Renewing The Yeast Cultures

[Zwickel]

I notice in your post that you had the wort on a stirrer and ALSO were adding aeration. Have you found the added aeration to make a significant difference?
I get very good growth just on the stirrer, but was wondering whether adding extra air is worth the contamination potential.

it depends on the time I have and what kind of beer Im gonna brew.
Of course, there is a significant difference in growth.
Just from feeling I would say that the yeast will grow 5 to 10 times faster if the starter gets additional airated.

For Pilseners you cant get a starter big enough for 60l of wort by stirring only, within one week. As you may have seen in my pictures, I need at least 500ml stiff yeast.
Thats completely different if you are using top fermenting yeasts, such as for an Ale or Hefe Weizen. For that, stirring only would be far enough.



Cheers

btw. I never had any infection

 

[kabooby]

Thanks Zwickel, Makes sense

Kabooby :icon_cheers:

 

[andreic]

This is an interesting thread. I'm thinking of giving the slants a go. One question though...

How long do the slants last in the fridge?

Some of the links posted in this thread suggest 3 months! Then you have to "renew" the yeast. But some of the posts in the thread suggest up to a year!

Up until now I've been storing my liquid yeasts in stubbies after growing a starter from the original whitelabs tube or wyeast pack. This takes up a lot of room. I also reckon some of my older yeasts were not quite in "optimum" state when revived. My last hefe, whilst ok, lacked somewhat in the aroma and flavour department when compared to the previous beer prepared exactly the same way. I'm looking at slants as a way to keep yeast in better condition for longer... but how long?

cheers

 

[Hogan]

Zwickle, try adding a bit less agar/malt solution to the tubes and laying them down a bit further. This will give a greater surface area for the yeasties to do their thing.

Had some deep and meaningful discussions on yeast culturing yesterday with Franko and Kabooby. (The more pubs we attended the more D & M it became). Discussed slants and what we would use to grow the yeast in - tubes etc. After clearing my head this morning I considered that the reason the tubes are slanted was to get as large a surface area for the yeast cells to cling to the agar. I found a small jar which had apparently been used for jam. Its volume is 30ml and it stands 4cm high with a screw top metal lid. These would give a much larger surface area than a tube and could be sterilised as effectively. I have attached a pic. Have looked at a number of sites for jars and Lab equipment but none seem to have this size. Any ideas where I might be able to procure them. They appear to be a type that may be used on airlines or for samples of food etc. Any suggestions would be appreciated.

Cheers, Hoges.

 

[Duff]

Agar is also cooled on a slope in laboratory uses so that any moisture also collects at the lowest point and not on the agar itself. If agar is mixed with any bacterial inhibitor and moisture gets on the surface, the inhibitor is diluted and contamination occurs.

Same principle for your yeast slants, less moisture, less contamination on the surface of your agar.

 

[Zwickel]

How long do the slants last in the fridge?

gday mates,

the professionals suggest not to exceed 3 month. Thats for professional brewing like in the industry.

I have used and successfully revived slants even after 2 years. I cant say anything about the quality of that yeasts, but I can say that the beer was made from didnt showed any flaws.

@Hogan, of course you may use any type of glass that hermetically can be closed. At my start on yeast farming Iv used mainly glasses where baby food had been in. It worked well all the time. Only, because my yeast collection became larger, I had to switch to smaller vessels.

@Duff, what you said is right, its recommended to keep the agar as dry as possible. Never put in a drop of liqid yeast for inocculation. That would be far too much moisture. Just roll a cotton wool swap over the surface, thats enough.

In case youd get too much moisture in your vessel, the yeast may get under the agar and its CO2 production leaves the agar floating.

Cheers :icon_cheers:

 

[kabooby]

In case youd get too much moisture in your vessel, the yeast may get under the agar and its CO2 production leaves the agar floating.

I have had this happened now to one of my slants. I haven't used them yet so I am assuming they will still be ok.

Kabooby

 

[Zwickel]

I have had this happened now to one of my slants. I haven't used them yet so I am assuming they will still be ok.

Kabooby

yeah, when I started to work with agar, I was always concerned to get too less yeast in, so I put in far too much yeast and moisture. All of my agars started floating in the glasses. That time I didnt know why the agar got a lift up, only later I realised, that its the Co2 that gives it a lift.

Anyway, as long as you dont get any strange germs in, it doesnt matter, it just doesnt look nice. I never had any infected agar.

