Q for people who make yeast starters

[clibit]

I've never bought a Brewlab yeast but intend to at some point, and I've always wondered, after reading the preparation guide on their website, why it's ok to make up a 300ml starter with their yeasts slants. A much larger yeast starter is the norm for a full size batch, so what is the difference? Would a 300ml starter suffice if I made it up from other yeast sources? This is the method they ask you to follow:


Starter Cultures
To grow the yeast from the slope prepare a nutrient solution of malt broth by dissolving three table spoons of malt extract in 300 cm³ of boiled water in a clean sterilised flask or bottle of at least 500 cm³ size.

When cool (below 35 C) pour some of the solution onto the yeast culture and shake to suspend the yeast cells. Alternatively a flamed wire loop may be used to loosen the cells. DO NOT ATTEMPT TO DISSOLVE THE SLOPE. THE CELLS ONLY GROW ON THE SURFACE OF THE AGAR AND SHOULD BE DISLODGED BY SHAKING.

Transfer the yeast suspension into the rest of the nutrient solution and allow to grow for 24 to 48 hours in a warm environment (20-30 C) as a starter culture in your brew. Cover the bottle opening with aluminium foil or plug with cotton wool. DO NOT INCUBATE A STARTER CULTURE IN A TIGHTLY SEALED BOTTLE AS PRESSURE MAY CAUSE IT TO EXPLODE.

Ensure that the yeast is working well before pitching. It should show a frothy surface as gas is released and have a good sediment of yeast cells at the bottom. Ensure that all of these are pitched into your wort to achieve maximum speed of fermentation.

 

[Spapro]

Hi Clibit,

No idea on the science but I've used 2 brewlab slopes just recently (30g Light DME boiled in 325ml of water leaves me with approx 300ml of solution post boil) and they gone off really well - both fermenting now, both FV have a thick, creamy layer of foam present.

I have only used dried yeast in the past but these are without doubt the most rigourous 'healthy looking and sweet smelling' ferments I have had.

I have cultivated my starters for 2-3 days at 20-21°C before pitching.

Given that most dried yeast sachets are only say 12g then I guess you don't actually need that many yeast cells pitched into 23l to get things started.

 

[clibit]

Cheers Spapro. This 300ml thing just seems to go against the common practice. 12g dry yeast packets actually hold a lot of yeast cells, a lot more than a liquid yeast packet.

I think liquid yeast packs have about 100 billion cells, dry yeast has about 18 billion per gram. So an 11g pack has about 200 billion, which is about right for a 5 gallon brew. I read to day that a liquid yeast has enough cells for about 12 litres of 1050 beer.

This calculator suggests you need a 1 liter starter with 100g DME for a 23 litre brew with 1045 OG.

http://www.brewunited.com/yeast_calculator.php

 

[MyQul]

Do the yeast slants have a much higher concentration of yeast cells? I've never actually seen a yeast slant, not even a picture

 

[clibit]

I doubt it, I'd expect them to have a lot less than a White Labs or Wyeast pack.

 

[DanST]

Dried yeast is essentially "dormant" in that until you rehydrate it its not doing anything. Yeast on a slope will actually be metabolising so using sugar , nutrients, oxygen etc and growing all be it at a fairly slow rate especially if kept cold. It's common practice in labs to store yeast like this short term (months).

Because the yeast is growing but at an extremely reduced rate it will "wake up" and get going again alot quicker compared to dried yeast. When you put a tiny amount of the yeast from the slide into the starter they start growing like crazy, very quickly giving you enough cells to ferment your brew.

Dried yeast will take longer to get going and the drying and rehydration will kill a lot of cells so the amount in a pack should be quite a big excess of what is needed to make up for this.

It's not practical to maintain yeast in the fast growth phase for very long. Slides are a good way of storing yeast that can be easily made to grow rapidly again. Drying the yeast will preserve it for longer and allow it to withstand harsher conditions however more cells are damaged in the process hence the need for an excess.

Hope that's helpful. As for actual cell densities that's outside my area im afraid.

 

[clibit]

That's a great explanation Dan, thanks. But what about liquid yeasts, Wyeast and Whitelabs, people make bigger starters with those than Brewlab suggests with its slants.

 

[DanST]

There should be more cells in a liquid culture than you would get straight from a slide so you can scale the volume up more quickly. If the cell density gets too high (no. Of cells/volume) then they will run out of nutrients or oxygen. This stops growth and is generally bad for the cells.

