Yeast starter queries

[guypettigrew]

Never having made a yeast starter before, I'm now giving it serious thought. But there's a few things I don't understand. Advice would be welcome.

Boiling the malt extract in water for 10-15 minutes is recommended. Why is this? Wouldn't dissolving the DME in boiling water from a kettle also ensure a sterile solution?

Shaking the solution vigorously (before and after adding the yeast) to incorporate oxygen is recommended. But doesn't this hugely increase the risk of infection getting into the starter?

Finally, I think I've read somewhere on JBK that it's not a good idea to make a starter up if you're using dried yeast. Can't remember why.

Thanks in advance for your replies.

Guy

[orlando]

Never having made a yeast starter before, I'm now giving it serious thought. But there's a few things I don't understand. Advice would be welcome.
Boiling the malt extract in water for 10-15 minutes is recommended. Why is this? Wouldn't dissolving the DME in boiling water from a kettle also ensure a sterile solution?

Not worth the risk, your yeast is in a very vulnerable situation at the beginning of a starter, often due to manufacturing date it is already losing cells rapidly. 10 minutes should be plenty.

Shaking the solution vigorously (before and after adding the yeast) to incorporate oxygen is recommended. But doesn't this hugely increase the risk of infection getting into the starter?

If the flask you are putting the solution is sterile (sterile note not just sanitised) and covered then there is little chance of that being a problem.

Finally, I think I've read somewhere on JBK that it's not a good idea to make a starter up if you're using dried yeast. Can't remember why.

Dried yeast is designed to be self sufficient during rehydration so oxygenating is not required.

[guypettigrew]

Thanks Orlando. Makes sense, apart from one little thing.

If the flask is covered, then surely the only oxygen able to get into the starter is that which is in the headspace of the flask. Unless the cover is taken off during the shaking.

Or am I worrying unnecessarily? Will there be sufficient oxygen in the headspace of (say) a 1 litre flask when making 1 litre of starter to get the yeast going?

Thanks again.

Guy

[orlando]

There is some interesting experiments to suggest that very little oxygen is needed anyway, that all that needs to happen with a starter is that yeast cells are kept in suspension. Look up Crabtree effect. Personally I use a foam stopper, King Scientific carry them after I asked them to stock them in their Home Brew section. The theory here is that they are porous enough for gaseous exchange but will keep out bacteria. Bottom line: yes you are worrying unnecessarily.

The key to success with yeast "ranching" is sterility, at our level this is best approached by using a pressure cooker to sterilise whatever the yeast comes into contact. You can "get away" with a lot of things in brewing but attention to this detail with yeast is, in my view, not one I think you should be taking risks with. If you end up making and using slants it becomes even more important. Unfortunately if you are going to use flasks up to 2l in size you're going to need a big one and they are rarely found outside the States. I had a thread on here about how to set up for all this that might still be available, think it even had some links too, but basically it was a search on the US Ebay site, from memory my PC cost circa £80 and frankly is a bargain as I use it for sterilising my plate chiller as well as flasks and making wort starters in Kilner jars so I have a steady supply ready to go. I use it as much as the rest of my kit. If you need to justify it to the opposition I understand you can even use it for food!

[rpt]

Boiling water doesn't instantly kill all bugs. Boiling for 15 minutes doesn't either but it should kill enough for a starter provided there is enough viable yeast.

[Waffty]

Boiling water doesn't instantly kill all bugs. Boiling for 15 minutes doesn't either but it should kill enough for a starter provided there is enough viable yeast.

I believe that boiling water in a pressure cooker, with the full 'weight" on the pressure regulator, raises the water temparature to around 120C, which on a 30 minute boil, should be enough to kill most things and certainly acceptable for home brewing.

Most pressure cookers have a cooking (operating) pressure setting between 0.8 - 1 bar (11.6 - 15 psi) above sea level pressure (sea level pressure is around 1.016 bar) so the pressure cooker operates at 1.816 to 2.016 bar. The standard cooking pressure of 15 psi above sea level pressure was determined by the United States Department of Agriculture in 1917. At this pressure, water boils at 121 °C (250 °F) (described in vapour pressure of water article).

