Yeast Farming

[chiller]

I have been asked on a number of occassions to explain my method for yeast farming -- Well it is nearly 40c outside and even I consider it is too hot to fire up the NASA burners so I hope you find this material useful.

Yeast and homebrewing are almost hand in hand as mystery black arts. And there is a mountain of repeated information that is never tried just repeated.

Yeast is a great thing and it has a strong need to make beer. It is no where near as delicate as people try to make out and will survive for a very long time with a very small amount of preparation.

Yeast from the secondary are often the slower flocculators and as such may not be true to the character of the initial pitching that is comfortably sleeping in the primary.

The day before you intend to remove the beer from the primary prepare 2 litres of sterile water [boil for 15minutes is enough] and allow to cool in the fridge in a sealable PET soft drink bottle will do.

Obtain 2 500 ml jars, a clean sanitised beer glass and 3 50 - 100 ml sample vials.

Transfer the beer off the cake and remove all the beer [not the yeast] Pour 500ml of your sterile water into the fermenter and give it a very good swill around to mix the yeast and water, now with the sanitised beer glass collect enough of the yeast solution to almost fill one of the jars. Shake it really well and lightly seal it and set it in the fridge for about 10 - 15 minutes. The heavy material will drop and you can now pour the top 3/4 of the liquid into the other jar and top up with sterile water.

Shake and set aside for 10 -15 minutes and in that time sanitise the other jar. After the 10 minutes pour the milky yeast liquid into the 2nd jar and top up with sterile water. Shake and set aside for 10 -15 minutes and in that time sanitise the first jar. Now pour the top 3/4 of the liquid into the other jar and top up with sterile water. Shake and set aside for 10 -15 minutes and in that time sanitise the 3 small sample jars.

Fill the sample jars 3/4 full with the milky liquid remaining, cap these and place in the fridge.

What remains in the larger jar can be used for your next brew [make a starter] or discarded.

Next stage is to let the yeast settle out in the sample jars for 24 - 48 hours. You will now have a compact yeast layer and reasonably clean liquid on top. Remove the lid and pour off most of the liquid and replace with your sterile water. Shake well and let settle again for 24 hours. The liquid will now be quite clear, pour this off and replace with sterile water and return to the fridge. Check your samples over the next week and if the water shows any discolouration replace it with fresh sterile water.

These samples will remain viable for at least 12 -- 18 months and maybe longer. I have used a Scottish ale yeast kept in my yeast farm that was dated 3 years old. It fired up over 2 days stepping up from 50mls to 150 mls to 500 mls.

I have used yeast over many generations maintained in this manner with absolutely no changes in character. Far bejond the mythical oft repeated homebrew law of 3 generations. For interesting reading on yeast examine what the late George Fix had to say on the topic.

The only danger and it is real is the danger of infection when harvesting yeast. Most All Grain brewers are competent at sanitation and the problem is small.

Pint of Lager has at one stage on either this forum or another posted a very practical guide to sanitation.

Even if you only brew once again from each of the samples over the next 6 months you will be using your yeast more efficiently. Don't forget when you use the last sample repeat the procedure. Another three samples will be waiting when you need them. You will probably have 3 -- 4 favourite yeasts you use on a regular basis and this method will ensure you keep a healthy supply ongoing for a very long time.

Yeast are your friends.

Steve

 

[JasonY]

Well done chiller, excellent guide. I am certainly not at this level in terms of my yeast harvesting practices. I have been just storing the slurry in the primary for future brews or splitting the original starter.

One thing I don't do and perhaps you can shed some light on the benefits is the whole stepping up thing. I just make my 1L starter and turf the yeast in and wait for the action to start. What is the benefit in doing say a 100ml, 500ml, 1L step? I just figure if I am boiling the DME I may as well do the whole 1L so I don't have to boil repetitivley.

 

[chiller]

The short unscientific answer is that if you give a relatively small number of yeast a larger [compared to their number] amount of starter they can get rather lazy and often only work on what they need and not reach the sort of numbers requires for a brew. They then behave a lot like Aussie drinkers after their fill and fall asleep on the bottom of the bar/starter.

