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