a serial extraction¶

Percolators work by boiling water to push it up the tube, where it then constantly performs a serial extraction of the coffee, which then falls back into the same water that's boiling to repeat the cycle. This means that the first stage of percolation is extremely dilute... https://t.co/GaOSLBmmNi ... and it only gets progressively stronger as the boiling continues. Since you are trying to extract coffee with an increasingly concentrated solution, the extraction actually becomes less and less efficient as it progresses through the cycles. The combination of needing to reach the boiling point before the process will even start, plus the increasingly inefficient extraction, means that it takes a lot of time and heat to get your coffee to the desired strength. The high heat and long extraction time also means that you end up pulling out a lot of the organic compounds that normally get left in the coffee by conventional brewing methods. These "tail" compounds (which are a bit harder to extract) are larger and much more bitter. On top of the bitterness of over-extraction, some of the compounds that get extracted earlier in the process are getting overheated and undergo further chemical changes during the brew, leading to a burnt taste. Others are volatile, and evaporate off along the way. So with a percolator, you lose a lot of flavorful compounds, alter others, and extract a bunch of "extra" ones, compared to drip coffee. For many people this leads to a much worse tasting cup of coffee.

Taste is, of course, subjective, and you may very well prefer that flavor. The main reason percolators fell out of fashion is likely simply the time and the finickiness. You have to let it sit for longer than a drip coffee maker, and you have to manually stop it when it reaches the desired strength. The weaker you like your coffee, the less of an issue. That's all for now! Tune in next time, where I discuss the chemistry of espresso, which uses a totally different extraction process!