Butter, like all fats, is a vehicle for flavor and will easily pick up other odors. It can also quickly become rancid. Butter should always be stored away from highly aromatic foods. Heat and light can also cause undesirable chemical and physical changes in butter. Leaving butter unrefrigerated can result in flavor changes, rancidity, and mold growth, which affect the texture and can give the butter a distinctive smell—stale, cheesy, or decomposed. Bring out only the amount of butter that you plan to use for each recipe. After measuring what you need, any remaining butter should be covered or rewrapped and returned to the refrigerator immediately.