An interview series with Zocalo's Coffee Roaster, Cathy Davies, and Administrative Manager, Alex Aimee Kist. In part two, Cathy teaches us about the coffee roasting process.
So, let's jump back in!
So you told us last time about how you made your way to Zocalo. But what have you learned here? Can you walk me through the process of roasting?
Sure, I roast coffee on our 25 lbs San Franciscan coffee roaster, who we’ve affectionately named Betty.
Betty! I actually didn't know that. That is delightful. Sorry, please continue.
Betty was manufactured in 1996 and is number 54 in the world. She’s also original to 645 Bancroft, moving to our Roastery facility in 2014, when Sara purchased Zocalo Coffee.
Each batch of green beans is loaded into Betty’s hopper above a cast-iron drum, released into the drum where it spins over a gas burner. The temperature is controlled via gas and air flow and as the beans rotate they will turn color from green to roasted brown. Coffee goes through 3 stages in the roaster: drying, browning, and development.
So what is happening to the beans throughout those stages?
The beans start out as light green and dense with a moisture content of about 8-12%. In the drying stage, as the beans heat up, that moisture starts to cook off. Temperature is key at this point because ideally, the beans will heat up quickly enough to maintain some internal moisture into the next stages but not so fast that their outsides scorch.
After about 4-5 minutes the green beans will begin to transform from green, to a pale yellow, then golden, tawny tan, and into browns. This is the browning stage, where the Maillerd reaction begins. The amino acids and reducing sugars within the beans react with one another to cause the color-changes but also (delicious) caramelization flavors.
Finally, at the end of the browning process, the beans enter the development stage and audibly crack. This is called First Crack. The cracking indicates the beans have become exothermic and have built up enough heat and energy that the energy is released with an audible popping sound, like popcorn. This stage is about 15-25% of the duration of the roast and is where the aroma compounds of the roast are developed and the roast level (light/medium/dark) is determined. This portion of the roast occurs around 360-390°F and can change fast. Constant observation of color and smell is necessary to determine which point to complete the roast.
The First Crack, I like that. That sounds tricky, though. So many things to focus on. How do you make sure they are finished the way you want them?
Roast completeness is determined when the beans have met a series of benchmarks for temperature, time, smell, and visual variables, depending on the intention with the coffee.
That makes sense. So what comes next?
At completion, the beans are dropped into Betty’s cooling tray and she will take overturning the beans until they are cool to touch. In general, a lighter roast will have more nuanced aromas and flavors (floral and fruit flavors really shine here) but consequently can have more acidity. Darker roasts will have a more gentle acidity and fuller body but those more delicate flavors/smells can turn into roasty and toasty flavors. For my tastes, I am more of a medium roast gal, aiming for those bodied caramelized sugar notes while preserving the higher fruit and flavor notes for a balanced cup.
I must admit, I'm very glad to have a cup of coffee in hand while you talk about this! That is all the time we have today, Cathy. But as always, thank you for your time.
To learn more about Cathy, make sure to check out part one of Coffee with Cathy and stay tuned for part three! We hope you keep up with us on social media and our email newsletters!