I understand that it pays to store freshly ground coffee in the freezer. What about instant coffee or cheep prepacked Turkish coffee?
In chemistry it is generally accepted that a reaction rate drops in half for each 10 degrees in C drop (about 20 degrees Fahrenheit). So oxygen would still oxidize the freeze dried coffee, but at a slower rate.
It's ok to store freshly grounded coffee or instant coffee in a freezer. Just consider to:
- Pack the coffee in a sealed package or container.
- Avoid keeping coffee with some other high fragrances items such as vanilla essence, rose water etc as these things can affect the main coffee essence.
Here is a source on How to Store coffee that has a clear explanation.