pitching a high quantity of physiologically vital cells. I also wonder about the middle ground. While the research shows higher sugar inhibits ATP production and makes the environment less conducive for growth, does just adding more nitrogen to a 13P wort show any benefits? What about higher nitrogen but 6P wort? etc...

In the paper's data, there's a little bit of a middle ground. See Figure 2-B. Under the conditions tested, the efficiency per gram of sugar benefit for low C:N wort was highest at 2P, and broke even with high C:N wort at roughly 4.5P. Any higher, and the low C:N wort was actually less efficient than the high C:N wort.

The reason for the highest per gram of sugar efficiency at 2P was believed to be due to suppression of the Crabtree effect (and I'd bet a paycheck that it was). You can see the same phenomenon in the high C:N wort, but it's not as dramatic, with the relatively lower nitrogen content being the likely reason for the impact being less pronounced.

Maybe someone will test "large volume, low gravity" starters vs. "low volume, high gravity" starters (both with adequate nitrogen), with the relative volumes calibrated to produce the same number of cells. And then make beer from these starters, and taste test panel the beejezus out of them, because all of this isn't very useful if the beer doesn't improve, or at least maintain the same quality at a lower cost.

Also, a thing that gives me pause is that the paper touted lower residual sugars as a de facto benefit of beers made with the yeast from low C:N starters, even calling the beers made with the yeast from high C:N starters "under attenuated." To me, under attenuated means attenuated less than the brewer intended. We have many knobs in recipe and process to influence attenuation. If we have styles/recipes that have evolved to get certain levels of attenuation from traditionally produced yeast, why would attenuating the same beer further be assumed to be an improvement? Everything gets a little drier and we therefore love it?

 

[RM-MN]

Edit: Since I'm also kind of a cheapscate, if I can use less DME in a starter and the beer comes out the same, why not do that?

Gordon Strong has reported that the often makes lagers and just pitches a single smack pack. Being a 4 time Ninkasi winner, he should know what beer should taste like. How does he get by without making a starter? You can't get much cheaper on starters than not making one.

 

[McMullan]

why would attenuating the same beer further be assumed to be an improvement?

From a big/macro brewery's perspective? It translates into more ethanol therefore more beer. More product per run of the brewery. They can use various tricks to maintain consistency of the brewery's products. Like a lot of research focusing on commercial challenges, e.g., high gravity brewing, it's about increasing profits and not necessarily of much use being applied at the nano scales associated with home brewing. I'd guess most home brewers don't even bother to propagate yeast before pitching into FV wort.

 

[Bassman2003]

Thanks for the discussion. The split between home and pro is often around money/profit. I am more interested in the increased performance of the yeast compared to saving money or lower plato wort. I think the use of the term under attenuated was in the context of expected attenuation compared to actual. I think we all want yeast that kicks ass. We can adjust our process around any yeast behavior, but if we can get them to perform optimally, then all the better.

One could put all of this into 'ain't broke, don't fix it' category, but that is the exact reason the research was done - for the pro brewers. They want to push the cost savings so they are looking for ways to improve process.

I see the overall premise as valid - to build up very potent yeast cells to then handle the stressful environment of fermentation. Do you go to bed early, pre-hydrate and rest up before a big event or keep your routine the same? It is easy enough to add some more nutrient and dilute some wort so I might try this to some extent. But the real determinant for me is better attenuation/performance and flavor consistency not biomass imho.

 

[VikeMan]

I think the use of the term under attenuated was in the context of expected attenuation compared to actual.

Maybe. But then, what was the expectation, and what was it based on? It's would be kind of odd to get less attenuation than normal, using the standard process on which the expectation was based, and then call it out as a shortcoming of the process.

I think they called it "under attenuated" because it was less attenuated than the attenuation they got from the non-typical process.

 

[Bassman2003]

I agree, kind of nebulous. "Normal" would be normal (13P wort). Where this discussion makes sense to me is attenuation. Using the normal 13P methods, it seems good attenuation is tied to a numbers game. More yeast often results in better attenuation in a shorter time frame. Less of these cells results in decent attenuation in a longer time frame. This suggests the cells themselves might be on the tired or weak side while the 2P cells seem to be able to do the same job with fewer workers. Thus showing that the health of the 2P cells allows for better performance. Flavor is unknown as you stated. (This is assuming that the examples in the table shown above were pitched into a fermentation).

