Aeration of wort before pitching yeast

[Laripu]

I shake the siphon hose, or shake the glass FV as wort is going in, depending on my mood. I might also use a drop of olive oil.

I tried aeration with a pump, beer stone, and filtered air, and it created much too much foam. That was wasted money for me. I don't want oxygen around, so that's out.

I'm happy with shaking and olive oil. It works for me.

[Cpt.Frederickson]

Think I'll give the olive oil method a go sometime soon. With dry yeast they often recommend to not aerate your wort so these seem like good candidates for the oil method.

[banjokat]

Forgive my ignorance, I haven't read the book yet but what's the olive oil method?

[Laripu]

Forgive my ignorance, I haven't read the book yet but what's the olive oil method?

A tiny drop of olive oil in the cooled wort. I pick it up on a tooth pick, drop it in the wort.

It provides the something that yeast need that they would otherwise get from oxygen. I'll have a look in the book and post later.

[Cpt.Frederickson]

I seem to recall it was to do with sterols. But I'm not certain what they are. Think they're used in cell wall production.

[banjokat]

Thanks, I'll give that a try.

[Laripu]

I seem to recall it was to do with sterols. But I'm not certain what they are. Think they're used in cell wall production.

I'm looking at the book. You're right.

When yeast reproduce, the daughter cells need new membranes, made from lipids. Sterols keep the membranes fluid and regulate permeability.

Yeast can either use available sterols, or make them, in part using oxygen. The membranes also need unsaturated fatty acids. To make them, they do a complicated series of biochemical steps that require oxygen to make the unsaturated fatty acids palmoleic acid and oleic acid.... hence the need for oxygenation.

New Belgium Brewing Company in Colorado tried some experiments. They had a control batch that they oxygenated, and experimental batches which were not oxygenated, to which they added olive oil, which is rich in oleic acid. The most successful used 1 milligram per 25 billion yeast cells, 5 hours before pitching. Fermentation time was about the same (94 hours vs 83 hours for the control). The experimental batch had slightly higher levels of esters and slightly lower levels of fusels, but tasting panels couldn't detect any differences.

They didn't end up using the technique permanently.

So what I do is to dissolve some oxygen by shaking while I siphon into a glass FV, then take a toothpick to pick up a tiny quantity of olive oil, a minidrop, and add it to the wort. That's just before pitching. Available oxygen can be used to make sterols, and oleic acid is available to the yeast via olive oil. Everybody's happy.

It works for me. YMMV, as the kids say.

[banjokat]

Laripu, thanks for that very detailed reply.