But is the oxygen in the bubbles really absorbed back into the wort, or is it just encapsulated in the foamy bubbles? Once the bubbles bursts, the O2 is just released back into the air, not into the wort. Just like using a stone, if the O2 is bubbling to the surface it is escaping, not absorbing. It would seem that any O2 absorption occurs during the shaking, not as a result of the collapsing foam.
You are comparing apples to oranges. Bubbling a gas through a liquid is not the same thing as a gas-liquid foam. The ratio of liquid to gas is inverted in a gas-liquid foam. A gas-liquid foam is composed of pockets of gas entrapped in extremely thin layers of liquid. O2
is absorbed at the boundary between the liquid and the gas. It does not take long to saturate a liquid when the depth is less than the thickness of a human hair and gas appears on both sides. We are taking about a depth measured in nanometers. The liquid will saturate based on Henry's law. The only way to force more O2
to dissolve is to increase the pressure of the gas (as we do with CO2
when force carbonating a keg). Pure O2
saturates at 40ppm because pure O2
contain five times the amount of O2
Now, the $10,000 question here is do the cells pick up any non-dissolved O2
when the culture is pitched before shaking? Dissolved O2
from air peaks at around 8 parts per million. The O2
in air is 21 parts per hundred. If a wort bubble is the same thickness as a soap bubble, we are looking at a range of 10 to 1,000 nanometers. The diameter of Saccharomyces cell ranges from 5 to 10 micrometers.