Storing & Preparing Your Coffee

Let us start by addressing one of the biggest points of confusion in the world of coffee. Many individuals within the specialty coffee industry labor under the misconception that the freezing of roasted coffee beans will adversely affect the fats that are present, in a manner that is similar to the freezing of cream. This is completely false. The fats in cream have formed mycelium (microscopic globules) and are in colloidal suspension. If this colloidal suspension is challenged by freezing, the mycelium break apart and the suspension collapses. In contrast, coffee beans are solid and the fat is supported by solid cell structures, and no such collapse is possible. Freeze your coffee beans, but pay close attention to the following discussion.

The storage of your precious coffee is extremely important, and there is considerable confusion, at all levels, as to what the proper methods are. Not only did we spend three years researching this aspect of coffee at all levels in the specialty coffee industry, but we retained the services of a chemist, who specializes in the chemistry of coffee, to provide unequivocal direction in this area. The following rules will provide you with the guidance you need to protect the quality level of your coffee beans.

  1. Don't let coffee beans come into contact with oxygen. Oxidation in coffee beans is the number one factor in causing coffee to go stale.
  2. Don't let coffee beans come into contact with moisture, either in the liquid or vapor forms. Water vapor will condense when cooled down to form liquid water. Just remember that the water vapor contained in air at room temperature will condense into the liquid form when the air is cooled down to a certain temperature, referred to as the "dew point". The exact dew point depends on the amount of water vapor (relative humidity) contained in a given quantity of air at room temperature. Rest assured that your refrigerator, and certainly your freezer, will produce the condensation of water from room temperature air. Water greatly increases the oxidation within coffee beans, and the presence of water in coffee beans leaves them in a very unstable condition.
  3. Don't let coffee beans come into contact with light. Aside from raising the temperature of the beans, light will dramatically increase the chemical activity on the surface of the beans.
  4. Keep the temperature of the beans as low as possible. Lowering the temperature reduces the rate of all chemical activity in the beans. A popular misconception we've found is that people, both at the consumer level and the industrial level, believe that if all the oxygen and moisture are removed from the atmosphere surrounding coffee beans, the coffee will not go stale. Not true! There are chemical reactions going on inside coffee beans that do not require oxygen, and are referred to as "anaerobic". These anaerobic reactions can never be stopped, and will eventually destroy the quality of the coffee. They can, however be considerably slowed down by lowering the temperature. The lower the temperature the better. If you have opened a bag of coffee that was packed in nitrogen, the atmosphere will eliminate the protective benefits of the nitrogen. If you don't plan to use all of this coffee within a few days, you should repack the coffee in Zip Lock plastic bags. Each bag should contain the amount of coffee you consume in a few days. The plastic will prevent air and water from entering, but it will not prevent the loss of crucial flavor volatiles. If the coffee is going to be stored for a long period (such as weeks) you might consider wrapping each plastic bag with aluminum foil which is a perfect gas barrier. Coffee should not come directly into contact with aluminum because the acids in coffee will react with the aluminum.. The temperature in the freezer and your taste sensitivity will dictate if they can be successfully stored for a longer period of time. Six months is quite realistic.
  5. Don't allow frozen, or cool coffee beans to come into contact with warm air, unless you plan to use all of the beans being exposed right away. Remember that warm air contains water vapor which will condense immediately on the cool surface of the beans. The condensed water will be rapidly absorbed into the beans. It is a good idea to take a packet of beans out of the freezer the night before you are going to open the packet.
  6. Do not apply extreme heat to frozen beans or try to thaw them out in a microwave oven. Raising the temperature of the beans too high will restart many chemical reactions that will immediately destroy the quality of the coffee.
  7. Never grind coffee beans until you are ready to brew. Ground coffee simply cannot be reasonably preserved in any way.
  8. If you have purchased pre-ground coffee, all of the preceding principles apply, but be aware that the grinding process has destroyed one of the most significant preservation factors ... the physical structure of the whole bean itself. The coffee bean provides natural layers of paraffin and oil which significantly retard the loss of flavor volatiles and carbon dioxide (carbon dioxide prevents oxidation). These layers of protection also make it more difficult for oxygen to enter the bean. Once the physical structure of the bean has been broken down, the staling process jumps into high gear and races ahead of any known technology to control the degradation.

Further Reading

A Question of Freshness - by Paul Songer