Dry Pitch vs Rehydrating yeast

[BlackSands]

The mention of rehydrating yeast has come a few times on other threads so I thought the following might be of interest.   Out of curiosity I recently went back to dry-pitching for the last few brews and haven't noticed any discernible difference in my brews as a result though rehydrating might still perhaps be considered a 'better safe than sorry' option.... or not?'   

 

Brulosophy found:

"...[only] 40% of the participants, all of whom are experienced homebrewers and craft beer enthusiasts, were capable of discriminating a beer fermented with  rehydrated yeast from one sprinkled with dry yeast."

http://brulosophy.com/2014/09/15/sprinkled-vs-rehydrated-dry-yeast-exbeeriment-results/

 

And, and an experiment by Khris Lloyd that did lab-based yeast cell counts:

"Non-hydrated, direct pitched wort did indeed have a higher death rate than both the hydrated samples.
However, the loss was minimal in comparison to other sources reporting cell loss rates upwards of 50%.
The loss is significant enough, particularly when scaling to commercial sized batches that the slightly
higher loss should be accounted for depending on your desired pitch rate. For typical five or ten gallon
batches, homebrewers should not have concerns, specifically pertaining to cell counts, as the difference
in loss between the two methods was only five percent."

https://drive.google.com/file/d/0BzNmUGsHZf7dOTZzZF9aQVluZXM/view?usp=sharing

Edited May 16, 2019 by BlackSands

[Instigator]

Talking of cell counts, I've been curious as to whether there is any benefit to not just rehydrating, but creating a starter from dry yeast. There is a lot of discussion on this forum about under-pitching that caused me to wonder about this. I haven't seen anyone suggest it, so I presume it's not generally a done thing.

[Otto Von Blotto]

It's not usually done with dry yeast because it's generally cheap enough to simply buy another packet if more yeast is required. I used to do it though, because I reuse yeast from starters rather than fermenter trub. I also used to do it with lager yeast because it was a lot cheaper than buying more packets to get the large pitch amount. So it just depends on the situation I guess. 

I'm not particularly surprised at the brulosophy result given the strain of yeast they used. That stuff is a beast. Would have been more interesting to see what happened if they used a proper lager yeast though. 

[ChristinaS1]

7gm of kit yeast is enough to ferment the kit plus 1kg of brew enhancer. It could also handle 500gm of plain DME. Coopers dry ale yeast, which comes with the OS kits, is very vigorous and can ferment the kit plus 1kg of DME. I would not trust 7gm of the yeasts that come with some of the other kits to ferment 1kg of DME though. If you are using a 1.5kg tin of LME,  you need more yeast. 

When I only have 7gm of kit yeast available, but need more, I make a 1L Shaken Not Stirred starter with it the evening before. A 1L starter does not contain enough nutrition for a 10-11.5gm package of third part yeast, but it is perfect for 7gm.  There is a thread on how to make Shaken Not Stirred starters. 

@BlackSands: I have been rehydrating for years but am considering trying dry pitching again, but not 7gm of kit yeast. I'd use two packages of kit yeast (=14gm) or 10-11.5kg of third party yeast, into my typical gravity of 1.048-1.052. However, I would rehydrate any yeast known to have a long lag time, such as US-05, M44, and BRY-97. 

Cheers,

Christina.

 

Edited May 16, 2019 by ChristinaS1

[Aussiekraut]

39 minutes ago, ChristinaS1 said:

7gm of kit yeast is enough to ferment the kit plus 1kg of brew enhancer. It could also handle 500gm of plain DME. Coopers dry ale yeast, which comes with the OS kits, is very vigorous and can ferment the kit plus 1kg of DME. I would not trust 7gm of the yeasts that come with some of the other kits to ferment 1kg of DME though. If you are using a 1.5kg tin of LME,  you need more yeast. 

 

Silly question: Why is 7g not enough for 1.5kg LME? Does yeast stop multiplying before it runs out of food?

 

[Otto Von Blotto]

It can if you don't pitch enough. I think the message there is that there's probably more risk of it failing rather than that being a certainty. Also, maltose is harder work for the yeast than dextrose. 

Generally speaking the higher the OG is the more yeast should be pitched to ensure a successful outcome. 

[BlackSands]

1 hour ago, ChristinaS1 said:

@BlackSands: I have been rehydrating for years but am considering trying dry pitching again, but not 7gm of kit yeast. I'd use two packages of kit yeast (=14gm) or 10-11.5kg of third party yeast, into my typical gravity of 1.048-1.052. However, I would rehydrate any yeast known to have a long lag time, such as US-05, M44, and BRY-97. 

 

Yeah, rehydrating has been my habit historically.   I've only used kit yeast once this year and it was 2 packets dry pitched.  

