Do you aerate?

[Sadfield]

Tracy Aquillas wrote...

It is well-documented that yeast uses oxygen whenever it is available, even during fermentation, and yeast cells rapidly absorb essentially all of the oxygen made available to them. Yeast, however, will use the overwhelming majority (if not all) of the available oxygen in biosynthetic reactions, not for respiration.*

I think that pretty much confirms @Agentgonzo point. It'll use oxygen in both situations.

 

[foxy]

Tracy Aquillas wrote...



I think that pretty much confirms @Agentgonzo point. It'll use oxygen in both situations.

I should emphasize that although yeast is capable of performing respiration, this pathway is irrelevant for brewers because respiration does not normally occur in the production of beer. Tracy Aquilla

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[Agentgonzo]

We're not talking about respiration here (well, you are - no-one else is). Sterol biosynthesis (and the associated oxygen uptake) is a different thing entirely.

 

[foxy]

We're not talking about respiration here (well, your are - no-one else is). Sterol biosynthesis (and the associated oxygen uptake) is a different thing entirely.

Look at your original question.
So if you repitch yeast from the end of fermentation into fresh wort, you need to aerate the wort because the yeast needs oxygen to build up reserves and multiply.
But if you have exactly the same yeast and feed it sugar to condition the beer, it won't take up any oxygen at all?

The conversation is about brewers yeast a question which was answered. The yeast will multiply during the aerobic stage faced with a sweet wort, there can still be oxygen in the wort when yeast switch to anaerobic fermentation. as the sugars deplete cells die off, leaving a small number of cells which are still viable at the bottom of the fermenter.
This yeast can be reclaimed but the cell count needs to vastly increase to tackle another fermentation, hence why we make a starter. Oxygen can be tricky to give to yeast which are respiring (its toxic at high doses) Now put on a stir plate to give the yeast enough oxygen to multiply to the cell count required to tackle the wort. Pitch the yeast into the fermenter which has been aerated if the yeast decides it needs more cells it can still multiply but there comes a stage where the yeast switch to anaerobic fermentation and start making ethanol, the cycle carries on with cells dying and flocculating out of suspension. So from the billions of cells at the start they have depleted to a few million/billion .
Carbonate the wort to bottle those yeast still with us will consume the sugar without having to go back to aerobic respiration so any oxygen in the bottle is not taken up by the yeast. The oxygen stays there same in kegs. This is the biggest problem for commercials but not such a problem for home brewers who store there beer in a cool dark place and they sit there undisturbed waiting to be consumed.
I don't see anything which is hard to understand about that

 

[Chippy_Tea]

We're not talking about respiration here (well, you are - no-one else is). Sterol biosynthesis (and the associated oxygen uptake) is a different thing entirely.

 

[MashBag]

Has anyone got a link to the article please. Tried & failed.

 

[Sadfield]

Has anyone got a link to the article please. Tried & failed.

This one?

https://www.morebeer.com/articles/how_yeast_use_oxygen

 

[MashBag]

Thanks... Just off for a read

 

[foxy]

Not sure if this can be shared its from my digital account with BYO
https://byo.com/article/a-fresh-loo...-65252053&mc_cid=6598f9ae69&mc_eid=2e44d9045c

 

[MashBag]

Not sure if this can be shared its from my digital account with BYO
https://byo.com/article/a-fresh-loo...-65252053&mc_cid=6598f9ae69&mc_eid=2e44d9045c

Nah. Wants me to login.
Will probably work next month. Shame sounds like a good read.

 

[foxy]

Nah. Wants me to login.
Will probably work next month. Shame sounds like a good read.

I was thinking as much, members only, thought it was worth a punt.

 

[MashBag]

Wassit say then?

 

[foxy]

Wassit say then?

Have to split it up, Too big an article to paste in one go.

Part1

When we hear about ‘drying,’ we immediately try to understand this concept extrapolating from the other organisms, including multicellular ones,” says Jan-Phillippe Barbeau, Regional Sales Manager – Canada for Fermentis, one of the world’s leading suppliers of dry yeast. “People know it is impossible to dry entire mammals and keep them alive. However, we dry yeasts, which are single-cell organisms.”
There is no getting around the fact that adjectives often used to describe ideal yeast include words like “live” and “fresh,” and it sometimes takes additional explanation for people to wrap their heads around the idea that yeast can go through the drying process and still be both of these things. The fact is, dry yeast is not dead, but instead it is simply in a dormant state.
Making matters worse for the marketing departments at major dry yeast companies is the reputation dry brewing yeast rightfully earned over 30 years ago, which homebrewers of a certain age will still remember bitterly.
Proponents of dry yeast insist not only are these ways of thinking false in the modern brewing world we find ourselves in, but dry yeast comes with significant advantages vs. liquid yeast because it is more convenient to use and store.
So let’s take a look at dry yeast, how far it has come, and why homebrewers who stick with liquid yeast may want to keep it in mind for future brew days.

