Has anyone ever measured how the conductivity of fermenting liquids changes over time?
I have a hypothesis that it does change over time, and that as the fermentation rates and stages change, so will the capacitance of the wort. Also, that one will see more capacitance change during early fermentation, but it will settle down to a steady value as fermentation dies down, flocculation occurs, etc.
Why do I ask? I would like to digitally measure fermentation activity without directly sampling to measure specific gravity. Measuring SG would be great, but what I'm really interested in is activity level of fermentation. I'm not trying to calculate SG - I'll do that when I transfer the batch from primary -> secondary -> bottling. I'm thinking though that seeing that conductivity value level out is what's the signal for when to transfer.
I've found online that seem to say this might be worth pursuing a bit. For example here is a paper titled, "Electrical conductivity as a tool for analysing fermentation processes for production of cheese starters" http://www.sciencedirect.com/science/article/pii/S0958694600000601
Another article at http://www.springerlink.com/content/9m42027266477mj2/ mentions, "We describe the interest of on-line monitoring electrical conductivity and his good correlation with pH during fermentation. The change in conductivity is primarily due to the assimilation of nitrogen (in particular, ammoniacal nitrogen), which is usually the limiting nutrient of the fermentation kinetics."