dry yeast

I have been using dry yeast the likes of saflager 34/70, what I nwould like to know is can I rehydrate and then use some dry malt to make a starter

It's recommended to rehydrate before use but not to make a starter. the yeast sachets come with loads of nutrients and food for the yeasts in, but don't remember why that's bad for a starter. When I've needed a higher cell count than one pack I've changed my brew schedule slightly so I ferment a lower OG beer first then use the yeast from that batch in a higher gravity beer.

by making a lower og beer, the same as making a starter ?

Heres the manufacturers instructions http://www.murphyandson.co.uk/Datasheets/Yeast - Saflager W-3470 Yeast.pdf note according to there dosage instructions you need 2 packs for a 23L/5 gallon batch. Heres a discussion on it you may find useful https://club.coopers.com.au/coopers-forum/topic/15488/

I've never heard of it being a bad idea, nor of dry yeasts being loaded with "nutrients and food" - there just isn't enough room in the packet, especially if 96%+ is yeast cells!

If you don't have two packets for a high S.G. beer at least a mini-starter is a good idea and I have done it a lot of times.

thanks for your input and the threads

There is a good reason for using only water as a starter with dried yeast. Because the yeast has been dehydrated you are effectively waking it up and it rapidly absorbs liquid as it comes alive unfortunately it absorbs everything and sugars in any form can cause stress at this stage which can detrimental to the yeast and beer. Liquid yeast is the opposite and benefits if you can let it "get to know" the wort it is going to service.

TheQuokka said:

I've never heard of it being a bad idea, nor of dry yeasts being loaded with "nutrients and food" - there just isn't enough room in the packet, especially if 96%+ is yeast cells!

If you don't have two packets for a high S.G. beer at least a mini-starter is a good idea and I have done it a lot of times.

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Just because you haven't heard it doesn't mean it isn't true. Jceg and trueblue are quite right, just rehydrate with tap water otherwise you'll do more harm than good.

Not sure if I agree with all this. Although you don't need to make a starter from dry yeast, it won't be any less healthy than a starter made from liquid yeast. If it is a high gravity lager you are making and you only have one pack of 34/70, then I would rather make a large starter to get to the right pitching rate than underpitch dry yeast. This is what I did for my Dogma clone, and worked really well.

Yes, certain comments are again a bit strange and fly in the face of the experts and popular experience. If all this mysterious bad stuff was going to happen to the dried yeast in a starter, it would occur when pitched into a full volume.

Llalemande have a blog where their scientists answer questions like this and while it is long and perhaps overly in-depth, it does dispel such myths.

IainM said:

Not sure if I agree with all this. Although you don't need to make a starter from dry yeast, it won't be any less healthy than a starter made from liquid yeast. If it is a high gravity lager you are making and you only have one pack of 34/70, then I would rather make a large starter to get to the right pitching rate than underpitch dry yeast. This is what I did for my Dogma clone, and worked really well.

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You can make a starter with dry yeast to increase cell count, however it is best practise to rehydrate the yeast in water before you add it to the starter wort. @trueblue give the reason why dry and liquid yeasts are different, the membrane of dehydrated yeast cells are not selective during the "waking up" process which can cause osmotic stress in the cell as it absorbs sugars and minerals from wort.

TheQuokka said:

If all this mysterious bad stuff was going to happen to the dried yeast in a starter, it would occur when pitched into a full volume.

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You're right, and it does. In the "Yeast" book by J Zainasheff and C White (of White Labs Yeast) it's stated that pitching dry yeast directly into wort can kill up to half of the cells.

TheQuokka said:

Llalemande have a blog where their scientists answer questions like this and while it is long and perhaps overly in-depth, it does dispel such myths.

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Quote directly from Lallemand: The media used is crucial to a successful rehydration. Undiluted wort causes osmotic pressure to the yeast and compromises its health. Most yeast strains can be rehydrated in water but lager yeasts benefit from rehydration with a small concentration of sugar, so diluted wort (3° Plato) is preferred.

I wondered where the myth of half the cells dying from dry pitching came from and am not surprised it comes from someone who sells an overpriced "liquid" yeast product...

You should read a little more from Lallemand, not just pick out the bits that seem to support your beliefs.

I'm certainly no expert, so for my "beliefs" I have to listen to what the actual experts tell us. So what is the basis for your claim that it it is a myth, presumably you have some evidence and it's not simply your belief?

TheQuokka said:

I wondered where the myth of half the cells dying from dry pitching came from and am not surprised it comes from someone who sells an overpriced "liquid" yeast product...

You should read a little more from Lallemand, not just pick out the bits that seem to support your beliefs.

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I don't mean to be argumentative Quokka, but an opinion based on some unsubstantiated liquid yeast company conspiracy theory doesn't really add much to the conversation. Especially if it contradicts a large body of evidence.

The idea of osmolarity being detrimental to yeast health was first shown in a paper by Laroche and Gervaise, which they have kindly made available to download free from ResearchGate. Their paper is highly cited and the experiment has been repeated many times, including in this relevant paper which, you might be surprised to find out, was performed and funded by Lallemand Inc, as well as other papers such as this one, which investigates the downstream consequences for beer due to osmotic pressure dependant loss of cell viability during rehydration (spoiler: low viability means longer ferment times and more diacetyl, amongst other things).

If technical details don't do it for you, then this blog post should be more accessible. The writer rehydrates one packet of yeast in three media: water, starter wort and high-gravity wort. He then uses a microscope and counts the number of dead yeast and live yeast, and works out the viability from the ratio of these two numbers. The results are pretty clear, and consistent with the science.

Anyway, back to the original question. Yes, you can make a starter from dry yeast to build up the cell count, but rehydrate it first.

TheQuokka said:

I wondered where the myth of half the cells dying from dry pitching came from and am not surprised it comes from someone who sells an overpriced "liquid" yeast product...

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The yeast book is by far the most definitive book on the subject I have come across because it explains yeast in a way most of us can understand rather than some of the pieces designed for more scientific minds than mine, even if I had to read the book twice. It is a long way from being an "advert" for their products quite the opposite as they tell you how to use each vial several times, how to create your own yeast lab as well as harvesting from bottles etc. hardly the way to sell more yeast. You don't start and run a highly regarded yeast lab without knowing what you are talking about. I explain in this thread
http://www.thehomebrewforum.co.uk/showthread.php?t=70067 how I've not bought yeast for over a year, and I brew every two weeks, so sorry but the overpriced tag is just wrong. I can never fathom why someone will pay out for ingredients, spend 4-5 hours brewing then when it comes to the most important ingredient add an inferior product in the belief they are saving a few pence. If you are brewing to save money just brew kits. If you haven't read the book please read it. Understanding yeast rather than opening a packet is the best way to improve your beer and maybe take on to the next level.