 

[McMullan]

I wouldn't read too much into the claims yeast propagated in 2P wort express improved vitality compared with yeast propagated in higher gravity starter worts. It wouldn't surprise me, because even relatively low ethanol levels represent a significant stress factor in the fermentation environment. But it is more likely a very short-term effect that disappears and seems to overlook relatively high vitality of repitched freshly harvested yeast cells. - why serial repitching is practiced post propagation.

 

[Bassman2003]

Good points. I think this space needs some more experimentation to solidify any benefits. There could be some there there but results in finished beers would be needed.

 

[IslandLizard]

Gordon Strong has reported that the often makes lagers and just pitches a single smack pack. Being a 4 time Ninkasi winner, he should know what beer should taste like. How does he get by without making a starter? You can't get much cheaper on starters than not making one.

Age and origin of that smack pack has much to do with the vitality and live cell count. I don't want to discredit Gordon Strong, but he may not obtain his yeast in places and at times, most homebrewers typically buy theirs: on a whim at their local store, or online, the yeast being 2-4 months old, on average, with an unknown history.

We don't know Gordon's batch size either... Maybe he brews 2 or 3 gallon batches. One fresh smack pack should work splendidly.

Also, a 1.040-1.045 OG Lager is similar to most starter gravity. With good wort oxygenation and pitching a fresh, highly vital pack, it may work very well.
One such pack in a Doppelbock would likely have a whole different outcome.

[Gordon Strong...] How does he get by without making a starter?

Maybe you can ask him?
Then report back to us how and under what conditions it works for him.

 

[CascadesBrewer]

I think they called it "under attenuated" because it was less attenuated than the attenuation they got from the non-typical process.

In the study they got the best attenuation from pitching harvested yeast, the worst attenuation from yeast built up with the normal propagation wort, and the attenuation of the yeast propagated in the low gravity/high nitrogen wort was in the middle. So they were using the repitched yeast as the base line to judge "underattenuation." I am not sure I recall seeing any other yeast performance metrics in the study (like lag time, or time to FG).

 

[CascadesBrewer]

We don't know Gordon's batch size either... Maybe he brews 2 or 3 gallon batches. One fresh smack pack should work splendidly.

I am not sure what Gordon has said in other venues. From his book "Brewing Better Beer" he says:

"There are two main ways I use yeast. Either I'm working with fresh yeast, or I'm reusing yeast from an existing batch. If I'm going to pitch new yeast, I will almost always make a starter to get the fermentation starting quickly." (page 130) There is some more info on his process for making a starter (1L with 85 grams of DME and yeast nutrient), and his process for working with harvested yeast.

 

[CascadesBrewer]

One open question I have about the low gravity starters is about the type and amount of "yeast extract" used. The extract used by the paper is "yeast extract 19512, OrganoTechnie S.A.S., France" which I have not seen listed for sale. Info: Yeast Extract - Organotechnie, fermentation and diagnostic peptones

The paper lists using 16g of yeast nutrient per L for the low gravity starter (plus some zinc). Depending on the purchase price, 16g per L of Fermaid-O or Fermaid-K would add about $1.50 to $4.00 to a 2L starter, negating any cost savings in DME. If instead a mix of say 1g/L of a yeast nutrient + 5g/L of DAP could be used, that would be around $0.80 for a 2L starter.

 

[McMullan]

I don't think 'lab grade' yeast extract from different suppliers is variable enough to matter, tbh. I've used several brands without noticing any difference. They all stink as bad as each other. But it is very expensive to use at the suggested rates beyond millilitre volumes. Cervomyces, in bulk, might actually be more viable, economically I don't think yeast extract is equivalent to fermentation 'aids' either. Yeast extract is so much more than a N source, which exposes another issue with the research, I'd say.

 

[onlyhere4science]

In the study they got the best attenuation from pitching harvested yeast, the worst attenuation from yeast built up with the normal propagation wort, and the attenuation of the yeast propagated in the low gravity/high nitrogen wort was in the middle. So they were using the repitched yeast as the base line to judge "underattenuation." I am not sure I recall seeing any other yeast performance metrics in the study (like lag time, or time to FG).

Need to remember statistics here... The paper shows no statistically significant difference in attenuation between harvested yeast and yeast propagated in ANY wort gravity that included nitrogen to achieve a C:N at 100. Harvested yeast did not perform statistically better, with the exception compared to yeast propagated in low nitrogen wort, and this difference increased as OG increased.

