Last year we published an article based around the unique possibilities now available through pressureprofiling, and to emphasize this we kept our grind size setting constant for six months. Afterwards, the work continued and we began to look deeper into the study of particle size analysis. This was possible through collaborating with the qaqc coffee lab as we used their digital imaging particle size analyzer. The important distinction between digital imaging and laser diffraction is that with digital imaging you are also able to assess the shape of particles, see an image of each particle, and not just graph their size as can be the case with some laser diffractors.
Whether it is the temperature of the beans being ground, the environment temperature, or the starting density of a bean determined by its origin or roast degree - it’s suffice to say that each coffee is bound to break up differently when ground. Having experienced this for years on bar we got to see it for the first time as we ran five coffees on our tasting bar menu through one grind setting and graphed the curves created through a DI particle size analyzer.
When reading the graph below know that each point on the curves correspond to a particle size range or ‘bin’ that might, for example, represent all the grinds ranging from 200um-220um and the percentage of the sample they make up. If the curve sits high on the graph - a larger percentage of the particles are in smaller size ranges - or a finer grind in effect. If it the curve sits lower on the graph a higher percentage of the sample was in the larger bins - making for a coarser grind.
One of the standardized variables of a cupping program is the grind setting used. If the average particle size created on one setting will be different for each coffee, we can expect their extraction rates to be different as well and have noticeable flavour impacts in the cupping bowl. This only becomes an issue if what you’re tasting at this stage is what all of your quality control adjustments are based on. You may unnecessarily be adjusting the roast degree on certain coffees in order to have all of your offerings performing similarly on your fixed cupping grind setting; which of course stops being the context they’re brewed in once they arrive at a cafe.
This is why completing the brewing work by putting each coffee through the major brewing methods of espresso, drip, and immersion allows you to better understand how your coffees will translate once they leaves the roastery.
Sample roasting and cupping alone aren’t complete without extending the work to developing brew parameters , and only by using these three practices together can we achieve the optimal flavours found within each of our coffees.
Yours in Coffee - Pilot.