I'm about to do a brew using M54.  I think I will err on the side of caution and rehydrate....  though I used it once before rehydrated and it was still an ultra-slow starter on that occasion -  2 days!  And actually, as it happens I ended up with a phenolic brew for reasons unknown.     I know you had a phenolic batch recently and expressed some concern about rehydrating at too high a temp ... I wonder... ?  

I've read recently of others only experiencing a 12 hour lag with M54 and some actually referring to it as one of their 'go to yeasts' so thought I'd take a punt and give it another try.   Maybe I just got unlucky that first time.  

[ChristinaS1]

1 hour ago, Aussiekraut said:

Silly question: Why is 7g not enough for 1.5kg LME? Does yeast stop multiplying before it runs out of food?

 

There is a great answer here to your question:

https://homebrew.stackexchange.com/questions/1812/why-is-it-bad-to-pitch-too-little-yeast

For convenience, I will copy it:

"Yeast produce different flavors during the various stages of their lifecycle. Underpitching lengthens their "growth" phase (maybe a better name is "division" or "budding"). The bulk of a beer's esters are produced during this initial stage, so extending this part of the lifecycle increases this sometimes undesirable quality.

Yeast need oxygen to bud. A homebrewer can usually dissolve enough oxygen into wort to facilitate four buddings. Once out of oxygen yeast begin consuming sugars. In this phase the yeast stores energy to sustain it during hibernation. Yeast will begin consuming the simple sugars moving to the more complex molecules as the easy to digest food diminishes. Once it is full of stored energy the cell shuts down and flocculates.

Underpitching can introduce an insufficient amount of yeast to entirely consume the entirety of the beer's fermentables. Your fermentation may not finish, or there could be enough food for an infection to take hold."

Everything in that answer made sense to me until the last sentence. I guess the author means that if the yeast stall, there could be enough fermentables left to feed contaminating microbes. I always thought the underpitching posed a risk for contamination at the beginning of fermentation, meaning a wild yeast might out compete the pitched yeast and dominate the fermentation. It never occurred to me that underpitching might pose a risk for contamination at the end of fermentation as well....Makes me wonder if that is what happened to my Cluster Bitter SFWH experimental batch.

Cheers,

Christina.

Edited May 17, 2019 by ChristinaS1

[Worthog]

I've always been happy to sprinkle 2 sachets of  Kit International yeast. I still rehydrate US-05 for @ChristinaS1 reason.

I'm a bit sad I have used all my stocks of KitInt yeast; love it, especially in winter for it's low temp bottle carbonation.

I then harvest them for 5 to 6 generations of re-use.

Sprinkling is so much easier than faffing around dehydrating. The article above is good info to know.

Cheers

[BlackSands]

28 minutes ago, Worthog said:

I'm a bit sad I have used all my stocks of KitInt yeast; love it, especially in winter for it's low temp bottle carbonation.

One reason I often use Nottingham... and more recently M42 which also appears to keep chugging along during the colder months.  In fact some say they're the same strain. 

As an interesting comparison, we're now experiencing cooler temps here, with the warmest days peaking around 17 - 18ºC and of course much cooler overnight.   I bottled a batch 13 days ago fermented with M36 which is still not fully carbonated.  I've sinced moved them indoors and after just one day the PET's now feel noticeably firmer when squeezed.   In contrast, I bottled another batch fermented with M42 2 days ago and already those PET's have firmed up almost as much as the M36 batch - clearly no need to move them to somewhere warmer!  

 

    

[Otto Von Blotto]

That probably explains why I get a bit longer lag times when I inject pure oxygen into the wort at pitching time - there's more of it to use up. It might only facilitate an extra budding but may be why the fermentations are usually over pretty quickly. I haven't noticed any added esters or whatever either, if anything the beers have been a little cleaner tasting. 

[ChristinaS1]

6 hours ago, Worthog said:

I've always been happy to sprinkle 2 sachets of  Kit International yeast. I still rehydrate US-05 for @ChristinaS1 reason.

I'm a bit sad I have used all my stocks of KitInt yeast; love it, especially in winter for it's low temp bottle carbonation.

I then harvest them for 5 to 6 generations of re-use.

+1 on the kit International yeast. It is great stuff. As you say, great for bottle carbonation at colder times of the year, but I think the flavour is great too. I use it to ferment all of my APAs, which probably 80% of what I brew, and my annual batch of Oktoberfest. The only times I don't use it is when I am brewing an ESB or a Stout....Not into Belgian styles.

Interesting to hear that you have re-used the International yeast 5 to 6 times Worthog. I have never gone past three, and usually re-pitch the day after harvesting slurry from the bottom of the fermenter. Are you using the sloppy slurry method?

Cheers,

Christina.