In the study they got the best attenuation from pitching harvested yeast, the worst attenuation from yeast built up with the normal propagation wort, and the attenuation of the yeast propagated in the low gravity/high nitrogen wort was in the middle. So they were using the repitched yeast as the base line to judge "underattenuation." I am not sure I recall seeing any other yeast performance metrics in the study (like lag time, or time to FG).

Lag time for propagation and time to reach end of fermentation were all reported in the paper... See Figures 2 and 3. Fermentation time increased for yeast pitched in high OG wort. Lag time increased linearly w/respect to OG for yeast pitched in low nitrogen wort.

I wouldn't read too much into the claims yeast propagated in 2P wort express improved vitality compared with yeast propagated in higher gravity starter worts. It wouldn't surprise me, because even relatively low ethanol levels represent a significant stress factor in the fermentation environment. But it is more likely a very short-term effect that disappears and seems to overlook relatively high vitality of repitched freshly harvested yeast cells. - why serial repitching is practiced post propagation.

As a home brewer if you only get one shot to make a beer, seems like you'd want that first beer with propagated yeast that perform optimally. Even pro brewers sometimes only get one tank to ferment and then sell, with no shot to blend with tanks that have harvested yeast. ¯\_(ツ)_/¯¯\_(ツ)_/¯

I agree, kind of nebulous. "Normal" would be normal (13P wort). Where this discussion makes sense to me is attenuation. Using the normal 13P methods, it seems good attenuation is tied to a numbers game. More yeast often results in better attenuation in a shorter time frame. Less of these cells results in decent attenuation in a longer time frame. This suggests the cells themselves might be on the tired or weak side while the 2P cells seem to be able to do the same job with fewer workers. Thus showing that the health of the 2P cells allows for better performance. Flavor is unknown as you stated. (This is assuming that the examples in the table shown above were pitched into a fermentation).

Seems like there is some confusion here. The paper reports that the same number of cells were pitched in the fermenters. Pitch rate in the fermenters was the same. The variable of pitch rate is eliminated. This is outlined in the methods section. They even eliminated the variable of dilution from the prop pitch to ensure volume and pitch rate were the same for all fermentations...

Brewery wort (370 mL) was added to sterilised 450 mL jars. Dissolved oxygen in the wort was 6 mg/L, determined using a HQ30D portable dissolved oxygen meter with a field luminescent DO sensor (Hach, Loveland, CO, USA). The pitching rate was 0.5x106 cells/mL/OG°P. Yeast cultured in YCM were included as a control in separate fermentations with yeast cultivated in high or low C:N media. Yeast were cultured in duplicate as described above into 25 mL of media until late log phase, and the viable cell concentration for each culture was determined. The volume of cells needed to meet the target pitching rate were centrifuged at 3,000 x g for 5 minutes at 22°C. The yeast pellet was reconstituted in 30 mL of wort and pitched into fermenters for a total wort volume of 400 mL.

 

[onlyhere4science]

I don't think 'lab grade' yeast extract from different suppliers is variable enough to matter, tbh. I've used several brands without noticing any difference. They all stink as bad as each other. But it is very expensive to use at the suggested rates beyond millilitre volumes. Cervomyces, in bulk, might actually be more viable, economically I don't think yeast extract is equivalent to fermentation 'aids' either. Yeast extract is so much more than a N source, which exposes another issue with the research, I'd say.

They do kinda mention this. I def think components of yeast extract that were non-nitrogen likely contributed positively. Def something future research could build on. While they say they interpreted results based on nitrogen (as that's what the recipes were based on), anyone could replicate the recipes and see what other factors besides metals were different and therefore potentially contributing. They could then go on to modify those non-nitrogen comments to see how performance is affected.

While the added nutrients and metal ions from yeast extract could have some impact on performance compared to standard wort, the interpretation of results in this study is focused on the differences in available sugar and nitrogen.

Future research can build on these results by investigating why yeast cultivated in standard wort with a high C:N ratio leads to sluggish and stuck fermentations. If wort was supplemented with FAN in the subsequent fermentation, could yeast overcome the deficiencies generated during propagation? Additionally, the scalability of this propagation protocol should be assessed to determine the impact on large scale fermentation performance. Finally, questions remain on the impact on the organoleptic quality of beer produced with yeast propagated under different conditions.

