Measuring DO in wort pre-fermentation

[troybinso]

What is the best procedure for measuring dissolved oxygen in the wort pre-fermentation, in other words, how do you know you are getting the right amount of oxygen in your wort?

[dick murton]

Suitable oxygen meters.

Look up threads for Orbisphere and wort oxygen, and you will find loads of discussions. If you can afford one, get an optical unit, not an electrochemical unit.

Just because you can add a know quantity of oxygen as oxygen, or as air, doesn't mean it will all dissolve, so an instrument is extremely useful, though rather expensive. You should find mention of cheap instruments for water oxygen for fish etc - forget these as they are not accurate enough.

[troybinso]

Wow, those things are incredible expensive. I am a startup with a small budget.

The cheapest one I can find is about $200, and it is meant for measuring oxygen in rivers, etc for fish. It says it measures 0-19.9 ppm, 0.1 resolution, and +/-1.5% accuracy. Will this not be acceptable for figuring out if my oxygenation method is properly infusing the wort with enough oxygen? I am shooting for 10ppm in most beers, and that is right in the middle of the range of this meter.

[dick murton]

I agree that I would always go for an optical sensor rather than an electrochemical sensor (providing of course I had the money to sepnd), but not on the grounds of wasting more beer. The time of response is far faster once the instrument has been purged, and this is often the greater problem in my experience.

But back to the original question with a couple of thoughts:-

1. If you are using fresh dried yeast for every brew, then additional wort oxygenation is not normally required. Sometimes you may need additional air / oxygen into the fermenting wort during the first half of fermentation if brewing very high gravity beers.

2. If you are using air, then a 0 – 20 ppm instrument will be ok as the maximum you can dissolve is less than 10 ppm. If however you are using oxygen, you can achieve up to approx. 30 ppm – assuming everything is dissolved, so the 0 – 20 ppm instrument is not suitable for really high levels.

3. If you have a DO2 instrument, whichever sort you go for, if you don’t have the ability to dissolve the available oxygen fully and consistently, then you cannot consistently adjust any dosing rate. You need to be able to accurately control the gas pressure and flow, (and wort flow rate) and to be able to guarantee the available oxygen is fully dissolved. You really need this level of control before you get bogged down in monitoring kit, otherwise all it will tell you is that wort oxygenation is inconsistent. So my first expenditure would be on equipment to ensure accurate, consistent, calculated dissolved oxygen levels, not a meter.