When I was in college, we’d pack the elevator with students, turn off the lights, and yell “Molecule!” The car shook in the shaft as we bounced off of each other and the walls, finally tumbling out when we reached the 5th floor. Chemistry classes were having an applied impact on us, and soon we adapted our game, calling out “Boil!” to speed up our molecular bouncing and “–100 Kelvin!” to slow ourselves into molasses-like movements. Thus chemistry met performance art (mixed once in a while with beverages of the adult sort).
Heat, if you recall from your chemistry classes, is the result of a material’s kinetic energy. And temperature is a measure of that energy. When something heats up, its atoms and molecules move around quickly. When it cools down, those atoms and molecules move more slowly.
Without having to understand the nature of atoms and molecules, humans have long observed that heat and cooling can affect the longevity of food. The apple cellar—a hole dug under a house to use the insulating and cooling properties of the soil—was long a fixture of pre-refrigeration food storage.
As Harold McGee, rockstar writer of On Food and Cooking, the Science and Lore of the Kitchen, notes: “The most effective way to prolong the storage life of fresh produce is to control its temperature....A reduction of just 10 °F/5 °C can nearly double storage life.” He notes that different fruits have different storage temperatures and have to be viewed individually based on their storage ranges.
Take, for example, peaches and nectarines. Now we all know that the best peaches and nectarines are picked fresh, unrefrigerated, and eaten soon. However, if you want to extend their storage lives, you can refrigerate them, but only between 32.5–35 °F or above 46 °F. The range 36–46 °F will make the inside around the pits mushy. Stone fruits are vastly different from, say, apples, which don’t have a “killing zone” of refrigeration, and if kept above freezing will keep for a very long time.
Right now—winter time into spring—we are in the biggest transition period for produce in the U.S. Fresh-picked citrus will begin to wind down, and we’ll start to see domestic apples and pears that have been cold-stored to preserve them. We want to have complete transparency in our mixes, so please be aware at this time of year that if you see grapes, blueberries, or stone fruits, they are coming from the southern hemisphere. We do this to keep the mixes interesting for you, but we look forward to getting most, if not all, of our fruit from the local farmers we work hard to support.
Enjoy & Be Fruitful!
—Chris Mittelstaedt, firstname.lastname@example.org