 

[CascadesBrewer]

Need to remember statistics here... The paper shows no statistically significant difference in attenuation between harvested yeast and yeast propagated in ANY wort gravity that included nitrogen to achieve a C:N at 100. Harvested yeast did not perform statistically better, with the exception compared to yeast propagated in low nitrogen wort, and this difference increased as OG increased.

Thanks for the clarification...I need to take a closer run through of the article text and not just look at the graphs.

 

[McMullan]

Need to remember statistics here... The paper shows no statistically significant difference in attenuation between harvested yeast and yeast propagated in ANY wort gravity that included nitrogen to achieve a C:N at 100. Harvested yeast did not perform statistically better, with the exception compared to yeast propagated in low nitrogen wort, and this difference increased as OG increased.


Lag time for propagation and time to reach end of fermentation were all reported in the paper... See Figures 2 and 3. Fermentation time increased for yeast pitched in high OG wort. Lag time increased linearly w/respect to OG for yeast pitched in low nitrogen wort.


As a home brewer if you only get one shot to make a beer, seems like you'd want that first beer with propagated yeast that perform optimally. Even pro brewers sometimes only get one tank to ferment and then sell, with no shot to blend with tanks that have harvested yeast. ¯\_(ツ)_/¯¯\_(ツ)_/¯


Seems like there is some confusion here. The paper reports that the same number of cells were pitched in the fermenters. Pitch rate in the fermenters was the same. The variable of pitch rate is eliminated. This is outlined in the methods section. They even eliminated the variable of dilution from the prop pitch to ensure volume and pitch rate were the same for all fermentations...

Brewery wort (370 mL) was added to sterilised 450 mL jars. Dissolved oxygen in the wort was 6 mg/L, determined using a HQ30D portable dissolved oxygen meter with a field luminescent DO sensor (Hach, Loveland, CO, USA). The pitching rate was 0.5x106 cells/mL/OG°P. Yeast cultured in YCM were included as a control in separate fermentations with yeast cultivated in high or low C:N media. Yeast were cultured in duplicate as described above into 25 mL of media until late log phase, and the viable cell concentration for each culture was determined. The volume of cells needed to meet the target pitching rate were centrifuged at 3,000 x g for 5 minutes at 22°C. The yeast pellet was reconstituted in 30 mL of wort and pitched into fermenters for a total wort volume of 400 mL.

Indeed, as I typed above, the data are very limited. But I'm wondering why anyone would express any willingness to accept the authors' conclusions - opinions, strictly - regardless The hypothesis really isn't that difficult to test. The research was published over 2 years ago. The lack of confirmation is deafening, and usually means the research findings weren't as valid as assumed, in terms of the authors' suggested benefits. I could be wrong, there might be a flurry of better designed experiments published at some point, to confirm the authors' research, but, until then, I'm content doing what I do to make yeast starters. Mainly because it seems to work very well, for some reason.

 

[mashpaddled]

Both the podcast and the brulosophy experiment are brutally wrong. I have no idea why anybody pays attention to them and the twenty vagrants in their garage.

Start with the premise that yeast given the most healthy and complete diet and compare them to yeast given a diet primarily of sugar, the yeast with the healthy and complete diet reproduce more favorably. If you start from an obvious place, you end up at the same conclusion as the paper.

The purpose of that kind of research is to help large breweries (and distilleries) produce repeatable beers on a repeatable timetable. Under those objectives, you want healthy yeast to perform efficiently and fully attenuate every time. You don't want sluggish or incomplete fermentations leading to production delays and batch variations. As a homebrewer, a few extra days in the tank for a few extra gravity points may not be a big deal. She's exploring whether a cost efficient balance to lab conditions (using expensive growth media) versus the usual starter technique exists and if so, whether it produces a better result. There are some attempts in the thread to extract entirely different points from her research.

 

[onlyhere4science]

Indeed, as I typed above, the data are very limited. But I'm wondering why anyone would express any willingness to accept the authors' conclusions - opinions, strictly - regardless The hypothesis really isn't that difficult to test. The research was published over 2 years ago. The lack of confirmation is deafening, and usually means the research findings weren't as valid as assumed, in terms of the authors' suggested benefits. I could be wrong, there might be a flurry of better designed experiments published at some point, to confirm the authors' research, but, until then, I'm content doing what I do to make yeast starters. Mainly because it seems to work very well, for some reason.