[ChristinaS1]

6 hours ago, Otto Von Blotto said:

That probably explains why I get a bit longer lag times when I inject pure oxygen into the wort at pitching time - there's more of it to use up. It might only facilitate an extra budding but may be why the fermentations are usually over pretty quickly. I haven't noticed any added esters or whatever either, if anything the beers have been a little cleaner tasting. 

Yes, I remember being puzzled by your reports of longer lag times, back when you first started using O2, but this explains it. 

Cheers,

Christina.

[Worthog]

29 minutes ago, ChristinaS1 said:

....Interesting to hear that you have re-used the International yeast 5 to 6 times Worthog. I have never gone past three, and usually re-pitch the day after harvesting slurry from the bottom of the fermenter. Are you using the sloppy slurry method?

Cheers,

Christina.

Yes, I simply 2/3 fill a PET at end of bottling, cap it and put it in the fridge.

When I reuse it my only problem is trying to prevent gushing, which it is apt to do, while I try to pour off some beer and swirl it a little. I usually end up using about 200ml into the wort.

Truthfully, in the past I have only stopped harvesting it after I have commandoed hops, which I now never do.

I agree with you about the taste. If I could buy it I would use it. Seems very similar taste to US-05.

Cheers

[ChristinaS1]

16 minutes ago, Worthog said:

Seems very similar taste to US-05.

Fermented at 18C, which is what Coopers recommends, I totally agree: very similar flavour to US-05, plus it has a shorter lag time, and settles and clears more quickly. No reason to pay $5 for US-05 if you have the International yeast available for free.  If Coopers sold it in 14gm packages, I would also pay money for it. 

If fermented warmer, I suppose it might get a little fruity, due to the lager portion being fermented so much warmer than it usually is. Since I have a brew fridge, that is a non-issue for me though.

Cheers,

Christina.

Edited May 17, 2019 by ChristinaS1

[Pezzza]

11 hours ago, ChristinaS1 said:

I would not trust 7gm of the yeasts that come with some of the other kits to ferment 1kg of DME though. If you are using a 1.5kg tin of LME,  you need more yeast. 

 

 

Hey Christina,

I agree with what you are saying (and really like your scientific approach to everything we do!) but my experience has been with Coopers yeast even when I am adding loads of LDME it seems to work out fine... with good hygiene.... I guess it may also depend upon what flavor result you are chasing too hey?

Cheers... luv yer sci focused posts!

BB

[porschemad911]

5 hours ago, ChristinaS1 said:

+1 on the kit International yeast. It is great stuff. As you say, great for bottle carbonation at colder times of the year, but I think the flavour is great too.

Me too. Also extremely versatile in terms of the styles it works well in. Also pretty alcohol tolerant, it got my mead to over 14% ABV.

Cheers, 

John 

Edited May 17, 2019 by porschemad911

[Worthog]

I'm about to put down my first Lager for the season.

I am using 2 x 11.5g of S-23 in 23L of wort at around SG 1.040.

The wort temperature will be approx 15c to start. I will then reduce to 10c over 12 hours or so.

My question is; what temperature should rehydrated yeast be when adding to wort? I usually ensure less than 10c differential between wort and yeast.

Is this necessary with S-23?

Cheers 

[Shamus O'Sean]

I rehydrate my yeasts in 30°C water.  By the time I pitch it would be very close to ambient temperature.  Worked fine so far.

Having said that I pitch slurry from a previous batch straight from the fridge into 20°C wort.  That works fine too.

[Otto Von Blotto]

It's best to be as close to the wort temp as possible but they reckon within 10 degrees is ok. Personally I wouldn't go any higher than 5 above. Temperature shock is a risk in this scenario which is why you want the yeast and wort at the same or similar temps. This doesn't appear to be the case with cold yeast going into warmer wort as evidenced by the number of people having success with that method.

If your rehydration temperature is significantly higher, small amounts of water or wort can be added to the rehydrated yeast to gradually bring the temp down prior to pitching.

[BlackSands]

Interestingly a couple of Brulosophy experiments showed different outcomes for yeast pitched cold vs warm depending on the yeast.  The ale yeast they selected (WLP090) produced no detectable difference at the glass, however the lager yeast (S-23) did.  Though I did note the temperature difference was very wide for the lager yeast - 9º and 27ºC.

[Otto Von Blotto]

I didn't really notice any difference in flavour from pitching yeast cold (talking slurry from starters, not rehydrated dry yeast) instead of letting it warm up first either, but it did consistently take off faster. 

It would be sitting somewhere between 0 and 5 degrees when it's pitched into the wort, which has been anywhere from 10 to the high 20s. I prefer the wort to be at or a bit below ferment temp but it's not always achievable. 

[BlackSands]

I generally pitch at whatever temperature my wort ends up at!      That's anywhere between 20 - 24ºC usually.   Often it's slurry straight out of the fridge which seems to get off to a fast enough start going in cold.