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The Science of Coffee Freshness

Updated: Nov 17, 2019

Did you know that what you do when your coffee arrives makes a huge difference in how it will smell and taste? We will go over some simple things I recently learned at a scientific lecture on coffee that will make your coffee taste amazing!

At the Specialty Coffee Association’s Coffee Expo, coffee nerds from all over the world converged on the city of Boston. It was one of the only times in recent history when people measured their daily coffee intake in gallons! It was also one of the few times when there was a line at both the men’s and women’s restrooms.

While there, I attended a really interesting lecture by Dr. Samo Smrke from Zurich. Dr. Smrke, a food scientist, conducted numerous experiments to quantify and test factors leading to fresh coffee. He quantified freshness by creating an index based on measuring the concentration of aroma compounds found in coffee. His team found that coffee freshness is most affected by grinding, packaging, and temperature. Here are some things you can do to keep your coffee fresh.

1. Do not grind your coffee until right before brewing. When coffee is roasted, there are air pockets that store carbon dioxide. Grinding increases the surface area of the coffee and allows more carbon dioxide to escape. This will in turn change the aroma of the coffee.

2. Make sure to keep your beans away from oxygen and in a plastic sealable bag. When you buy your coffee, place the beans in a completely sealed bag that allows you to expel the oxygen. While in a container or bag, gases and compounds being released from coffee go through hydrodynamic flow and diffusion. When the coffee beans reach equilibrium with the bag or container they are in, the release of CO2 gases are greatly reduced.

3. Keep your beans in low temperatures. Dr. Smrke’s team found that putting coffee in a consumer-grade freezer decreased degassing by 12.5 times. This means that the longevity of coffee is extended from 1-4 weeks to 3 months to a year. Even if you’ll be using your coffee soon after purchase, decreasing the temperature will keep it fresh.

For a fresh cup of coffee keep whole beans in a plastic sealable bag in your freezer and grind every time you brew.

Source: The Science of Coffee Freshness. Samo Smrke. Presented at 2019 Specialty Coffee Association. Boston Massachusett. April, 2019. See: