Hot cup of science

Ironsmith Coffee Roasters officially opened its Encinitas roaster shop to the public in February, the culmination of a year-long effort by rock-climbing cohorts Raul Macias and Matt Delarosa. Prior to founding Ironsmith, neither had experience working in the service industry, so they spent much of 2014 delving deep into specialty coffee. They began by visiting established West Coast shops to research menu basics, equipment, and design. They bought a sample roaster and began cooking beans, working by trial and error to refine their process. And when it came to brewing the perfect cup, they turned to science.

Precision brewing is nothing new in this industry, but seeing it through the eyes of a young roaster reveals how many variables are at work. “I knew I had this huge learning curve,” says Delarosa about the meticulous steps he took to ensure the coffee they served at Ironsmith would be worth the cost to consumers every time. “I was, like, ‘Okay, we’re making coffee, but there’s nothing quantifying what we were doing; everything is so subjective.’”

So, he bought a refractometer specifically calibrated to measure the “total dissolved solids” present in a brewed cup. The device measures the speed of light traveling through a drop of coffee to give an exact number describing the coffee’s strength or weakness. Based on that number, Delarosa says you can tell whether a cup is too strong or light without tasting it.

“Depending how strong or light you want your coffee, you have this target of, say, 1.1 to 1.5 [percent],” Delarosa points out, referring to standards set forth by the Specialty Coffee Association of America and similar trade associations in Europe.

Monitoring the dissolved solids and water-to-coffee brew ratio, Delarosa could track other numbers as well. “What’s probably even more important is extraction yield,” he says, meaning the exact percentage of soluble coffee extracted during the brewing process. “Seventy percent of the soluble mass of coffee isn’t extractable in water — it just won’t dissolve. So, you can only physically get 30 percent of the physical mass of coffee into your cup. But that doesn’t mean you want to have 30 percent.”

The sweet spot for extraction yield falls between 18 and 22 percent — too high, he says, and a coffee tastes bitter; too low, and it becomes sour. These results guided Ironsmith’s brewing techniques, allowing them to adjust grind size and flow rates to pinpoint their ideal.

Lastly, Delarosa points out that more than 98 percent of a cup of coffee is water, and “If your water tastes bad, your coffee is going to taste bad.” He consulted the San Dieguito water quality report to learn how many undesirable elements were in Encinitas tap water, and filtered it accordingly. However, perfectly pristine water isn’t ideal either, as some minerals block the extraction of those unwanted bittering agents. So, the last filter met by the Ironsmith water supply remineralizes it according to Specialty Coffee Association standards, resulting in the levels of pH, alkalinity, sodium, and calcium deemed optimal for brewing.