Increasing Yeast Numbers

[geoffclifton]

I know there are technical volumes on yeast but can anyone give me a simple answer please.

I've been reading a few posts which question the ability of a packet of yeast to consume a certain quantity of fermentables. If I 'grow' a yeast on say 200mL of water and 50g of malt am I increasing the yeast population prior to pitching into a wort or am I using up some of the potential of the yeast?

A few days ago I contemplated a 45 litre batch but had one sachet of US52 and hence the above query as to wether I could have grown it up for a double batch. I just did a 28 litre on that one with an extra can of malt.

Cheers, Geoff.

[breadnbutter]

Firstly, individual yeast don't live that long but as a population they go through generations. As long as you're removing waste and replenishing food, the yeast poulation will continue to go through a number of generations. I say "a number" because it's generally accepted that dehydrated yeast (eg safale or kit yeast) are not able to sustain as many generations as liquid yeast (eg Wyeast).

So, bulking up your fresh packet of dehydrated yeast will increase yeast numbers and help you get through a larger ferment. Equally you should do this for a higher gravity ferment.

BUT, dehydrated yeast shouuld not (ideally) be put in to a sugar solution as it can shock them. They should be rehydrated for 15-20 min in a cup of pre-boiled water at ~30C first.

ALSO, 50g malt in 200ml water is too much. That is an SG of ~1.100! For batching up yeast you should aim for ~1.040, which is ~100g/L.

Volume is also important. For say 45L ou would want at least 2L.

Sterile water is also important. You can simply pre-boil your water, allow it to cool in a covered pot.

Finally, you should have an airlock in the batch fermenter. You can buy conical rubber bungs with holes drilled into them which fit a 2L soft drink bottle from many (not all) homebrew shops.

Once you've assembled all this, leave the yeast to ferment at room temp for ~2 days. You will likely see foam forming at the top by this time and it is then ready to pitch directly into the wort. Simply adjust your wort volume to account for the 2L yeast (ie for 45L make your wort up to 43L and then add the yeast).

Cheers

[geoffclifton]

Thanks very much B&B.

SO to confirm-

Sachet into a cup of water for 15 minutes then in malt water @ 100g/L for 2 days.

1 litre per standard 23 litre batch.

How would canned liquid malt compare to ldme? 100g dry is equivilant to ?g of liquid. I getting a bit over boiling ldme for ever until it dissolves properly.

Cheers, Geoff.

[OldBugman]

dry to liquid is about 1.3:1 from memory

[breadnbutter]

That looks ok. 1L should be fine for a standard brew although there's no harm in using 2L, except perhaps if the yeast doesn't settle that well (which shouldn't be a problem with packet yeast). 2 days should be adequate but a better measure is to keep an eye out for the "head" forming on top. Make sure you do sterilise everything and use an airlock.

I thought the liquid malt was 1.5x dry, eg Coopers 1.5L ~ 1kg dry. The problem here is that with liquid you generally buy a larger amount and it's harder to measure aliquots. Dry malt extract should dissolve easily in pre-boiled water, as long as you stir it in. The pre-boiled is useful because you get rid of any chlorine in the water, which does affect beer taste and can also affect the ferment, as yeast don't like too much. Unfortunately most (all?) states add chloramine to the water nowadays, which is much more stable and harder to remove, whether by boiling or filtering. Still, that's not your main concern.

Cheers

[chris.]

Thanks very much B&B.

SO to confirm-

Sachet into a cup of water for 15 minutes then in malt water @ 100g/L for 2 days.

1 litre per standard 23 litre batch.

How would canned liquid malt compare to ldme? 100g dry is equivilant to ?g of liquid. I getting a bit over boiling ldme for ever until it dissolves properly.

Cheers, Geoff.

You won't get much yeast growth in 1L. Too small.

FWIW I wouldn't make a starter out of dry yeast. Just buy 2 packets.

Geoff, here's a handy link for calculating pitching rates
http://www.mrmalty.com/calc/calc.html

[Ash]

I've taken to using the 11.5gm Saf yeasts or two 7gm kit yeasts.

I've only managed to screw up culturing so I don't even bother rehydrating anymore, I just pop it on dry.