Yeast Farming

[chris.taylor.98]

well the yeast that you have already brewed with actually be better second or third time around if you can keep reusing it every couple of weeks.

( some micro breweries even go up to 10 times or more, but you want to make sure you have good sanitation practices to do this ).

If you want a better guide to the amount of yeast you need to pitch, try this calculator:

http://www.mrmalty.com/calc/calc.html

Although I usually find it a bit on the conservative side.

Yes you can go ahead and cold shock, then poor the liquid off the top and just pitch the slurry. Although I usually try and time my starter so that it is quite active when I'm ready to pitch, then pour the whole thing in. This results in really short lag times.

With the way that starter took off I don't think you will have any problems with lag time.

Generally you either:
i) time the starter so that the yeast has multiplied out and is just starting to take off.
ii) if you need a particularly large starter and/or don't want the starter wort in the brew then let the starter ferment out and cold shock and add just the slurry.

When you have a fairly clean starter wort ( as you do with the DME ) you can pitch the whole thing with out too many worries.

 

[matti]

I brewed a lager earlier this year, Fresh Wort Kit, and harvested the yeast from primary.
I pitched two sachets of rehydrated W34/70.
This was harvested from primary after ten day as the beer was racked.
The yeast smelled beautiful and I used this for my my last lager which I racked today.

I managed to harvest some more but not sure if this a good idea.

I am not sure if lager yeast is suitable to harvest if it has been in primary with a bit of trub.

Will washing the yeast sort things out?

Would the yeast have mutated sitting in the trub and not worth harvesting?

I understand that it is recommended that you should only harvest yeast that has had a clean ferment.
This time it may not be the case, since there was a presence of sulphur.

Cheers
matti

 

[skeet]

thanks for your help

a good easy understood guide.

 

[Hefty]

I've just tried harvesting for the first time from a brew using us-05. What I ended up with were 3 small samples of thick creamy slurry. Is this correct or should I have added cooled sanitised water one last time to make more of a milky/watery sample?
I figure either way it will settle out to a thick deposit at the bottom, is there any reason more water above the deposit will be beneficial? I'm keen to know so I can make sure I'm not ruining these samples.

Cheers!
Jono.

 

[Lobsta]

hmm, i have a mate at uni with access to the microbiology labs... could be useful. sterile, temp controlled growth fridges. sterile agar plates... hmm...

Lobby

 

[Sprungmonkey]

Is there any reason why people use slants (agar media with nutrient) to innoculate yeast rather than just using a broth with nutrient or just peptone water? Wouldn't it eliminate having to plate onto agar (or in a slope tube)?

I havn't done any culturing of yeast before but had a little bit of experience innoculating food pathogens for identification. I have always just used a broth and transfer from one broth to the next.

 

[olskoolsoulja]

germs cant grow in agar

 

[Sprungmonkey]

Im not sure if this is correct. Agar is justed used as it allows for a solid medium to grow on. What grows depends on the nutrients and environment (eg temp, pH etc.). If bacteria didn't grow on it then we wouldn't have to have such aspetic techniques.

 

[chiller]

Is there any reason why people use slants (agar media with nutrient) to innoculate yeast rather than just using a broth with nutrient or just peptone water? Wouldn't it eliminate having to plate onto agar (or in a slope tube)?

I havn't done any culturing of yeast before but had a little bit of experience innoculating food pathogens for identification. I have always just used a broth and transfer from one broth to the next.

With the Agar the yeast live basically on the surface and use only that nutrient that they contact. They go into hibernation for the want of a better word because of a lack of nutrient to go into a full reproduction cycle.. If you introduce them into a fluid medium that has a nutrient source they can reproduce until they exhaust the nutrient supply. The can easily, physically spread through the medium. Using a slant you put them "to sleep" for 6 months - 2 or more years. As soon as you introduce a nutrient rich solution they revive and begin their work.

Darren is probably the best qualified in a technical sense to give the full story on the whys of "small critters"

Steve

 

[Sprungmonkey]

Okay. Just deciding on which way to go.

How much shelf life do liquid yeast companies have on their cultures -- 6mths?

 

[chiller]

Okay. Just deciding on which way to go.

How much shelf life do liquid yeast companies have on their cultures -- 6mths?

I'm not certain but the figure is often date of manufacture. I popped a 5 year old Wyeast Belgian the other day and it was ready to go into a starter within 24 hours.It has already brewed a beer and will be harvested for "many" to come. I have also used WhiteLabs vials that are 2 - 3 years old and had then up and started within a short space of time. I don't know for certain but Lager yeast seem to me [and this is only my observation] to be less robust. Better to get fresh if you can.

 

[chiller]

germs cant grow in agar

That seems an interesting reply. I will give you the benefit of the doubt that you have a broader knowledge on this matter and accept that you are frustrated at our complete lack of comprehension on this topic and thus have replied in the curt manner you have - or - you don't have a clue and your post is a waste of time.

Apparently there is an Agar medium that things don't grow on and this could be the point of your post but without explanation it leaves me wondering at your reply.

In the topic we are talking about yeast and just about everything else will grow on the medium so care has to be taken to transfer only the yeast to the slant.

 

[quadbox]

I'm not a microbiologist (more into the myriad ways of making things go boom ), but as I understand it the second major reason for culturing on agar instead of in a liquid medium is because the lack of contact with nutrients limits the amount of reproducing the yeast actually does, and so you dont constantly increment the generation count. For all intents and purposes no matter how many times you transfer from slant to slant over the course of a few years you've still got pretty much generation 0, with sfa mutation.

Whereas if you split and grow starters, you're pretty much incrementing the generation every time, as there's a significantly larger (and more active) number of yeast cells in play in each starter, even if it's only a very small starter

 

[Sprungmonkey]

Interesting -- not too sure. Slant to slant, inoculation broth to inoculation broth, tomato tomato. Don't know if there is any difference in generations and possible mutations. Activity of the yeast should be limited purely due to refigeration storage. I can however see your point regarding nutrient availability on slants. I don't know how critical it is at refrigeration temps. I might have to try both and look at the viability of yeasts slant vs broth.

 

[chiller]

Interesting -- not too sure. Slant to slant, inoculation broth to inoculation broth, tomato tomato. Don't know if there is any difference in generations and possible mutations. Activity of the yeast should be limited purely due to refigeration storage. I can however see your point regarding nutrient availability on slants. I don't know how critical it is at refrigeration temps. I might have to try both and look at the viability of yeasts slant vs broth.

Let us know in about 5 years. That is the oldest slants i have that I have revived and used.

 

[Sprungmonkey]

Going to a liquid yeast night at brewers choice on wednesday night wiht hte guys from white labs
Ill ask them and let you know.

 

[chiller]

Going to a liquid yeast night at brewers choice on wednesday night wiht hte guys from white labs
Ill ask them and let you know.

You will really enjoy the night I attended one with Chris white from Whitelabs and at another time Dave from Wyeast. Very informative.

 

[pint of lager]

Yeast farming is one facet in brewing that some people get very involved with.

Growing yeast on agar in petri dishes is done to isolate single colonies. At the same time, if a sample is infected (yes, germs happily grow on agar) yeast colonies can be removed from the infected plate and restreaked on a fresh uninfected plate. This process demands sterile conditions. The macro shape of the yeast colony can also be used to distinguish good and poor quality yeast. The process requires a high level of skill and knowledge. Many different yeasts can be kept on plates, these can then be used to make small starters, then stepped up.

Growing yeast on slants also demands skill and sterile conditions. Germs will once again grow happily on your agar. A slant is some agar solution in a test tube. The test tube is rested on an angle, while the agar is setting, this gives a larger surface area for yeast to grow on. Yeast is innoculated onto the surface. After a week or so, there is plenty of yeast growing and any infections will be visible. It requires a good understanding of working with sterile transfers. A small amount of starter wort is added to the tube, this is allowed to ferment and then stepped up a number of times untill there is enough active yeast to pitch to a full sized brew.

Storing yeast samples in small sample jars under beer or water will not allow you to judge if the yeast is infected till you grow a starter up and taste it.

Anyone interested should hunt up Sosman's yeast wiki. This includes many links to useful sites that clearly outline the involved process of slants, sterile water storage and plates.

Remeber, every beer is infected, it just depends with what and to what degree. The only time you can say a yeast is not infected is when it has been activly growing on a plate for a week and only shows yeast colonies. Once you expose wort to the air, it will be infected.

 

[Sprungmonkey]

Thanks pint of lager - this make more sense as to why you use slants over broths (ie easy identification of contamination).

I guess the only other way to look at an innoculated broth sample to see if it is contaminated is to put a sample under a microscope. Yeast cell are quite different (and larger) than normal bacterial cells. The only trouble is wild yeast cells which are a little harder to differientate.

When tasting a starter what does a infected starter taste like in comparison to a sterile starter?

 

[pint of lager]

Broth is a soup term that is not used in brewing. You are making wort and beer, not broth.

You are storing large samples in bottles/jars/test tubes under either water or beer.

You are storing small samples on either slants or petri dishes. The agar solution also includes malt as nutrient for the yeast.

If you use petri dishes streaked correctly, the colonies are isolated, they grow as discrete dots on the agar, wherever one yeast cell has been inocculated, one dot of yeast grows. Poor streaking makes the yeast appear as lines on the agar substrate. The shape and size of the yeast colony is used as one way to distinguish a good yeast. Select uniformly shaped and sized dots, not the funny shaped, coloured or sized dot. It takes about 4-7 days to start from a few match heads of yeast from a petri dish to step up to a decent sized starter ready for pitching in a 20 litre wort.

Taste all your starters and fermenting worts. Different yeasts show different characteristics as they ferment. There is no firm taste test to say what is infected or wrong.

If you go the microscope path, you are going to need a good one, capable of 1,000x. Better to spend that money on a pressure cooker and some glassware.