Yeast Washing. Is It Necessary?

[kabooby]

I agree. I think there are a lot of suspicions about the behaviour of yeast.
I have repitched lots of beers on to a full yeast cake and I have never had a problem. I know it doesnt mean much when someone else says they have never had a problem but its evidence enough for me to keep doing it.

Kabooby

 

[Screwtop]

I know that this thread is now morphing into a separate but related topic, but from what I understood the yeast behaves differently when there is no growth phase involved, and is not optimal for the fermenting process (ie there is such a think as over pitching).

As mentioned earlier, I always wash the yeast (in sanatised water) and pitch an appropriate amount (rule of thumb is about 1/4 for similiar OG and volume).

Reusing yeast should always be a process of proofing it in a starter no matter what the amount of yeast, get the yeast into growth phase, then pitch.

 

[chris.taylor.98]

I admit, I have never repitched onto a full yeast cake, but I am thinking this is a perfect excuse for a side by side experiment.

My concerns are that:
i) There is more than just healthy viable yeast left behind in the yeast cake, and the more you reuse it without processing it, the more likely you are to have some problems.

ii) Whitelabs seems to believe that "overpitching" can cause problems. From what I understand they are saying, the yeast will eventually lose condition, and you need new yeast growth to provide viable healthy yeast that are able to complete the fermentation cycle.

When pitching onto the yeast cake, there will be almost no growth ( ie new yeast cells produced ) so it mainly relies on the existing yeast cells that may not be up to the task.

I guess the question here is when using the whole yeast cake, because you have so much yeast, is the viability really an issue.

Again I could be talking completely out of my arse here but I know there are some much more experienced brewers than I that don't regularly follow this practice.

But I do absolutely agree you need to be very sure that you have enough yeast to do the job properly, and that is relatively rare for homebrewers to overpitch in general.

Equally of importance is the viability of the yeast, and ensuring that you have enough of the healthy clean yeast to get the job done, and I am not convinced that whole yeast cake fits this criteria.

 

[chris.taylor.98]

Reusing yeast should always be a process of proofing it in a starter no matter what the amount of yeast, get the yeast into growth phase, then pitch.

Absolutely screwy, the only way to know for sure the viability is to try it out ( hopefully in a yeast growth friendly environment ) before pitching it. Basically if in doubt do a starer.

The only time I deviate from this practice is when I string a line of 3-4 brews together and reuse the yeast within 2-3 weeks after collecting it from the yeast cake ( ie again I know where its been and what it has done in the very near past), and pitch the recommend amount ( ie not the whole cake so that the fermentation cycle includes a yeast growth phase ).

 

[Franko]

I agree. I think there are a lot of suspicions about the behaviour of yeast.
I have repitched lots of beers on to a full yeast cake and I have never had a problem. I know it doesnt mean much when someone else says they have never had a problem but its evidence enough for me to keep doing it.

Kabooby

+1 there brother well said

Franko

 

[rich_lamb]

Reusing yeast should always be a process of proofing it in a starter no matter what the amount of yeast, get the yeast into growth phase, then pitch.

Maybe this is a perception issue - but isn't using a starter technically the same as repitching the cake (or part thereof) from an earlier batch? I mean, if you think of the first batch as a large starter...
You've just proofed the yeast in this case.

Clearly you want to be careful to repitch within a short space of time, avoid repitching from a batch with high gravity (which is not my intention), and if you want to be nit-picky about it you could even try and measure how much yeast you repitch (which is also not my intention).

Screwy - what's your reasoning for mandating the growth phase?

 

[Screwtop]

Maybe this is a perception issue - but isn't using a starter technically the same as repitching the cake (or part thereof) from an earlier batch? I mean, if you think of the first batch as a large starter...
You've just proofed the yeast in this case.

Clearly you want to be careful to repitch within a short space of time, avoid repitching from a batch with high gravity (which is not my intention), and if you want to be nit-picky about it you could even try and measure how much yeast you repitch (which is also not my intention).

Screwy - what's your reasoning for mandating the growth phase?

Sorry B&T, didn't intend my post to come across as being mandatory. Making a starter is designed to build yeast numbers before pitching, smacking a smack pack is to test viability (fast - good, slow - not so good) there are obvious benefits in making a starter and limiting the amount of growth occuring in the wort (clean ferment).

I don't regard repitching as the same as making a starter, the yeastcake as a whole is not as clean and healthy as you would expect. Getting it going again prior to pitching is easy and ensures you have a good healthy pitch. With fresh yeast the number of viable cells is high and growth/budding happens quickly, allowing you to pitch a good number of cells ready to go to work fermenting your wort from the start.


