Storing Coffee
Green coffee beans need to be stored at constant low temperature (not more than 20°C) and humidity if they are to last beyond 2 years with their flavour intact. Roasted coffee beans need special conditions if they are to last beyond 2 days, and ground coffee beyond 2 hours.
The enemies of coffee flavour are oxygen, moisture and light, more or less in that order. Roasted coffee exposed to the air gives off carbon dioxide and various other gases, and also the more volatile of its flavour components. The coffee oils in which most of the flavour and aroma reside react with oxygen and become rancid. Moisture penetrating the coffee dissolves the same components that you want in your brewed cup, and then exposes them to vastly increased chemical reaction rates. Light and heat increase the total amount of energy available to drive these undesirable reactions.
So storing coffee is really about keeping it cool and away from oxygen and light. I sell my beans and ground coffees in valved, laminated foil bags because short of packing in sealed tins this is the best way to ensure freshness.
Why and how? Well, the reason I use valved bags is because freshly roasted coffee releases large quantities of gas, enough to actually blow up a completely sealed bag until it bursts, or blow the lid off a 3kg capacity sealed tin in the boot of the car on a hot day. I don't think my heart or the boot will ever recover from the experience!
The valve lets excess gas out but does not let oxygen and moisture in, thus prolonging freshness. The laminated foil provides an effective barrier to gasses and also to the light. Finally, the out-gassing of carbon dioxide from the coffee fills the bag with inert gas.
The first thing I recommend with these bags is to put them into the freezer unopened if you are not going to use them immediately. I ran an experiment to see how long freshly roasted and ground coffee packed in this way and then frozen will stay fresh. The result was 12 - 13 weeks before taste changes became apparent to me. The same coffee stored at room temperature in a pantry was losing its fresh taste after 4 weeks, so packaging can only do so much.
Note that whole bean coffee would probably have at least double the lifetime of the ground coffee.
It's important to note that the vacuum (brick) packed ground coffee you see in supermarkets has to be stale before you open it! All the gases (and flavour) have escaped before packaging, otherwise the bags would blow up.
The second important thing to note about storing coffee is that un-ground beans will keep much longer than ground coffee…the reduced surface area cuts the exposure to all the staling factors. Grinding just before brewing has always been the best way to go. The third important factor is commonsense food handling; ONLY FREEZE AND THAW COFFEE ONCE.
Right. So you've got your bag of ground coffee out of the freezer, thawed it out and opened it up, and brewed your first fabulous cup.
Now you've still got the better part of a full bag left..what do you do with it? Well, personally, being a relaxed sort of bloke (female portion of population can substitute "lazy bugger" for preceding phrase) I try to grind my coffee only once a week.
After that I store it in an airtight glass jar in the bottom of the fridge.
After six or seven days it is starting to lose flavour, but unless I'm at Death's door or doing an unusual amount of cupping it's all gone by then.
My favorite storage vessel is an old Moccona jar; cheap, readily available at Op Shops and holds exactly 250g.
One disclaimer to all of the above: if you are using an espresso machine and looking for the maximum flavour and crema (aka: the “Espresso God Shot”) there is no substitute for freshly roasted coffee ground immediately before brewing.
The thing to remember about the whole process is that there is no substitute for starting with fresh coffee!
Whether you buy from me or any other roaster, your coffee should not be more than 4 or 5 days out of the roaster at most, regardless of how it's stored.
Personally I seal my own products in airtight 3kg steel pails as soon as it has out-gassed for 24 hours, and turn it over once or twice a week. ANY coffee bought in a supermarket, no matter how famous the brand, is months old before you drink it. "Stale as old boots" is an appropriate description.