"I could be wrong" nah ur definitely right - it's totes crazy there hasn't been another literature article published yet on this very specific topic which all labs and all brewers are paying close extremely close attention to. I assume you read the journal article immediately when it came out like apparently the rest of the world's scientists so you could hop on the train to proving or disproving? I mean considering it takes 6 mo - 1 yr to publish in a peer-reviewed journal, the research itself by these would-be labs wouldn't take any time at all...surely not! These things are so easy to test as u say! Resources are most definitely unlimited and freely distributed by these labs, especially during COVID!!

Deafening indeed. Thank you for reminding us how the science cycle works. <3

I say this as a quality tech in a small brewery with very little resources who would love to test this out, kinda why I came here to see if any home brewers were taking it on after I heard the podcast. But idk, what do I know. ¯\_(ツ)_/¯

 

[Bassman2003]

Seems like there is some confusion here. The paper reports that the same number of cells were pitched in the fermenters. Pitch rate in the fermenters was the same. The variable of pitch rate is eliminated. This is outlined in the methods section. They even eliminated the variable of dilution from the prop pitch to ensure volume and pitch rate were the same for all fermentations...

Brewery wort (370 mL) was added to sterilised 450 mL jars. Dissolved oxygen in the wort was 6 mg/L, determined using a HQ30D portable dissolved oxygen meter with a field luminescent DO sensor (Hach, Loveland, CO, USA). The pitching rate was 0.5x106 cells/mL/OG°P. Yeast cultured in YCM were included as a control in separate fermentations with yeast cultivated in high or low C:N media. Yeast were cultured in duplicate as described above into 25 mL of media until late log phase, and the viable cell concentration for each culture was determined. The volume of cells needed to meet the target pitching rate were centrifuged at 3,000 x g for 5 minutes at 22°C. The yeast pellet was reconstituted in 30 mL of wort and pitched into fermenters for a total wort volume of 400 mL.

Thanks. I am confused a little on the volumes of the starters as they would need to be different if the final pitches were all the same cell count. But, this should hopefully clear away the idea that underpitching is somewhat part of the experiment.

 

[onlyhere4science]

Thanks. I am confused a little on the volumes of the starters as they would need to be different if the final pitches were all the same cell count. But, this should hopefully clear away the idea that underpitching is somewhat part of the experiment.

NP! The volume of the props produced more cells/mL than needed to meet the pitch rate target of the fermenters/jars.

From my understanding of the methods section, they withdrew the volume of cells from each prop required to hit the fermenter pitch target, spun the cells down to get rid of the prop liquid, reconstituted the pellet in the wort they would be fermenting in, and added that to the ferm. So all the ferms started with the same total volume and the same total amount of cells / mL.

 

[McMullan]

"I could be wrong" nah ur definitely right - it's totes crazy there hasn't been another literature article published yet on this very specific topic which all labs and all brewers are paying close extremely close attention to. I assume you read the journal article immediately when it came out like apparently the rest of the world's scientists so you could hop on the train to proving or disproving? I mean considering it takes 6 mo - 1 yr to publish in a peer-reviewed journal, the research itself by these would-be labs wouldn't take any time at all...surely not! These things are so easy to test as u say! Resources are most definitely unlimited and freely distributed by these labs, especially during COVID!!

Deafening indeed. Thank you for reminding us how the science cycle works. <3

I say this as a quality tech in a small brewery with very little resources who would love to test this out, kinda why I came here to see if any home brewers were taking it on after I heard the podcast. But idk, what do I know. ¯\_(ツ)_/¯

You'll need some wort, yeast extract, yeast, microscope and a hydrometer to monitor fermentation performance.

 

[onlyhere4science]

You'll need some wort, yeast nutrient, yeast, microscope and a hydrometer to monitor fermentation performance.

That’s not going to get a paper published, but sure…

 

[McMullan]

That’s not going to get a paper published, but sure…

It's pretty much what was done by the authors of the paper being discussed here. Why do you need to publish a paper about it? Aren't you more interested in testing the hypothesis for yourself, in your own brewery environment? Is there a business case to justify it?

 

[onlyhere4science]

It's pretty much what was done by the authors of the paper being discussed here. Why do you need to publish a paper about it? Aren't you more interested in testing the hypothesis for yourself, in your own brewery environment? Is there a business case to justify it?

I was really just here to see if others had tested it… but of course I’d be happy to sit down and answer these personal questions that pertain to my own career situation and curiosity in extensive detail for you to ruminate on and apply to the broader discussion we were having on why there isn’t a huge amount of other publications that built on this work. I’ll get right on it.