Why don't stir plates introduce infections ?

[bobukbrewer]

Airborne bacteria will attack the sugar solution surely ? And if you introduce an inert atmosphere, how can the stir plate work ?

 

[strange-steve]

The top of the flask is loosely covered with foil so airborne bacteria doesn't get in. Also you're pitching a huge amount of yeast in comparison to the wort so there's little chance of bacteria getting a foothold.

 

[foxbat]

Exactly what @strange-steve says. Bacteria don't have legs and can't crawl up under the foil and that which is in the air gets out-competed by the huge number of yeast cells that you introduce. Same rules as for your main fermentation, just on a smaller scale.

 

[MyQul]

Exactly what @strange-steve says. Bacteria don't have legs and can't crawl up under the foil

You ain't seen Gunge's bog!!

 

[cushyno]

You ain't seen Gunge's bog!!

What's he doing with foil over his bog? That's some evil substitute for an Erlenmeyer Flask!

 

[Bigcol49]

What's he doing with foil over his bog?

To protect the grain during sparging

 

[Dutto]

Please check this video out. The presenter isn't being OTT with his sanitation, just very careful!

 

[bobukbrewer]

BUT - the foil in effect stops air contacting the starter and so the yeast cannot multiply rapidly, and if you say some air gets in then so do some bacteria - they are ever present in air. I think mixing the yeast with the 4:1 waterME and leaving it at 25 deg C in the dark, unagitated, will achieve the same result without the risk of infection. My own starters are 100 ml cooled boiled water, 1 teaspoon of brewing sugar and 1 sachet of Safale 04 yeast. This is in a 1 pint jug which is clingfilmed. I get a 2 inch solid head on the starter in about 2 hours, when I pitch it. Thirty years, about 1100 brews, no failures yet.

 

[Cwrw666]

What's he doing with foil over his bog?

It works better if you stretch clingfilm over your bog rather than tinfoil.

 

[strange-steve]

The foil is loose to allow CO2 to escape and air to enter and yes, any air which enters will have some bacteria, but nowhere near enough to cause a problem. In a starter the pitch rate is probably 5 times as high as a typical pitch rate for the full batch, which in itself is enough to discourage infection. There's lots of research which shows that constant agitation greatly increases cell growth in comparison to no agitation, which is really the point of the starter.

 

[Sadfield]

Sure, there will be airborne bacteria in your starter, but it will be vastly out numbered by the billions of yeast cells pitched into it from a packet of yeast. Those cells will multiply until the environment is made too hostile for them to survive, by the yeast. Same when you pitch that yeast into the fv, there will be bacteria in your fv, wort (and Starter), due to the fv being sanitised, not sterilised. The healthy pitch of yeast soon kicks in lowering the wort pH and producing alcohol to kill off most bacteria.

 

[BeerCat]

I have stored wort in flaks for months without any problem. Covered with foil, cling film and a band.

 

[Bigcol49]

I have stored wort in flaks for months . . .

 

[BeerCat]

View attachment 17894

Ah Colin another spelling mistake. I meant to say my kaks!

 

[AdeDunn]

View attachment 17894

That'll agitate the yeast, I'll bet!

 

[Bigcol49]

That'll agitate the yeast, I'll bet!

Definitely create a stir!