Adding from my collection about slightly bigger than a thumbnail amount of yeast to 50 mls ensures that they will get into the reproductive stage quickly without moving to beer making stage. Adding more starter to the 50 mls at about 24 hours keeps them in the making yeast stage. If I time it right I will step up to 1 - 2 litres at the point the yeast numbers are approaching the maximum for the size of the starter.

Steve

 

[jgriffin]

I've used similar methods before with great success. After a few cycles of fresh water, i've ended up putting the yeast slurry back into the white-labs tubes that i have around. You can easily get 1/2 dozen of these tubes packed with 3 times that amount of yeast you get when you buy a tube, and i've had no problem kicking them off again 6 months later.

 

[spog]

great informative post,chiller,ihave been doing the same as jy,and have yet to find a problem,i have only recycled ? my yeast,s no more than 3 times because i was under the impression that after this time the yeast basically ****,s it,s self. but now it has finally dawned on me that ,yes yeast IS a living organism and if looked after and not basically abused will continue to grow,or be useable.

 

[Gulf Brewery]

Hi

There are a couple of points that have come out that need a bit of clarification.

The first is stepping up the wort. One of the main reasons is so that the yeast will outnumber the bacteria in the wort and will dominate. If you pitch x amount of yeast into 50ml vs the same amount into 1 litres, then in 50ml they will a lerger percentage of the organisms in the beer.

The second is re-using yeast. Yeast will mutate over successive generations and also the bacterial and wild yeast count will increase over time. Its safer to replace the yeast after a few generations rather than risk infection and/or off flavours.

Cheers
Pedro

 

[sosman]

The first is stepping up the wort. One of the main reasons is so that the yeast will outnumber the bacteria in the wort and will dominate. If you pitch x amount of yeast into 50ml vs the same amount into 1 litres, then in 50ml they will a lerger percentage of the organisms in the beer.

I take it that is assuming (me not being a micobiologist) that either:

a) The bacteria are in the wort (vs with the yeast), otherwise the ratio will be the same when pitched. Since I boil wort for starters it is presumably sterile relative to yeast slurry.

B) The bacteria multiply faster so you want the yeast to start producing alcohol soon to limit growth of bacteria.

Anyway, this is more curiosity than anything, I generally step up (but wouldn't bother if I didn't have to).

 

[pint of lager]

Sos,

Sterile means there are no bacteria, wild yeasts or spores. This is achieved by putting the sample in a pressure cooker or autoclave. Boiling does not kill all spores.

For making up starters, you can boil wort for 20-30 minutes, cool, and use straight away.

Also, bacteria and wild yeasts muliply at about 10 times that of our brewing yeast. So if you start off with a small infection and a small amount of yeast, the unwanted yeast or bacteria quickly multiply to levels that are detectable in our beers.

Brewing yeast does change the conditions to be unfavourable to bacteria. pH decreases, alcohol is produced and the wort becomes anearobic (no oxygen.) All of these limit the growth of some sorts of bacteria. Be aware that after fermentation, there is alcohol and long chain sugars in your beers, both of which are high energy sources to some bacteria.

 

[sosman]

One crazy idea I was pondering was to drip feed a starter.

The idea would be to start out with say 50ml then time your dripper so it was up to 2L over 24-48 hours. Its probably more mucking around than just stepping up but I was thinking it would provide a continuous feed of fresh nutrient to the multiplying yeast.

Anyone work in a hospital? All I need is one of those hooks on wheels thingy and put my yeast on an intravenous drip.

 

[pint of lager]

Sos, this is not a crazy idea, this is how companies make yeast in commercial quantities.

The yeast is drip fed nutrients and oxygen in the right mix and kept in suspension by continuous stirring. I suppose the manufacturers have ways of measuring growth rates, dissolved oxygen and other parameters and adjusting the drip rate to match.

You can buy a periastaltic pump or a dosing pump off ebay. They come up every so often in the "lots more" category, in either lab gear or medical subcategory.

 

[Backlane Brewery]

FWIW, this is from the commercial brewers FAQ section of the White Labs site (see links page)

How many generations should I use my yeast?
We recommend 6-10 generations per strain. Three main reasons yeast should be replaced on a regular interval are bacterial contamination, yeast cell mutation, and yeast fatigue.
Bacterial contamination is largely responsible for off flavors. Bacteria grow at an exponential rate in comparison to the yeast.
Yeast cell mutation. Yeast cells will adapt to their environment, this could dramatically or subtly change the characteristics of the beer.
Yeast fatigue. Beer is a hostile environment for the yeast. Healthy yeast requires oxygen and food (malt). CO2 and alcohol are detrimental to the overall health of the yeast.

