Fresh juice is without question a requirement of a well stocked bar, and maintaining a fresh supply can be a bane to any amateur cocktail enthusiast. Citrus left out at room temperature squeezes well but quickly acquires bitter flavors as the fruit ages; storing fruit in the refrigerator can delay the onset of off flavors but at the expense of firmer flesh that can make significantly reduce juicing efficiency. Even fruit kept in the fridge, however, will eventually spoil. With an oft random schedule vulnerable to aging citrus, what is a graduate student to do?
In the past, I would either try to use old citrus (to the detriment of many a cocktail) or swallow the waste and throw it out. After my last big cocktail party, however, I had nearly a pint of freshly squeezed juice that I couldn't bring myself to trash and I began to research alternatives. Eventually my search stumbled upon the unsung hero of preservation: the freezer. Freezing the squeezed juice in 1/2 ounce increments would dramatically increase the effective lifetime while providing convenient serving sizes. Conveniently, one of my ice cube treys held exactly 1/2 ounces in each well. The experiments were on.
My main concern was that the frozen juice would take too long to thaw and limit the convenience of the method. Fortunately, chemistry proved a powerful ally; something in the juice (not sure if it's the low pH or just the solutes impeding crystal formation) reduces the latent heat of the cubes. Build a drink, throw in the cubes, and you'll only have to wait a minute or so before they melt and the drink can be finished with the introduction of ice and a quick shake.
The initial batch of lime and lemon cubes have been in my freezer for over a month now and I have yet to notice any significant reduction in quality. I would definitely pick up some fresh fruit in the case of a party or the occasion to impress someone, but the cubes are definitely sufficient for today's grad student on the run.