Sunday, 21 September 2014

The easiest way to aerate wort (or how to do less work and get better beer).

Yeast like oxygen, everyone knows this, but if you don't (and even if you do it's worth revisiting) John Palmer has a whole section on Yeast and Oxygen in How to Brew so there's no excuse.

I like many other brewers have spent 10 to 15 minutes each brew day thrashing the hell out of my cooled wort with a big spoon in order to get some oxygen dissolved and a the yeast a good start in life, Mr Palmer lists shaking, pouring and finally pumping air or O2 through the wort.

Always on the lookout for a way to improve my process (i.e. do less work and get better tasting beer) I had considered investing £20+ in a pump system, or maybe even a bottle of pure oxygen.

However, I stumbled across a couple of forum posts about the Venturi effect. Basically manipulating the flow of an liquid or gas so that the pressure drops and causes a vacuum, and using this vacuum to either drag in a liquid like an airbrush does or drag in a gas, which is what we want to do.

You can create this effect by constricting the flow and then expanding it again, at the point of expansion the pressure is lessened and if you place a strategically placed hole suction will occur.

While this image is using air, the same effect works with a fluid.
This approach means you have to make something, then put a small hole in it etc, it all seemed time consuming and as it would be on the cold-side, sanitation was a worry.

I happened to have some nylon 1/4 (6mm) hose connectors, I'd bought them to make a pumped corny keg cleaning system (which I still need to do). I thought I'd have a play around with a three-way connector.

The result is, as you can see, a constant stream of bubbles of air mixed with the liquid as it falls into the fermentor, by the time I had 23ltrs in the fermentor the foam was touching the lid. At least as good as ten minutes thrashing with a spoon, and I'm not having to stand over it wasting energy.

It really is that simple, leaving one of the connector ends unconnected means that as the wort flows through it sucks air in the open end, and bingo, effortless, free (nearly) wort aeration!

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