You could scale up the 300mL starter made from a slide but you should only really need to do this in extreme circumstances- very high sg or large volume. I'd be inclined to trust them if they say a 300mL starter is enough if prepared properly.

 

[DanST]

Should also add I'm not implying liquid is better than a slide. Personally I'd be happier shipping yeast on a slide than liquid culture but that's anecdotal, again not something I've got specific experience with.

 

[clibit]

I do trust them. I just don't understand why a vial from White Labs or Wyeast needs a 1 or 2 litre starter and a Brewlabs slant only a 300ml starter. But I am more a cook than a scientist - I'm not a scientist at all, and have no idea how my son got the grades he did in Maths, Physics, Chemistry and Biology today - he didn't get it from me! :shock:

 

[ManseMasher]

Don't know about the maths or the science mate, but I used a Brewlabs Sussex 01 for a Harvey's Best clone. 300ml as the instructions stated went off like a rocket, gave me the taste I was looking for and as a bonus has fed my next two brews. All I can think is, living yeast is far more effective than dried, the agar slope is a really healthy hoste, and if started correctly, is damn near foolproof!!

I've never bought a Brewlab yeast but intend to at some point, and I've always wondering, after reading the preparation guide on their website, why it's ok to make up a 300ml starter with their yeasts slants. A much larger yeasts starter is the norm for a full size batch, so what is the difference? Would a 300ml starter suffice if I made it up from other yeast sources? this is the methoid they ask you to follow:


Starter Cultures
To grow the yeast from the slope prepare a nutrient solution of malt broth by dissolving three table spoons of malt extract in 300 cm³ of boiled water in a clean sterilised flask or bottle of at least 500 cm³ size.

When cool (below 35 C) pour some of the solution onto the yeast culture and shake to suspend the yeast cells. Alternatively a flamed wire loop may be used to loosen the cells. DO NOT ATTEMPT TO DISSOLVE THE SLOPE. THE CELLS ONLY GROW ON THE SURFACE OF THE AGAR AND SHOULD BE DISLODGED BY SHAKING.

Transfer the yeast suspension into the rest of the nutrient solution and allow to grow for 24 to 48 hours in a warm environment (20-30 C) as a starter culture in your brew. Cover the bottle opening with aluminium foil or plug with cotton wool. DO NOT INCUBATE A STARTER CULTURE IN A TIGHTLY SEALED BOTTLE AS PRESSURE MAY CAUSE IT TO EXPLODE.

Ensure that the yeast is working well before pitching. It should show a frothy surface as gas is released and have a good sediment of yeast cells at the bottom. Ensure that all of these are pitched into your wort to achieve maximum speed of fermentation.

 

[clibit]

I've been interested in the Brewlab slants for ages but never got round to buying one. I must. Thanks for the info fellas. It sounds like a nice simple process, and I like the idea of talking to them to identify suitable yeasts.

 

[DanST]

It will be to do with providing enough volume to get the yeast growing well. Your better off pitching a low number of cells that are growing quickly than loads of cells which have run out of nutrients and have basically gone to sleep as a result. They'll get going again eventually but it will take a while for them to wake up.

The 2 methods of supplying the yeast are slightly different so the starter culture methods will be optimised for each.

 

[HebridesRob]

A few years ago I used to culture yeast from the bottom of a bottles of Guinness (there was some there in those days) and Worthington White Shield to pitch into homebrew.

Not sure this post is directly answering your question but here's some science on yeast growth. The bit in bold might explain a little.

From here:
http://www.braukaiser.com/wiki/index.php?title=How_pH_affects_brewing

Shortly after being pitched into fresh wort yeast will start lowering the pH of the surrounding medium (i.e. beer). This is the result of ammonium ion and amino acid uptake, secretion of organic acids [Briggs, 2004] and most importantly a proton pump which moves H+ ions from the yeast cell into the beer. By doing so the yeast also raises its internal pH. This proton pump is very important to the yeast and it is the most abundant protein in its cell membrane [Briggs, 2004]. The resulting pH gradient through the yeast's cell wall facilitates the uptake of nutrients like maltose.
Maltose uptake is a proton symport process through the cell membrane. The proton concentration outside the cell is greater (lower pH) than inside the cell (higher pH) and therefore a natural gradient exists which encourages protons to flow from the outside to the inside of the cell. Though the use of a symporter, a cell membrane protein, maltose can “piggy back” on the flow of protons into the cell. This is one of the reasons why yeast cells do better in an acidic environment and have means of lowering the pH.
The ability of yeast to lower the beer’s pH is important for healthy and low yeast stress fermentation and is one of the reasons why sufficient pitching rates are important and why it is better to step up starters rather than starting a small amount of yeast in a large starter. The more yeast cells that are working on lowering the pH the faster the pH will be able to drop.
As yeasts age, starve or otherwise loose their vitality, it becomes increasingly difficult for them to pump H+ from their cells into the beer. After all, this goes against nature’s desire to equalize everything and therefore takes energy. The result is a slight rise of the beer pH after primary fermentation. The pH can rise more significantly if the beer is not taken off the yeast before a large number of yeast cells start to autolyze."