 

[Sean]

Of course how many generations you can get depends a lot on the yeast. Some strains are very stable and you can reuse plenty of times with little work and no problem. I've gone to 13 generations with a yeast just pitching each brew with the slurry from the previous with no appreciable change in character. That was a good traditional ale yeast sourced in a jam jar from a pretty traditional friendly micro-brewery, who in turn had sourced it from a very traditional old family brewery (the only one in England still with a thatched roof). It certainly hadn't been anywhere near a lab in 20 generations, probably much longer.

On the other hand, some yeast strains aren't even stable for more than three or four generations in their own originating breweries without significant lab work.

Additionally, if your brewery is significantly different from the source you are likely to speed that up - Marstons claim their yeast changes after a single generation when used in square fermenters instead of the Burton Union sets, which is why they spent such a huge amount of money building a new Union set a few years ago.

Some larger breweries never reuse yeast out of their own breweries - all the yeast is supplied afresh each generation by their labs. I know Whitbread worked like this, and I presume the same is true of many others.

 

[roach]

Sean,
This is an interesting topic and in the context of a homebrewer who has good yeast farming techniques, I would be interested to know your experience, in what yeasts become unstable after 3 or 4 generations?

Such empirical evidence from brewers who practice good technqiues, would be valuable, as there is seems to be of conflicting info on this topic of yeast farming and generations.

Roach

 

[wee stu]

Dane - how about airlocking this thread?
Chiller's initial post was highly informative, and one which should be easily got hold of for anyone struggling with the concept.

 

[Batz]

Done stu

 

[BJCP Education Director]

Ive been working in a lab with yeast for about 10 years now. The problem with yeast farming is that you must insure the quality and health of the yeast. The most know way to do this is to 'acid wash' your yeast. Basically, by washing your yeast in acidulated water you kill a lot of the bacteria. This is because the cell wall of the bacteria are different from yeast however the problem is that is reduces the viability of healthy yeast. The new method is to use Sodium Chlorite (NOT bleach, thats Sodium HYPOchlorite). Basically, it oxydizes the crap out of the bactera making them rupture.

Here is a link going more in depth:
http://www.birkocorp.com/brewing/yeast.asp

Here is a great little lab protocol manual from a really good yeast farming company:
http://www.brewingscience.com/Brewers%20La...%20Handbook.pdf

 

[Hoops]

Excellent explanation there Chiller.
Printed and in my HB folder.

I have a question on this topic that I have been contemplating.
I currently have a large bottle of Chimay (door prize from HB club) and want to build up the yeast and split into samples for myself and other club members. My question here is do you think I should:

1. Make a starter, pitch in a brew then harvest yeast?

OR

2. Make a large starter and split that into samples?

Hoops

 

[BJCP Education Director]

Eventhough I would with yeast on a daily basis I still prefer buying my yeast if I can. The problem is that the yeast in the bottle has been stressed not only from the fermentation but also from sitting in the bottle surrounded by all the alcohol. When I culture yeast, I plate it on Wort-agar plates, pick a single colony and grow it up. Doing it this way ensures that 1) I will have a pure strain and 2) wont have any infections.

You can get he Chimary strain from:

White Labs WLP500 Trappist ale
Wyeast 1214 Belgian ale

 

[Trough Lolly]

Here is a link going more in depth:
http://www.birkocorp.com/brewing/yeast.asp

Thanks for the interesting read - I've added it to Steve's article and kept a hardcopy in my folder...I already have the protocol manual Regarding Chlorine Dioxide, is it readily available in bottles or is this stuff unstable chemically - ie, it degrades to its constituent elements when stored?
Regardless - I'm gonna stick to Steve's KISS article and if I get daring, I might have a go a yeast washing - jeez they're gonna need bloody small clothespegs!

Cheers,
TL

 

[Hoops]

Similar procedure here for freezing test tubes of yeast