A new study found there are some added benefits to keeping the coffee in the fridge, which not even the best baristas know. Namely, the colder storing temperature enhances flavor.
To see how storage affects the quality of coffee, researchers at the University of Bath collaborated with a local café and ground coffee beans stored at various temperatures. The beans were stored on the counter (room temperature), in a fridge, freezer and, to push to the extreme, in vats of liquid nitrogen (-196 degrees Celsius).
The flavor of coffee depends not only on the quality of the beans themselves, but also how these become grounded. Like anything in the kitchen, brewing coffee ultimately comes down to chemistry. The smaller the coffee particles, the better the flavor can be extracted with the boiling water because the particles share more surface area. Even distribution also helps extract the flavor better.
“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 flavor extraction upwards. We found that chilling the beans tightens up this process and can give higher extractions with less variance in the flavor—so you would have to brew it for less time or could get more coffee from the same beans.”
Grinding coffee the proper way might not be on the top of your list when brewing coffee is concerned, but subtleties can make all the difference at some point. In this case, the difference between a stale and a rejuvenating brew. For the industry, though, these findings could help coffee companies with their turnover. The uniform, cold beans can cut on waste because more flavor is being extracted.
Among baristas, though, the findings are sure to stir controversy. Many believe freezing coffee beans is bad because it cracks the beans, attracts water from the freezer, promotes accelerated degradation after the beans are thawed or breaks down the flavor oils in the beans. None of these views are supported by science, and there are as many favored storage methods as are professional baristas, and each brewer thinks their method is right, and the others are wrong.
As far as I can tell, this is the only study which actually investigates the relationship between freezing beans and flavor. So, at the end of the day you're welcome to try any method you'd like, but if you're serious about science-based coffee brewing, keep those beans in the freezer.
"The research suggests that temperature of bean needs to be more constant to help us achieve consistent grinds. It suggests that cooler temperatures will allow us to maximise surface area and utilise more of the coffee. 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 Maxwell Colonna-Dashwood, the owner of the cafe which worked with the researchers.