Greg Hughes Dried Yeasts are not suitable for reuse

[rank_frank]

I've reused S-04 and W34/70 both with good results. The S-04 was an existing yeast cake that I repitched onto whilst the W34/70 was stored for a couple of weeks in kilner jars in the fridge. I'd do it more often but I don't brew regularly enough to make it worthwhile.

 

[jceg316]

I have reused dry yeast successfully. I have reused a lot of the Fermentis range and some MJ yeast and made great beers with it.

 

[Portreath]

I've not done this yet, but it's something that I would like to know more about, and possibly do it from my next brew day.

 

[peebee]

@IainM wrote earlier in this thread:

… I get that after fermentation the cells might not be in the best condition, but why would that apply to dry yeast and not liquid yeast? ...

I find that pretty rude, given that the immediately preceding post said:

… Manufacturers of dried yeast have to put a bit more effort into preparing the yeast for a tough process (i.e. the drying). ...

Why not question the preceding post rather than blatantly ignore it? How much of that attitude is actually going on here? There are novices reading this thread that will take away the idea that reusing dried yeast is completely without consequence.

It's not. You have to accept the (quite possibly slight) risk and weigh it against the savings (bearing in mind beer making doesn't just involve money, it involves personal time). But of course, if it does go wrong because of the yeast how do you figure that out? Easier just to scream "infection!", tip the beer away, and carry on as before.

Personally I'd never reuse dried yeast, but, with some specific exceptions, I normally use "liquid" yeasts now anyway.

 

[MyQul]

It also appears that dry yeasts aren't as microbiologically pure as liquid yeasts.

YEAST RACIST!!!!

 

[IainM]

@IainM wrote earlier in this thread:

I find that pretty rude, given that the immediately preceding post said:

Why not question the preceding post rather than blatantly ignore it? How much of that attitude is actually going on here? There are novices reading this thread that will take away the idea that reusing dried yeast is completely without consequence.

It's not. You have to accept the (quite possibly slight) risk and weigh it against the savings (bearing in mind beer making doesn't just involve money, it involves personal time). But of course, if it does go wrong because of the yeast how do you figure that out? Easier just to scream "infection!", tip the beer away, and carry on as before.

Personally I'd never reuse dried yeast, but, with some specific exceptions, I normally use "liquid" yeasts now anyway.

It wasn't my intention to ignore your post, I was just finishing a post I had already started to write and then got side-tracked. Of course, re-using any yeast is not completely without consequence, but I don't see why dry yeast is particularly special. Sure, the drying process is going to have an effect, but if anything it's the liquid yeasts that have a rougher ride, losing 20% viability per month if chilled compared to 4% for the dried stuff. While Greg Hughes is pretty good on the practical side of things, and his recipes are awesome, he does make a couple of technical mistakes in his book, e.g. p.22 "crushing allows the enzymes to be converted into fermentable sugars". What is that about? Another one, to do with yeast management, is that he recommends sprinkling dry yeast straight onto the wort without rehydrating first, even though there is plenty of evidence that this is not good practice and can kill half the cells. Other authors, such as John Palmer, Randy Mosher and Gordon Strong, don't make this mistake in their books.

I've never seen good evidence that dry yeast shouldn't be repitched without the same precautions as for liquid. Not to say there isn't any, just I haven't seen any, and what Sadfield found wasn't compelling by any stretch of the imagination. I've already alluded to a more cynical reason for why the manufacturers might recommend buying new yeast every time, and perhaps Greg Hughes has just taken them at face value. I would take him at face value, if he hadn't made other mistakes in his book. Someone I do respect on the topic of yeast, though, is Chris White, who wrote the most comprehensive book on the topic and is the founder and CEO of one of the biggest yeast manufacturers. In his book, he mentions many things, including rehydrating yeast, not needing to make a starter for dried yeast, and much more on oxygenation, fermentation and yeast handling, storage and growth. However, one thing he doesn't mention at all is anything about dry yeast being any different from liquid yeast when it comes to reusing it. Given the amount of detail in his book, I don't think he would miss something that basic... and indeed, of the many threads on the many brewing forums that talk about repitching dried yeast, they are dominated by homebrewers and professions saying that they do it and haven't had any problems doing it, which is also what I've experienced.

