Scientists from the University of Bath, in collaboration with a local cafe, studied the effects of grinding beans at different temperatures — from room temperature all the way down to a chilly -196C. (I guess they figured some people like to store their coffee beans in vats of liquid nitrogen.) As the researchers point out in their ensuing study, now published in Scientific Reports, we get more bang for our buck when we grind cold coffee beans. That’s because the particles within coffee beans get tighter as the temperature gets lower. So during the brewing process, we get more flavour from the same amount of coffee.
Like almost anything in the kitchen, brewing coffee is an act of chemistry. Ideally, we’re trying to coax as many tasty organic molecules from the roasted bean, which has been ground into tiny bits. The flavours that come of of these coffee bean particulates depend on a number of factors, including water chemistry, the accessible surface area of the coffee and, as the new study shows, the temperature of the bean when it was ground. As the researchers point out, small and uniform coffee grounds allow for better extraction of the flavour compounds, which allows for more coffee per bean, and consequently more flavour.
“What you’re looking for is a grind that has the smallest difference between the smallest and largest particle,” noted Christopher Hendon, a chemistry PhD student at the University of Bath. “If you have small grinds you can push flavour extraction upwards. We found that chilling the beans tightens up this process and can give higher extractions with less variance in the flavour — so you would have to brew it for less time or could get more coffee from the same beans.”
Hendon said this alters the taste of coffee because “subtle changes in particle size distributions make a huge difference in rate of extraction”. His team’s research also suggests that the temperature of the bean needs to be more constant to achieve consistent grinds, and that cooler temperatures maximise surface area, allowing more of the coffee bean to be utilised.
Study co-author Maxwell Colonna-Dashwood, the co-owner of Colonna & Smalls, believes this will have a major impact on the coffee industry, both in terms of how baristas might choose to brew their coffees, and how providers will store and ship their goods to vendors.
“All of this will impact on how we prepare coffee in the industry, I bet we will see the impact of this paper in coffee competitions around the globe, but also in the research and development of new grinding technology for the market place,” said Colonna-Dashwood. For example, this might mean that it’s OK to cryogenically store coffee.
Interesting study! It certainly bolsters the idea that we should keep our coffee beans as cool as possible. As with any study involving taste, a truly good cup of coffee lies in the taste buds of the beholder. In this context, more flavour doesn’t necessarily imply better. But who likes bland coffee?