Olive oil, walnut oil, flax oil, and other vegetable oils Oils may or may not be hurt—or helped—by refrigeration. It all depends on how delicate they are, how warm your house is, and who you talk to. The issue is flavor versus shelf life. Purists say refrigeration causes condensation to form on the inside of the container, which may harm the taste of a very delicately flavored oil. Oil may also become cloudy and slightly solid at cold temps, and while it will liquify when returned to room temperature, repeated solidifying and melting may change the flavor. On the other end of the debate is how fast the oil will become rancid (definitely harming the flavor and nutrition) at room temperature. Most oils will eventually go rancid—especially at very warm room temperatures. In general, buy small amounts of oils, especially the most finely flavored or costly ones, from a store that has a rapid turnover. Store them in a cool, dark place, and use them promptly. In very hot or humid conditions, store oils in the refrigerator. Important note: Any fresh herbs or vegetables packed in oil should always be refrigerated, as the oil seals the air away from the moist material, creating the perfect conditions for cultivating botulism.