quality:corruption
Middle Ages

In the cooler climates of northern Europe, people could store butter longer before it spoiled. Scandinavia has the oldest tradition in Europe of butter export trade, dating at least to the 12th century. After the fall of Rome and through much of the Middle Ages, butter was a common food across most of Europe—but had a low reputation, and so was consumed principally by peasants. Butter slowly became more accepted by the upper class, notably when the Roman Catholic Church allowed its consumption during Lent from the early 16th century. Bread and butter became common fare among the middle class and the English, in particular, gained a reputation for their liberal use of melted butter as a sauce with meat and vegetables.

In antiquity, butter was used for fuel in lamps, as a substitute for oil. The Butter Tower of Rouen Cathedral was erected in the early 16th century when Archbishop Georges d'Amboise authorized the burning of butter during Lent, instead of oil, which was scarce at the time.

Across northern Europe, butter was sometimes packed into barrels (firkins) and buried in peat bogs, perhaps for years. Such " bog butter " would develop a strong flavor as it aged, but remain edible, in large part because of the cool, airless, antiseptic and acidic environment of a peat bog. Firkins of such buried butter are a common archaeological find in Ireland; the National Museum of Ireland – Archaeology has some containing "a grayish cheese-like substance, partially hardened, not much like butter, and quite free from putrefaction." The practice was most common in Ireland in the 11th–14th centuries; it ended entirely before the 19th century.