What Has Changed​

When homebrewing was just an emerging hobby, beer kits often included a packet of dry yeast. “The only dry yeast used to be baking yeast, which tends to have higher levels of bacteria and wild yeast, so this yeast became associated with mediocre homebrew,” says Eric Abbott, Technical Support Manager of Lallemand Brewing, makers of innovative dry brewing yeast. “Also, there used to be little variety of dry yeast strains, so all beers made with dry yeast tended to taste a bit the same,” he says.
Because baking yeast is designed to make bubbles (for airy bread), not alcohol or flavor, purity and testing was not as strict as they are today. So original dry yeast was substandard for homebrewers (and, as a result, liquid yeast companies Wyeast and White Labs were created and filled a giant hole for brewers).
Because the industrial process for drying yeast has improved, and following the growth of craft beer generally, there is more demand for dry yeast in commercial brewing. “Once commercial brewers realized the strains were improving and it was more cost-effective to ship and store dry yeast than the liquid yeast they had used, many started using dry yeast,” says Aaron Hyde, Portfolio & Strategy Manager for Bevie, a homebrew supply wholesaler and distributor of products including Mangrove Jack’s line of dry brewing yeasts. The process of making dry yeast requires it to be made in large quantities — we’re talking at least a couple of tons at a time — so widespread commercial adoption of dry yeast was necessary for homebrewers to have access to new strains.

How Dry Yeast is Made​

Like all yeast labs, dry yeast manufacturers start with a frozen culture. After purity tests, the yeast is propagated in a medium usually made of molasses and nutrients. Propagation occurs through multiple steps in containers of various sizes, from glass laboratory flasks to large, stainless steel propagation vessels.
While a brewery wants yeast to make alcohol, the lab wants yeast to make more yeast. This requires the careful addition of nutrients throughout the process. Certain nutrients promote yeast budding and increase in biomass. When the desired amount of biomass is achieved, the nutrients will be changed so that the yeast will produce glycerol, trehalose, and glycogen, which are compounds that strengthen the yeast cells, protect them from the drying process, and ensure they are healthy when pitched.
The yeast slurry is centrifuged, which produces cream yeast. To this point, the production of dry yeast is the same as the production of liquid yeast. But the cream is then dried through a combination of proprietary filtration, extrusion, and drying steps. The drying process is where the technological secrets are and yeast labs are generally tight-lipped about the specifics. To produce the best, healthiest yeast, labs use different drying processes.

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[foxy]

Part 2

Internationally recognized homebrewing personality and contributor to Brew Your Own, Denny Conn, is a proponent of dry yeast. “I look at the yeast characteristics I want for the beer I’m brewing,” says Conn. “If a dry yeast is available that will do what I want, it will be my first choice.” Conn notes that dry lager yeast strains are “exceptionally good” but he does not like dry Belgian strains.

“I think that there is always going to be a bit of a difference (between a dry yeast strain and a liquid yeast of the same strain),” says Conn. “But it is no more of a difference than you would find between the same strain supplied by two liquid yeast labs.” So, Conn advises brewers to default to dry yeast and only use liquid yeast when unsatisfied with the results.

The reason Conn prefers dry yeast is simple: “It is so much easier to use,” he says.

“Homebrewers often have it drilled into their head that they need to make a starter, count cells, and all sorts of nonsense,” says Conn. “Restrain yourself. Just sprinkle the dry yeast over your wort. That’s it.”

Dry yeast is packaged when it is rich in sterols and unsaturated fatty acids that will be wasted if dry yeast is rehydrated or a starter is made. Conn advises homebrewers just to add more dry yeast if brewing a high-gravity beer; he never makes a starter from dry yeast and no dry yeast manufacturer recommends rehydrating brewer’s yeast. That said, many homebrewers who have been rehydrating their dried yeast for years are stubborn in their ways, so companies do still offer the best practice advice for those who insist on rehydration. The fact is, rehydration generally won’t have any significant impact one way or the other, as long as it is done correctly (vs. negative impacts if not).

Microscopes and cell counting are unnecessary. Because the yeast cells are dried and therefore stable, there is no risk of mutation or degradation. And because dried brewing yeast has a minimum cell count and viability provided by the manufacturer, so long as it is used before its expiration date, pitching should be based on weight of dry yeast, not on cell counts. Pitch rate calculators often assume liquid yeast and using those calculations will result in significant overpitching of dry yeast. “Dry yeast is different from liquid yeast in some fundamental ways,” says Abbott. “It is rich in protein, sterols, unsaturated fatty acids, and internal sugar reserves,” so the amount of yeast needed will be different from liquid yeast. Even evaluating rehydrated dry yeast under a microscope is difficult since the increased permeability of the cell wall will make some live yeast appear dead, resulting in under-counting live cells. Brewers should be sure to use a pitching calculator made for dry yeast, which should give a result based on weight. In fact, Lallemand has an online pitch calculator that is not only designed for dry yeast, but is also strain dependent.