 

[Sadfield]

Another one, to do with yeast management, is that he recommends sprinkling dry yeast straight onto the wort without rehydrating first, even though there is plenty of evidence that this is not good practice and can kill half the cells.

Fermentis recently published a report debunking this assertion. https://fermentis.com/en/news-from-fermentis/technical-reviews/e2u-direct-pitching/

Someone I do respect on the topic of yeast, though, is Chris White, who wrote the most comprehensive book on the topic and is the founder and CEO of one of the biggest yeast manufacturers. In his book, he mentions many things, including rehydrating yeast, not needing to make a starter for dried yeast, and much more on oxygenation, fermentation and yeast handling, storage and growth. However, one thing he doesn't mention at all is anything about dry yeast being any different from liquid yeast when it comes to reusing it.

Although the website of the company he is CEO of, clearly does. https://www.whitelabs.com/yeast/dry-vs-liquid-yeast

 

[IainM]

Fermentis recently published a report debunking this assertion.

Although the website of the company he is CEO of, clearly does.

Thanks for the links. David Heath quotes research that claims that rehydration with agitation is worse than rehydration without agitation or direct pitching, which are both the about the same. The Fermentis page claims that direct pitching and rehydration with agitation are the same. Both of these conflict with a bunch of previous papers, done by independent scientists who don't have vested interests, as well as, for instance, this blog post by a homebrewing microbiologist with a microscope who repeats the experiments and gets the same results. That said, perhaps the more recent Fermentis results are because they have actually improved their yeast to the point that this is no longer an issue, just as how they and other dry yeast manufacturers have improved the purity and viability of dried yeast. The liquid yeast manufacturer, on the other hand, makes claims that liquid yeast has better purity and healthier cells than dry. Again, hard to assess their claims when there are conflicts of interest. I'd take the book with Zainasheff over the website. Regardless of all of this though, the vast majority of people who repitch dried yeast are very happy with the results. Some even prefer the second or later generations. In my opinion, this is very clear evidence that the statement "dry yeast is not suitable for re-pitching" is wrong. Just my opinion, you know what they say about opinions.
Peace!

 

[Drunkula]

Fermentis recently published a report debunking this assertion.

That article doesn't explicitly bebunk that it doesn't kill cells. And the article says at the end of fermentation with no mention of whether it took longer. It says dry pitching is adequate. If you really were advocating something you'd say it was as optimal. You need the full study, really.

I'm still more into this until something more specifically detailed comes along.
https://bkyeast.wordpress.com/2013/03/13/more-on-yeast-rehydration/

In case people didn't know you can speed up youtube videos by clicking the cog, then choosing speed - Heath's you can go up to 50% quicker on without the info going too fast, and start 20 seconds in to get past the the same tedious intro that's on every single video.

 

[Dutto]

This video on how to make a Yeast Starter has been on You Tube for over seven years and the lad uses a packet of Dried Yeast to make it.



Personally, I've only ever split a Yeast Starter made using this method on one occasion (for a brew planned a few days ahead) but I can't see why a Yeast Starter cannot be split, cultivated and used multiple times.

Alternatively, I'm reading something wrong!

 

[MyQul]

This video on how to make a Yeast Starter has been on You Tube for over seven years and the lad uses a packet of Dried Yeast to make it.

I havent watched the vid but I can see a wyeast smakpak (liquid yeast) at the back there

 

[Sadfield]

I havent watched the vid but I can see a wyeast smakpak (liquid yeast) at the back there

It's that pre-hydrated brand of dry yeast.

 

[BeerCat]

Am

YEAST RACIST!!!!

Every yeast has a right to beer. :-)

 

[trueblue]

By his own admission Greg Hughes plagiarised a lot of his book so this information may well have been just lifted from something he read somewhere. As has been stated the excellent yeast book makes no mention of not reusing dried yeast.

 

[MickDundee]

This video on how to make a Yeast Starter has been on You Tube for over seven years and the lad uses a packet of Dried Yeast to make it.