 

[clibit]

It will be to do with providing enough volume to get the yeast growing well. Your better off pitching a low number of cells that are growing quickly than loads of cells which have run out of nutrients and have basically gone to sleep as a result. They'll get going again eventually but it will take a while for them to wake up.

The 2 methods of supplying the yeast are slightly different so the starter culture methods will be optimised for each.

Yes that is very clear and makes perfect sense, thanks. Think I'm getting there!

And I think Rob's article backs it up, in the bit that talks about the vitality of the yeast being important. It's quality v quantity I guess.

 

[Spapro]

I've been interested in the Brewlab slants for ages but never got round to buying one. I must. Thanks for the info fellas. It sounds like a nice simple process, and I like the idea of talking to them to identify suitable yeasts.

Brewlabs have added an extra box on their Yeast purchase web pages, so you can enter a specific number for a yeast after you have spoken to them about what you are looking for and they give you a reference number.

I will post a picture of one of my yeast slopes - its effectively a small plastic test tube with a screw lid with a wax like 'glob' allowed to dry on a slant - hence the term slope. The yeast cells are sitting on the slope in a snot like dried layer.

You 'wash' the yeast off the slope by popping a small amount of your starter wort into the test tube, scew the lid back on and shake the test tube to lift the yeast off the slope and then pour that into the rest of your 300ml starter.

At £6 a slope I am skimming a couple of days into the fermentation to harvest some yeast for future brews - will probably get 3 brews out of each slope I think.

I would say that Brewlabs seem like more of a Lab operation than a slick online retailer outfit. My first order didn't get dispatched aand when I called to chase they then quickly sorted and dispatched. You may need to check/chase your order but the end result I think is worth it.

 

[clibit]

Thanks Spapro. They seem to gave caught up on price with the liquid yeasts, used to be a bit cheaper. But they are in the UK and offer a personalised service and the yeast is fresh.

 

[Spapro]

Thanks Spapro. They seem to gave caught up on price with the liquid yeasts, used to be a bit cheaper. But they are in the UK and offer a personalised service and the yeast is fresh.

I know what you mean. In one of my books, not sure if its Hughes or Wheeler, they make the point that liquid yeasts have often been shipped round the world in all sorts of storage/shipping conditions. The Brewlab slopes are prepared to order so can't get much fresher.

Think they last for 6 months if stored in the fridge, I have a few in my fridge for brews through the Autumn.

 

[duncans]

I agree 300ml starter sounds like a massive under-pitch compared to the white labs and wyeast norms.

I have been splitting white labs and wyeast packs, using a portion on brew day then splitting the rest into 5/6 lots of about 5 bill cells ish and storing them in glycerin/water in the freezer until i need them. I make 250ml @ 1040 starters with yeast nutrient to grow them up and get a healthy culture going and pitching this. So far so good, but I've only done a few 5l brews with it as yet and not had chance to re-use the yeast in a second brew to see how it stands up to this.

The theory is sound though, in my limited opinion. The first 24 - 48 hours in the brew is the lag phase and the yeast goes through exponential growth, doubling every 4 hours, so as long as there is oxygen and nutrients to help things along and no competing organisms then it should reach the natural cell count even with a massive under-pitch. I think people are against under-pitch because they worry about off-flavours from poor yeast growth, and the possibility of other yeast/ bacteria getting in. I think you can reduce the risk of these in other ways.

If we listen to all the stuff that gets talked about , about yeast , we could be forgiven for beleiving no-one ever made good beer before wyeast/white labs put a yeast pitching rate calculator on their website! And that yeast hadn't been growing perfectly well on its own for last few billion years or so.[emoji4]