If homebrewers wish to add yeast nutrients, Conn suggests adding them during the last ten minutes of the boil. “I don’t know how much it helps,” he says. “But its easy insurance.” Conn also rarely oxygenates his wort when fermenting with dry yeast. “The purpose of adding oxygen is the yeast uses it to synthesize sterols. But dry yeast already has the sterols,” he says.

If all of this sounds too easy, that is precisely the point. Conn refers to himself as a lazy homebrewer and that is why he likes dry yeast. Conn does not crop and reuse dry yeast (though there is no reason not to) and he always uses entire packets of yeast.

But for homebrewers who want to save some money and do not need an entire packet of dry yeast, the remainder can be stored cool after removing oxygen.

Similar to liquid yeast, dry yeast should be refrigerated when stored, as all yeast will show a decrease in viability in ambient temperature over time. Yet, the need to keep dry yeast from getting up to room temperature for some period of time is much less critical than with liquid strains. This greater tolerance to temperature fluctuations often makes dry yeast of superior quality. Even if a homebrew shop unpacks new shipments of liquid yeast and puts them in the fridge as soon as they are received, there is no telling what temperatures the yeast was exposed to during transit. And this is the same for yeast ordered online, often being moved from truck to truck on a long journey to your front door. These temperatures almost certainly are outside the recommended range and the impact it may have is much higher with liquid yeast than a similar strain of dry yeast.

These considerations are likely a factor in traditional liquid yeast manufacturers dipping their toes into dry yeast creation. Recently White Labs released their most popular strain WLP001 (California Ale) as a dry yeast option, and announced more strains will be coming in dry format soon. Omega Yeast offers the kveik strain Lutra as a dry option, and Escarpment Labs now has House Ale as a dry yeast too.

“Homebrewers often want to emulate their commercial brewing heroes,” says Conn. “And if dry yeast is good enough for commercial brewers, it is good enough for homebrewers.”

There’s Even Dry Bacteria​

The popularity of kettle sours has exploded in recent years. For homebrewers wanting to try their hand at making them, three species of Lactobacillus are available for brewers in dry format.

L. plantarum and L. brevis are the most commonly used strains in quick- souring beer. Fermentis SafSour LP 652 and Lallemand’s WildBrew Sour Pitch are pure pitches of L. plantarum while Fermentis SafSour LB 1 is a pure pitch of L. brevis. Lallemand also markets a strain of L. helveticus under the name WildBrew Helveticus Pitch.

L. plantarum is homofermentative, meaning it produces only lactic acid. L. brevis is heterofermentative, meaning it produces multiple compounds — in this case, lactic acid, acetic acid, and some ethanol — depending on the amount of oxygen available to the bacteria. Lallemand reports that its strain of L. helveticus produces lactic acid to 3.2 pH in less than 24 hours, but can produce acidity with more complexity if left for 48 hours.

Whichever strain brewers choose (and many commercial brewers and yeast labs recommend using a blend of strains to get more complex acidity), dry bacteria strains are more convenient to use and are made to work in wort, so they will produce consistent, predictable results for brewers. Other sources of bacteria might not be pure strains and if they are mixed cultures, these cultures change over time.

 

[foxy]

