Controlling fermentation without a lab
Brix, temperature, and the nose.
Three instruments
A refractometer, a thermometer, and a person who smells the tank every two hours. That is the entire control system on most Taiwanese farms.
Brix tells you how much sugar the microbes have to work with; temperature tells you how fast they will do it.
The most important instrument on a coffee farm has no display.
The nose
Healthy fermentation smells of yoghurt and stone fruit. When it turns to vinegar or nail polish, the batch is being lost and no measurement will say so faster.
This is why experienced growers trust smell over numbers, and why the skill does not transfer easily.
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