The Moka Pot is an unusual device and not exactly easy to decipher. I’ve learned a lot about brewing coffee with my 3-cup Bialetti in the last few weeks. This is a real short version of what I believe are the key variables that change the brew taste. The post assumes you already know basics of Moka Pot brewing.
Heat application: This is in my opinion the number one variable. Can be controlled on a stove top by getting a good steel heat diffuser which prevents the pot from being directly exposed to the heat. It also needs to be cut off at just the right time to prevent steam rushing through the pot’s lower chambers and scalding the coffee. It really need not be constant throughout the brewing process and is tightly connected to the next variable:
Brew Time: I didn’t realize how important this was until a friend pointed out that my brews were taking too long (8 – 9 mins). On cutting short the brew time (< 4 mins) using pre-boiled water, the sour taste in the final product was noticeably lower. The running theory is that in longer brews the lower temperatures of the water leads to extraction of the sour flavors from the coffee.
Grind Size: The Moka Pot can brew with a wide variety of grind sizes from medium-fine to fine. I believe the finest you can go is when your coffee grounds literally start getting through the upper metal filter in the Moka Pot. Grind size does make a noticeable difference to the taste of the final brew. It’s worth controlling and experimenting with. I’ve found it difficult to go finer if you can’t control the Heat applied. In my early trials where I’d exposed the pot directly to the flame, finer grinds would sputter violently. Once I had the diffuser in place those same brews had a consistent flow.
Other variables include Roast (medium, medium-dark and dark), water quality, coffee dose (the grinds must swell to fill the basket for best results), water volume in the lower pot – all play a role. The coffee quality too is worth mentioning. I was truly startled by Ethiopian Yirgacheffe (medium-dark). It had light qualities I couldn’t find any of our Indian SO or blends I’ve tried so far.
That’s all for now. This post ought to morph into something much more detailed later on.