Part 3

The Future​

As extruding and dry techniques have improved, there is now a plethora of brewing yeast strains available in dry format. In addition to a number of traditional ale and lager strains, kveik strains are now available in dry format. Fermentis even makes SafBrew LA-01 for fermenting low- and non-alcoholic beers, though not yet in homebrewing-size packets.
The manufacturing of dry yeast is so advanced that there are now novel strains of yeast available only in dry format. Lallemand recently released Farmhouse, a non-diastatic saison strain, as well as NovaLager, a new, laboratory-bred non-GMO hybrid Saccharomyces pastorianus strain that produces clean lagers at high temperature and in short periods (read more about NovaLager in the sidebar below).
For brewers wanting to make sour beers, but fear their brewing equipment will be contaminated by bacteria, Lallemand also manufactures and markets two souring yeast strains. WildBrew Philly Sour is a strain of Lachancea yeast that was bioprospected (found in nature, isolated, and propagated), while Sourvisiae is a gene-edited strain of Saccharomyces cerevisiae. Both Philly Sour and Sourvisiae produce lactic acid and ethanol in the fermenter, thus eliminating the need for a kettle souring step in production of quick sours. These new strains are relatively sensitive, so the risk of them contaminating brewing equipment is low; more traditional brewing yeast strains will overpower them. Read more about their use in this “Tips from the Pros” column.
Fermentis also has SafBrew BR-8, the world’s first dry Brettanomyces strain. The particular strain is non-diastatic and is therefore good for bottle conditioning without risk of over-carbonation or gushing.
As costs keep increasing for commercial brewers, it is reasonable to assume more of them will switch to dry yeast because it is less expensive and easier to ship and store. Homebrewers will benefit from this as even more dry yeast strains become available to homebrewers as well.
It is, in a way, a return to historic brewing. Early beers had fermentation initiated by dipping the “magic stick” into the wort. And even today, many farmhouses in remote areas of Norway and Lithuania use a kveik ring made of strung together wooden blocks to inoculate brews and store yeast for future batches. Through millennia of domestication, brewing yeast has become very robust; it wants to make beer and dry yeast is as good at it as liquid yeast is.
“Don’t be scared of dry yeast. And don’t overthink it,” advises Conn.

Mythbusting: Dry Yeast Edition​

Myth: Dry yeast is lower quality since it is dead.
Fact: “Dry yeast is not dead. It’s in a dormant state,” Lallemand’s Senior Key Account Manager Brian Perkey says.
“When making active dry yeast, the drying process takes place right after the production of the new yeast biomass” says Jan-Philippe Barbeau of Fermentis. “Between 70% and 95% of this biomass is preserved through the drying process . . . On rehydration (in wort), the dry yeast is returned to its initial state. Only the most extreme conditions will affect (the yeast’s) viability.”
Myth: You must rehydrate dry yeast prior to pitching.
Fact: “This recommendation came from data from dry wine yeast,” says Eric Abbott from Lallemand. “For beer, there is no significant difference between rehydrating and dry pitching.” While dry yeast suppliers say homebrewers can rehydrate if they wish, this seems to be the result of reluctant acceptance that there is too much bias in favor of rehydration to overcome. Many homebrewing books still say rehydration is a requirement, but no dry yeast manufacturer actually recommends rehydration.
Myth: You cannot repitch dry yeast.
Fact: “Of course you can,” says Abbott, matter-of-factly. Many homebrewers choose to get more bang for their buck by cropping and repitching their dry yeast and some even report they get better flavor after two or three generations, just as they would from the second or third generation of a liquid yeast pitch. Of course, when cropping dry yeast, it ceases to be dry yeast, so many of the convenient benefits of dry yeast are lost.
Myth: You need to add nutrients and oxygen when pitching dry yeast.
Fact: “Oxygenation is not required for the first pitch,” says Barbeau. “Nutrients may not be essential, but they are a good idea.” But this is no different than liquid yeast. Zinc can be lacking even in all-malt wort and if using adjuncts, an addition of nitrogen will improve fermentation. This is a limitation of wort and is recommended regardless of whether the yeast is used in dry or liquid form.

The Amazing Science of Lallemand NovaLager (Sidebar)​

Only as recently as 2011, microbiologists determined that Saccharomyces pastorianus resulted from the natural hybridization of S. cerevisiae and S. eubayanus. Since this discovery, microbiologists have used genomic mapping to divide S. pastorianus into two lineages, being offspring of two separate natural hybridization events.
Group I strains, also known as Saaz strains, have three sets of chromosomes, one from S. cerevisiae and two from S. eubayanus. Group II strains, also known as Frohberg strains, have four sets of chromosomes, two each from S. cerevisiae and S. eubayanus. Armed with the knowledge that most commercial lager strains are Group II strains — because their proportionally greater S. cerevisiae genetic makeup makes them better at fermenting beer — scientists decided to improve on nature by making a new S. cerevisiae and S. eubayanus hybrid.
Lallemand’s LalBrew NovaLager is a S. pastorianus strain with four chromosomes, three from S. cerevisiae and one from S. eubayanus — a brand new Group III strain, also known as a Renaissance strain. The even greater contribution from S. cerevisiae means NovaLager can ferment between 50–68 °F (10–20 °C) while still producing clean lager flavors in a shorter time. The yeast was also bred to include technology from the wine industry to inhibit sulfur production. For homebrewers who cannot control fermentation temperature, NovaLager provides a novel solution. And it is merely the first of what may be a new frontier of interesting S. pastorianus yeast strains.

Written by Don Tse​

Issue: May-June 2023

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[MashBag]

Smashing read. Thank you.
Been a lallemand fan for a long time now, pleased they are still there. Their dry bacteria is very good. The crossover to sours sounds good too.

Better double check my olive oil nutrients too.

Cheers foxy