Coffee Science with Four Barrel's Alex Powar

We're talking chemistry. Sort of. "Chlorogenic acid, for instance, esterizes into quinic and caffeic acid. Quinic acid...so that produces a lot of bitterness. That's why you never want to reheat coffee. It catalyzes that reaction."

Alex Powar is talking chemistry — the chemistry of coffee. We're sipping espresso in Caledonia Alley, right behind San Francisco's Four Barrel Coffee, where Powar works as director of research and education. Originally a pre-med student back east, he encountered the coffee world through a training program while working in a Palo Alto restaurant. He now trains baristas and the public on how to make the best coffee possible.

Full disclosure: I'm a regular, and I'm really enjoying the espresso.

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Nathan Explains Science: One of things I'm really interested in is what do people who aren't professionally scientists think about science and think about how that plays a role in everyday life. And coffee's an interesting place for me to start, because it seems like there's some overlap there, and it's one of those things where there's a lot of technique involved and also perhaps a bit of mysticism as well.

Alex Powar: A lot of joining between science and craft, I think, which is common in a lot of different craft disciplines. But coffee is essentially a solubility reaction, so actually over the course of the past century there's been a lot of research done in chemistry labs and physics labs about what makes coffee tick. We have the breakdown of particular acids, how they contribute to flavor. Cloragenic acid, for instance, esterizes into quinic and caffeic acid. Quinic acid —

As in quinine [the chemical that gives tonic water its flavor]?

Exactly — so that produces a lot of bitterness. That's why you never want to reheat coffee. It catalyzes that reaction. 

Let's talk about that a little bit more later on. I wanted to first find out a little bit about you. First of all, where are you from?

I grew up in Palo Alto. My dad's a doctor, my mom's a nurse. That was my path. So, yeah, I did my education at Wesleyan University in Connecticut, and I studied Pre Med.

Wow. So you were thinking you'd maybe be a doctor.

Yes, that was my intent for a pretty long time. I decided at the last minute that it wasn't for me, partially as a result of the liberal arts courses that I did. I studied this program called Science and Society. After I graduated I wanted to be an academic...and my parents said "no, you have to get a real job." [laughs] "You have to go to medicine or else." I decided to go "or else."

I started working for a restaurant, with the goal of maybe going into food. They were buying coffee from Barefoot Coffee at the time and for all their wholesale accounts, their wholesale baristas went through sixteen hours of training, so I learned a lot. [They] really encouraged passion in coffee preparation.

I'm really methodical, and I think what interested me in food is an understanding of the kind of mechanics of what makes food really good, when it is really good. The language that they were using around coffee at Barefoot was closer to where my interests in food lie. And also the integrity of people in the coffee industry tends to be really high. That's not saying that people don't have great integrity in food as well. But it seems to be less of a financial motivation, more just like we're going to seek out the best quality coffee and try to prepare it the best we possibly can. Be really uncompromising about it.

What was the word you used — you said what interested you about food and coffee was—

Mechanics.

Mechanics. So when you say mechanics, what does that mean exactly to you?

Literally, what is happening when you heat a pan to a particular temperature, what physical changes are going on in the food that produce like a better steak or a worse steak. Kind of like the breakdown of particular things at particular temperatures. You know, braising leeks, for example, the breakdown of cellulose. 

And in coffee we see that a lot as well. People who are most successful in the coffee industry - there's a lot of intuition involved, and coffee preparation, but that only takes you so far. Having a knowledge of physical and chemical interactions in coffee, like variables, being very specific about keeping track of the variability in these products is really important for consistency. Otherwise if you brew coffee one way, and it's great, it can be a total fluke. You don't understand what's going on. 

The word artisanal gets thrown around a lot these days. Do people think of it in that sort of old-timey craftsmanship sort of way? Or is there more of a movement toward toward talking about the chemistry of coffee? Is there a balance there, or is it one way or another?

I think the biggest problem in the coffee industry, a lot of people will tell you, is a lack of systemized education, and I think that kind of precludes us from having that kind of information, you know? Artisanal production of anything always requires a certain degree of juju, and that kind of intuition, kind of feel. As an educator here at Four Barrel, moving forward, I hope to build an education program that provides people with the skills to be able to make much more informed decisions in coffee. We do really focus on precision here and understanding the basics of what's happening in coffee — literally physically what's happening with an individual coffee particle, when you run a solvent through it.

Do you want to have everyone here understand that, or—

Yeah. I don't think you can be a good barista without understanding what's happening on that scale. The resources for everybody to have that kind of knowledge just don't exist quite yet, so it took me years to accumulate of talking to the right people and working in the right places.... My job essentially every day is to make coffee taste better and take as much time as I need. 

How do you go about making coffee better, whether that's taking a certain amount of time just to make coffee and taste it yourself, or making it better for other people.

There's a lot of A-B testing involved. It's very coffee dependent too, so you need to set a certain number of controls using the same coffee on the same roast date on the same grind — kind of finding what your variables are, then altering one at a time. Like you were saying earlier coffee is this weird hybrid between the more systematic elements, you know? These are the variables, you can alter one or any of them, but also kind of like how this understanding ties into an overall flavor. So our goal at Four barrel is to source coffees that are fruit-forward and really floral that remind the customer, the last link in the chain, remind them that it comes from a place, that it comes from a fruit, that it's grown on a shrub, and coffees that really taste like origin, that taste very specific to a place. Then we roast it to really amplify that. and our preparation method, that's our goal as well. It's a really funny ingredient in that you can treat it really well on any link in that chain, and then completely screw it up in the end. And you can also make it taste really good, but you can interpret it in such a way that it's really far from our overall goal, kind of like what we're trying to represent in the coffee.

So generally, to answer your original question, generally when I'm running brew method experiments, I look for existing brew methods, see how well they play in my understanding of whats going on in coffee on a physical level, and then essentially just brewing a ton of cups, just altering one variable at a time, seeing, what if I take this in this direction, what's that going to do?

Thanks to Alex Powar for taking the time to talk coffee and science. Thanks also to Four Barrel’s Matthew Hein for helping set up the interview and roaster Sarah Bouldin for letting me taste freshly roasted coffee beans — they were yummy.