So, for espresso, we know that shots will be overextracted when we see blonding. You can tell a lot about a shot's taste by looking at the color of the extraction.

Can a similar principle be applied to pour over? Something like: bean X blondes 60 secs at 210 degrees, but blondes later at 195 degrees. We know temp influences extraction. If such a correlation between color and extraction exists, could that visual information not be used to guide a brewing recipe for a particular bean or guide pouring while brewing?

That's not even true for espresso, especially with lighter roasts.

Looking at the color of espresso as you are extracting seems to give some indication of taste/extraction; the color and flavor of the initial drops (dark and sweet) are very different than the latter drops (light and bitter)...perhaps color is not the variable to focus on?

I guess, then, the overarching question I have is; how can extraction be gauged *during* a pourover?

Or - is it all taste, adjust, and repeat?

I think I am getting to a point where I am going to pick a procedure and only alter grind size and temp - at least to start.

I've never noticed a relationship between the quality in the cup and the color of the foam when brewing coffee.

I *have* noticed a difference when there was NO foam at all and the quality.

As with crema, the foam is produced by escaping CO2 being trapped in coffee oils. When there is no foam, that usually (but not always!) means one of two things: the coffee is stale and there is no longer any CO2 to escape, or the brew water is over-chlorinated.

I used to live in one town and work in another, just far apart enough that they were using different municipal water supplies. I was using the same beans, grinding with the same grinder immediately before brewing, same brewer, and my coffee at home was decent, and the coffee I made at work was barely drinkable. I didn't put two-and-two together until I realized the Caribou Coffee kiosk in the lobby of my workplace was suffering the same issue. But one thing I noticed was that there was zero foam on the surface of my coffee at work, and the chlorine smell was strong.

I've been following water recipes and should probably start to see if I notice any differences across water.

In your experience the bubbles might predict a taste quality where release of co2 is favorable. At some point release of co2 stops during the brewing. I'll have to play with that: maybe taste coffee extracted during high co2 release, low co2 release at the end of the brew, and both together.

smt wrote:So, for espresso, we know that shots will be overextracted when we see blonding. You can tell a lot about a shot's taste by looking at the color of the extraction.

Can a similar principle be applied to pour over? Something like: bean X blondes 60 secs at 210 degrees, but blondes later at 195 degrees. We know temp influences extraction. If such a correlation between color and extraction exists, could that visual information not be used to guide a brewing recipe for a particular bean or guide pouring while brewing?

I think the over-extraction relationship with blonding is more to do with temperature for x time than it is time alone. The idea being if you extract something too long with too high of heat then you get those over-extracted flavors and blonding in this case is a time variable. However if you lower the temp of the water you should be able to extract longer before those unpleasant tastes come in. This of course changes with the degree of roast and it isn't clear to say when blonding occurs it's over-extracted.