Since I bought my pressure cooker, I haven't looked back. It isn't big enough to put in a 2l flask but I can get 2x1l kilner jars in there, which I fill with wort and leave the lids loose'ish. I then put the 2l flask in the oven with a slight amount of water in the bottom and tin foil around the opening. I then cook it at 140C for 30mins.

Wait to cool, pour in the wort, with a gas hob burner on, pop in the sterile foam stopper, wait for it to cool to pitching temparature, give it a swirl and bish bosh, job done.

[rpt]

Boiling in a pressure cooker will sterilise. I was referring to boiling at sea level.

[guypettigrew]

Not having a pressure cooker, the idea of sterilising the flask in the oven at 140C for while appeals greatly.

My latest brew took 48 hours to show any sign of fermentation starting. Although it's in a SS Brewing Technologies chronical, with the lid firmly clamped down, this is still plenty of time for the wort to incubate lots of horrid things. The yeast is White Labs 007 collected from a previous brew on 21st November 2015 and stored in the bottom of the 'fridge since then. I reckon it either went very dormant or quite a lot dead!

Hence my sudden interest in yeast starters. I don't want this much down time again. Also, this current brew fermented really strongly (once it got going!) for about 36 hours and has now stopped. I haven't checked the SG, but it seems unlikely it's reached 1/4 gravity already. Possibly a failed brew.

A 1 litre Erlenmayer flask is on its way to me. I'll be trying a yeast starter for the next brew.

EDIT; just checked the SG. It's dropped from 1.052 to 1.040 and stopped. Smells a bit off as well. The only brews I've ever thrown away have been ones where the fermentation took ages to start. This one looks like it'll be going down the drain.

Guy

[orlando]

Not having a pressure cooker, the idea of sterilising the flask in the oven at 140C for while appeals greatly.

Er, you might want to check this first.

[guypettigrew]

Not having a pressure cooker, the idea of sterilising the flask in the oven at 140C for while appeals greatly.

Er you might want to check thisfirst.

Oh blimey! This is difficult. Vaguely remember about Tyndallisation from my science studies many years ago. Perhaps I should stay with dried yeast. A couple of weeks ago I went to a local microbrewery on the day they were brewing. Their yeast? Ten sachets of Safale US-05 for 1Bbl of brew.

My last brew is definitely going down the drain. The 007 yeast must have been too far gone to be used.

Guy

[Pegasus]

Not having a pressure cooker, the idea of sterilising the flask in the oven at 140C for while appeals greatly.

Er, you might want to check this first.

You also need to check this too. In labs we used dry heat at 160C for 2+ hrs (depending on load). I do my glassware at 180C in fan oven for 45-60 mins (with whatever's being cooked). Never had sterility issues.

[orlando]

Not having a pressure cooker, the idea of sterilising the flask in the oven at 140C for while appeals greatly.

Er you might want to check thisfirst.

Oh blimey! This is difficult. Vaguely remember about Tyndallisation from my science studies many years ago. Perhaps I should stay with dried yeast. A couple of weeks ago I went to a local microbrewery on the day they were brewing. Their yeast? Ten sachets of Safale US-05 for 1Bbl of brew.

My last brew is definitely going down the drain. The 007 yeast must have been too far gone to be used.

Guy

Get a PC, mine paid for itself in a dozen brews.

[Goulders]

I use a pressure cooker to make slants, but can't fit a 1l flask in there. If you boil the starter wort (as I do) in the flask for 15 mins or so, that's sufficient and I've never had any issues (yet).

[rpt]

I doubt that many homebrewers who make starters actually sterilise the flask. I've never had a problem with Starsan.

[orlando]

If you want one that accommodates a 2 litre flask try here. A shade over £50 + shipping, don't know how much that would be but I would bet not a great deal more of you have it surface shipped.