Wort – How Much Dissolved Air Will It Typically Hold?

I spent some of last week helping brewers troubleshoot issues with their wort aeration, so this seems like a good time to jot a few ideas about the limiting factors of dissolved gasses.

Gasses dissolve into liquids based upon the ability of the liquid to hold a specific gas. For example, there are hydrocarbons that at room temperature can hold more than 200 mg/L of O2. Compare that to pure water, which holds only 45 mg/L of 100% oxygen gas.  Air dissolved in wort will dissolve in about 1/5 the concentration of pure O2.

Barometric pressure can also have an effect. Imagine you’re injecting air into wort and your brewery is in San Francisco at sea level: The air will hold about 16% more oxygen than if your brewery is on the Colorado Front Range at 5,300 feet, even though the relative percentage of oxygen compared to nitrogen is similar.

Cold liquids have a greater ability to hold gas than warm liquids, so liquid temperature is another important factor in determining dO2 content. The graph below shows the relative concentration of air dissolved in water, based on temperature. The solubility of oxygen in wort is slightly less than water, but as far as I’m aware there is no published literature showing dO2 in wort according to temperature, so that’s why we’re using water as our example.

And here’s the way it looks using the raw data used to generate the graph:

Temp (oC)

dO2 (ppm)

N2 (ppm)

0

14.65

23.51

1

14.24

22.92

2

13.85

22.35

3

13.48

21.82

4

13.13

21.30

5

12.79

20.81

6

12.47

20.34

7

12.16

19.89

8

11.86

19.46

9

11.58

19.05

10

11.31

18.66

11

11.05

18.28

12

10.80

17.92

13

10.55

17.58

14

10.32

17.25

15

10.10

16.93

16

9.98

16.63

17

9.68

16.34

18

9.48

16.06

My final thought comes back to the importance of controlling and closely monitoring those process parameters over which you have control. You may not be able to control barometric pressure, but you can be aware of it. And you do have control over temperature, so that’s another help toward meeting your goal of consistent dissolved gas levels.

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