Keeping Coffee Fresh: But Not Too Fresh

First, let's identify the two main processes by which coffee degrades at home.

Diffusion

• Aroma dissipates over time

• The more surface area exposed to air the dissipation increases

• Every time coffee is exposed to air, aroma trapped in the air is released and new space is created for diffusion process to continue

Oxidation

• Oxygen in the air contacts beans/grounds and destroys the flavor

• Every time the coffee is re-exposed to air it increases contact to oxygen and accelerates this process

• Coffee contains lipids (fats), and these can contribute to coffee going bad or becoming rancid due to oxidation or humidity

Storage

• Store beans in an air tight container with as little extra air (space) as possible. This reduces diffusion and oxidation

• Store in dark and cool temperature

• Use a container that minimizes air space inside

  • The less air available for aroma to diffuse into means the less the coffee can diffuse overall

  • When the air is released/refreshed (i.e. opening the container) then this eliminates equilibrium reached and creates more space for further diffusion

• Use a container that is impermeable to air and do not open coffee container more than you have to

  • Every time the coffee is exposed to air it furthers oxidation

• Do not store open coffee in fridge, store in cool, dry, dark space

  • Water molecules in humidity attach to coffee and increase diffusion process

  • If you expose your coffee to cold and warm air repeatedly (opening fridge and container), you increase humidity exposure

  • Light increases chemical reactions and possibly oxidation

  • Heat increases oxidation and diffusion, so storing in a cool place is best

Slowing Down the Process

• Freezing can prolong the quality if needed

  • Beans must be stored in an air tight container

  • Beans must sit out to thaw 2-4 hours at room temp before opening bag

    • Otherwise the rush of air and humidity could destroy quality

    • There is a school of thought that grinding a dose of beans directly from the freezer could benefit in the grinding process by decreasing heat and friction from the grinding burrs

  • Beans can hold quality for months in the freezer, but once defrosted they are now only good for maybe a week

  • It is best to freeze small batches to take out as needed so you do not reseal bag with exposure to air and increased humidity

    
    

• Do not ground beans until you need them

  • Beans offer less surface area for oxygen to oxidize

  • When you grind coffee you create millions of particles rather than one bean, hence, more surface area exposed

    
    

• Purchase whole beans fresh and store in fridge or freezer until ready

  • When you get a new bag of beans, keep the bag sealed and place in fridge or freezer until they have aged according to roast level

  • Once ready, take the bag out and set on the counter for 2-3 hours until they have reach room temperature

  • After initial use, store in your container and do not put back into fridge or freezer

    • If you do not have a container (often due to multiple bags of beans) you can the beans in their original packaging

      • Remove all air in the bag, roll up tightly, put a rubber band around it

• Age fresh beans according to roast date

  • You have to allow time for CO2 to release that has been trapped during roasting process

  • The darker the roast the more porous, so the CO2 dissipates faster

    • Light Roast: Use 2-4 weeks past roast date

    • Medium Roast: Use 10-14 days past roast date

    • Dark Roast: Use 5-7 days past roast date Enjoyed this article? Explore much more specialty coffee articles, educational resources, and my latest projects at KeithLyons.org. If you're passionate about specialty coffee, don't miss my book, The Complete World of Coffee; a comprehensive guide to the history, science, craft, and culture of coffee. Learn more at Keithlyons.org.