Cheers :icon_cheers:

 

[Leigh]

Thanks very much, I have 2l and 3l erlenmeyer flasks and have trouble keeping the stir bar centred even though they are flat bottomed when there is a large yeast load. I was thinking of using a 5l bottle like yours but thought I would have trouble keeping the bar centred because of the domed base.

From my lab days, the size of the magnet in the magnetic stirrer, the size of the stir bar, the speed of the stirrer and the viscosity of the solution all affect the stability of the stir bar...if you are not getting the stir bar to centre, try a smaller stir bar and/or start stirring slow and gradually increae the speed...even then, sometimes you can not get up to the maximum speed of the stirrer.

Flat bottom glassware assisted the stability...round bottom flasks needed quite small stir bars to stay stirring centrally.

 

[Sprungmonkey]

These are my first slants

 

[kabooby]

Look good Sprungmonkey :icon_cheers:

 

[alexbrand]

These are my first slants

Reminds me of a urine test... *g*

Just kidding, looks great. How did you prepare the slants?
To prevent infections I got used to put the whole filled tubes at the end into a pressure cooker for some minutes. So i don't have to work that clean in all the different steps before. Saves time and protects my nerves. If the tubes are deliverd sterile there's no need to do so...

Greetings,

Alex

 

[Sprungmonkey]

Reminds me of a urine test... *g*

Just kidding, looks great. How did you prepare the slants?
To prevent infections I got used to put the whole filled tubes at the end into a pressure cooker for some minutes. So i don't have to work that clean in all the different steps before. Saves time and protects my nerves. If the tubes are deliverd sterile there's no need to do so...

Greetings,

Alex

Made up media (wort and agar agar) in a 1L Schott bottle, Autoclaved (15mins @ 121C), poured into centrifuge tubes and let set. Luckly I have access to an autoclave.

Cheers
Dave

 

[Hogan]

These are my first slants

These are the same size Franko was thinking of getting. 50ml is a good size and there seems to be plenty of surface area on the slant. Thanks for the pic Dave.


Cheers, Hoges.

 

[Sprungmonkey]

One other thing. I always have a flame and metho handy for sterilising inoculating loop and after opening jars etc. It just good practise to quickly flame lids and lips of containers when pouring transfering etc.

Just thought I would add that.

 

[maltedhopalong]

I have a little question...

Will a yeast keep better (healthier, more viable cells etc.) in a slant or in pure water in the fridge?

The reason I ask is that it would take less space/time/money to just keep one jar of yeast in the fridge in pure water and when you create the starter, you make one bigger than you need, pitch half and then dilute the other half with pure water and put it back in your original jar...

Suppose there's a good reason why this won't work tho

 

[alexbrand]

Made up media (wort and agar agar) in a 1L Schott bottle, Autoclaved (15mins @ 121C), poured into centrifuge tubes and let set. Luckly I have access to an autoclave.

Your're really lucky! But... aren't those sample tubes autoclavable? So I would sterilize theready made tubes. This is even more secure and consumes the same time, I think?

Will a yeast keep better (healthier, more viable cells etc.) in a slant or in pure water in the fridge?

On a slant! In pure water the yeast suffers from famine. On a slant the cell will find food in the begining. The cell consumes it and propagates. But soon it'll "fall asleep" as long as no nutrients are available. If you "start" the slant later with frsh worth. The cells wake up and get busy...

Greetings,

Alex

 

[maltedhopalong]

the yeast suffers from famine

Suffers how? Does it die or just go to sleep? Considering the effort you go to to make a starter from an agar slant, I'm thinking if it only goes to sleep, it's easier to just keep a jar of washed yeast in the fridge and pitch the whole jar to start a new brew. Then collect the trub, wash and keep THAT in the fridge. Less (or same) work, less cost and presuming you don't need to do two brews with the same yeast at the same time, endless supply.

Sorry to hijack the thread with more low-level questions.

 

[Zwickel]

maltedhopalong, the answer of your question Ive given already in post#41 in this thread.

in a liqid the yeast will start to degenerate and suffers from autolysis.
Later, if youre going to do a starter from that kind of yeast, youll get all that **** into your brew.

Beside, one cannot wash the yeast to separate the dead cells from living ones, they are at the same size and weight.

Cheers :icon_cheers:


P.S. if youre going to brew fortnightly, then it would be fine to keep the yeast just in the fridge. On agar its more a long term storing method.

 

[maltedhopalong]

cheers Zwickel, sorry mate.

I did read your post but obviously didn't understand it 100% as I've never done a slant myself (specifically about how washing doesn't have the same effect).

Like I said, sorry about the noob angle, but appreciate your humouring me anyway.