Starter myths

I had and interesting discussion with my friend microbiologist, and he told me some interestingng things about yeast, that contradict some "common wisdom" about starters, for this post I will call them myths:

Myth no 1: Big Vortex

No, in fact you shouldn't stir the starter too strong. If you make big whirlpool, all the particles of the liquid stay in fixed positions, and there is almost no stirring action in the volume - as if there was no stirring at all.
Besides, big velocity makes damage to the yeast.
It is best to stir slowly, this way you get better air exchange and yeast health. Just a small dimple on the surface, that's perfect.

Myth no 2: Big Volumes

There is no need to step up starter to large volumes. You may as well grow yeast in comparatively small flask, but you must provide yeast with fresh nutriets: as they ferment out, you can decant the spent wort and add fresh wort on top of the yeast, and they will keep on multiplying.

Myth no 3: Aluminium foil

Aluminium foil is not the best medium to cover the flask, the air exchange is not sufficient. Microbiologists prefer to use a tight cork made of coiled sterile cotton-wool


What dou you think? True or false?

Piotr said:

Myth no 2: Big Volumes

There is no need to step up starter to large volumes. You may as well grow yeast in comparatively small flask, but you must provide yeast with fresh nutriets: as they ferment out, you can decant the spent wort and add fresh wort on top of the yeast, and they will keep on multiplying.

Click to expand...

That's what I do (make a starter, cold crash it, decant, and add new wort) so can say from experience that your friend is correct. Of course, adding your starter to another, larger starter also works.

1. Thats what I do, small vortex
2. I am usually doing 1 vial to 4 litres for a starter into 10 gallons
3. I use the foam stoppers

That of course doesn't mean that many other methods won't get the job done.

Piotr said:

Myth no 3: Aluminium foil

Aluminium foil is not the best medium to cover the flask, the air exchange is not sufficient. Microbiologists prefer to use a tight cork made of coiled sterile cotton-wool

What do you think? True or false?

Click to expand...

I would say most microbiologist would use foam plugs. The coiled cotton wool is a bit old school (it is a blob of cotton ball wrapped in a piece of cheese cloth). They are more likely to be found in the lab of a professor that has been around for a while. Their advantage is that they are cheap to make (ie have a poor undergrad/grad student make them) and they last a long, long time. Unless one has access to an autoclave, they would be a pain for the average homebrewer to use. A foam stopper can be soaked in Starsan or Alcohol and then easily squeezed out.

You are correct on the others

Many folks (with the old professor exception, as mentioned above) now use plastic caps that have ribs that allow for friction fit and will slip onto straight sided culture flask necks or tubes. The ribs stand off and allow for air flow. The plastic's easy to clean and autoclavable (polypropylene).

That is, when they don't just use completely disposable stuff.