Screwy

 

[Thirsty Boy]

I think that a lot of this stuff is a clash between what people know "works for me" and people trying to point out what they believe is "best practice" I strongly suspect (actually know because I am one of them) is that the same people who might say that you shouldn't pitch onto a whole cake, or that you should give the yeast a wash, or that you need to measure your amounts if you are re-pitching, etc etc .... sometimes do just the opposite, and it works out fine.

In my case, that doesn't mean that if someone asks a question about the best way to do something, I am going to tell them about my shortcut, I'm going to tell them about the best, safest, most proven way to do it. Then if they have heard about a shortcut that seems easier to them and like it wont hurt, they can try it if they want, but at least they will know its a shortcut. It might work out great every time - or it might not.

I also think that heaps of the "theory" around how to manage yeast re-pitching is based on the assumption that you are going to be re-pitch a lot of times. So while it probably isn't the best thing in the world to be re-pitching straight onto a yeast cake, it probably isn't going to ruin your beer - but if you pitch onto a cake, then pitch onto that one, then save a jar of the yeast and don't wash it - then leave it in the fridge for 3 weeks, then pitch it into a beer and pitch another beer onto that cake... you see where I'm going

or something like that anyway

Thirsty

 

[kabooby]

Good point Thirsty. Pitching onto the cake is not common practise here. But I have done and still do it at times. I did an English Summer ale with a fresh tube of WLP002 into a 2l starter and it fermented within a week. I had a cube of Mocha Porter and some empty kegs so I thought I would just chuck it on the cake instead because I was busy at the time. Ferment took off and was 90% complete within 24hrs. I was able to maintain the temp to 19C and I was still worried that the beer would have some esters from the fast ferment. I left it for a week to let the yeast finish up and it came out beautiful.

I think as long as you can keep your ferment temp stable and you have healthy yeast than it is OK. If you dont have good temp control than a fast ferment can get to hot, which would be a problem.

I think its one of those things that is not ideal but does work. You could probably do it 100 times and 99 times not have a problem.

Kabooby :icon_cheers:

 

[JoeG]

I can definitely add to the "works for me" side of things. I plan my beers in series, and reuse the slurry from the previous brew straight into the next. EG:

Plan 3 brews for 1056, generally starting with a SG about 1045 and getting stronger each brew. Culture up the yeast once (love that bit) and pitch first brew. When its done fermenting, keg, as soon as fermenter is empty grab a cup of slurry and wack it in the fridge while I wash and sanitise fermenter. I no chill, so i have the next brew ready to go as soon as the fermenter's ready. Yeast is back in the fermenter attacking the next wort within half an hour. Repeat process for next one - I normally only do this twice ie: 3 brews per yeast pack.

I do this all the time. I have yet to notice any problems with this process, in fact I would be hard pressed to pick the difference between the beer fermented with the first gen yeast and the one fermented with the 3rd gen yeast.

I have also just dumped the next wort straight onto the yeast cake of the previous quite often too. I'm either feeling lazy or its for a high gravity beer. I have never had any issues associated with overpitching with this process. Again, I would be hard pressed to pick the difference between first generation culture, re-pitched slurry or dumped straight onto the whole yeast cake.

Things to note: the yeast slurry I re-pitch is always used straight away, its never out of the fermenter for more than an hour. I only repitch twice before going to a fresh yeast.
As has been stated earlier - if you keep repiching using this method, or store unwashed slurry for any length of time, you could be heading for trouble.

 

[Beer&Kebab]

Years ago when I had more money and less time I used to buy the ESB (ST Peters) Fresh Wort Pilsener Kits exclusivley.. I would buy up to six at a time and 1 whitelabs yeast.. I would culture the yeast for the 1st brew and pitch.. For each of the 5 consecitive brews I would just throw the wort kit straight onto the yeast cake.. Not even cleaning the fermenter.. This was all done in a temp controlled fridge. I was hard pressed to notice any difference between 1st and last batch.. It seemed to me that the last might have been slightly more hoppy.. The most I ever did was 6 iin a row.. Though usually only 3... Sure there are inherent risks.. I took them and never regretted it..

 

[Screwtop]

Had some PM's asking about what to keep and what to discard when washing yeast, these pics should help explain:




The layer to keep is the second layer up from the bottom (yeast) the stuff on the bottom is often hard to see unless you look through the bottom of the vessel (pic on right), it is the heaviest of the crud. All above the yeast goes, the liquid and the layer below this, syphon off the yeast leaving the rubbish on the bottom then repeat the washing process by adding the yeast to more cooled boiled water.