I’ve just watched the video and he’s definitely using liquid yeast

 

[Dutto]

Mea culpa.

It's years since I watched the whole video and I can only put down the misinformation to the fact that I only use reclaimed or dry yeast myself; but use the methods laid down in the video!

Sorry!

 

[Cwrw666]

Another problem with the Greg Hughes book is he only gives a fairly dismissive paragraph to BIAB. Considering it's the cheapest and probably the commonest entry route into all grain I find that unreasonable.
I've had great results from many of his recipes though.

 

[Sadfield]

It's also appears to be a bit of security blanket for many homebrewers. Doesn't really encourage or inspire brewers to create their own recipes like other authors do.

 

[stz]

On rehydration vs direct pitching I was always taught to rehydrate in water only and to always rehydrate. The reason given was direct pitching or rehydration in wort killed yeast cells as during rehydration they are unable to regulate the permeability of their cell walls and are exposed fully to any osmotic differential meaning sugar will kill a lot of them. The figure banded around was almost half compared to proper rehydration in water.

The room erupted with grumbling brewers who'd been direct pitching for years without any ill effect. The answer given was you were probably over pitching anyway, just because you get away with it doesn't change the fact there are observable differences in viability. One brewer said that he used to direct pitch when he knew that he wasn't around the next day because there would always be a longer lag phase compared to hydrating the yeast.

When Fermentis started saying you could direct pitch or hydrate in wort there was a little debate in the brewery. We stuck with hydrating in water because it works currently and isn't the end of the world. The instructions for pitch rates on yeast packets are pretty bad. Typically it'll quote 50-100g per 100L for an ale yeast and up to 300g per 100L for a lager. If you stick to the old rule of thumb of 1*10^6 per ml per degree plato you've usually got 6*10^9 per gram so 1g should do 500ml of 1.048, or 50g per 100L. The idea that figure is the low end and you should go double that suggests the packet is recommending over pitching from the get go. Why not direct pitch and kill half of it if you are already pitching twice the required amount of yeast? We've always started at 1*10^6 per ml per degree plato and typically decreased until we get where we need to be. Strain dependent, average is 0.7, lowest is 0.35. If your yeast handling is on point then you can pitch a lot less yeast than you'd think, if you've some gaps in your process over pitching hides a multitude of sins.

ANYWAY. This post is about reusing dried yeast. Why would I be wary? (I wouldn't). Keeping a wet culture going requires a holistic approach that means you have to be thinking about the long term health of the culture. When we say health I guess I'm rolling a few factors into one. Count, viability, purity and nutritional reserves. Dried yeast is supplied with the glycogen reserves to grow. Once it has finished fermentation the culture is depleted unless it had access to sufficient oxygen and free fatty acids during the growth phase. It might look alright, it might make it through another fermentation, but unless you can supply sufficient replacements during each fermentation, eventually the culture will show problems. If you've been keeping a wet culture going for generation after generation clearly your process is sufficient. Count and viability again, the proof is in a successful process, same with purity.

Dried yeast again hides a multitude of sins. It glosses over insufficient aeration or oxygenation. You can even bottom fill to avoid fob. It has a known count, viability and purity. If you aren't already in the business of keeping a successful culture going, I'd be wary of saying "you can reuse dried yeast without problem" because you don't know if there will be problems. A blanket statement that dried yeast is unsuitable for reuse is just wrong. Saying dried yeast can often be unsuitable for reuse because breweries which exclusively use dried yeast are often unaware of how their process lacks elements conducive to reusing any yeast is more apt. How is your aeration? We bottom fill. You'll probably have problems reusing that yeast. We've never had problems before. We'll you've never reused yeast before. Same for the other factors. It smacks of when people used to recommend that home brewers do not hydrate yeast. Not because hydration is bad, but because it is assumed that the hydration will be done incorrectly and result in more contaminated batches.

 

[Sadfield]

Great post @stz, but doesn't that make GH's comment valid in the context of the book being a very entry level affair? Given that he adds the caveat that dry yeasts are relative inexpensive (a point omitted from the OP).