My colleagues in the Cal Academy's Digitization Team, Anne and Codie, have graciously scanned these beautiful images of coffee beans for me , using our fancy GigaMacro super high-resolution camera system (which I'm calling "Maggie" from now forward.) This was a test to show how the public can get a better understanding of the various applications of digitization technology for scientific research.
From an early age, coffee has long been a central part of my daily existence. My first date was to an all-night diner, where I drank several cups of coffee and assumed that my beating heart meant that I was deeply in love, instead of a normal physiological reaction to 100s of mgs of caffeine. Gallons of the stuff got me through undergrad, typically the instant variety that still makes me retch today. Living in Brooklyn and now the San Francisco Bay Area, I witnessed the explosive growth of coffee culture that started in the late 90s and continues today.
But this is the first time I've seen these precious beans at such high resolution.
The image shows three beans (from the bottom-up) unroasted, a medium roast, and a darker roast. As you can imagine, the difference between the medium and the dark is the amount of time the bean is left in the roaster. Generally, the darker the roast, the less the acidity and more sweetness, with more burnt flavors coming through, whereas lighter roasts are "fruitier" and more acidic and "brighter" tasting.
As I understand it, the main chemical processes involved in roasting are the maillard reaction and caramelization, complex reactions of amino acids and carbohydrates that give coffee its unique flavor.
Comparing the unroasted and the medium roast, you can see the result of what is called "first crack," an audible sound emitted when the coffee bean releases moisture and expands. It still has that silver lining in the middle of the bean, and just a few darker spots.
Moving on the darker roast, you can see the aftermath of the "second crack." The middle section is now totally darkened. This is a delicate part of the chemical process, where timing is critical to avoid getting a roast that is too caramelized / burnt. More oil is released at this point, resulting in a shinier appearance.
Which tastes better is generally up to personal preference. Coffee snobs tend to prefer the brighter flavors of light roasts, whereas most of the general population gravitates toward darker, sweeter roasts (ala Starbucks.) I'm definitely in medium roast territory. I find the acidity of the lighter roasts unpleasant and dark roasts to be just completely bland. I recommend attending a coffee tasting if you can, or just trying out different roasts for a week or so to find a balance that works for you.
Check out this cool video that shows the bean across the roasting spectrum.
You can check out "Maggie" the amazing robotic camera in the California Academy of Sciences' Project Lab during visiting hours.
Thanks to Dave and Eugene at Snowbird Coffee in the Sunset District for providing these beans for us! Visit them at 352a 9th Avenue, San Francisco.