So, I know butter was an important product of at least scandinavian peasants, it was exported, used to pay taxes, and at least allegedly in one case paid as a stipend for someone to go to university. But I've never quite understood how these large amounts of butter (sometimes measured in barrels) was made to last. Was it simply salted sufficiently? Was it simply expected that butter would go rancid? Or is there something I'm missing?
This isn't so much a historical question as a culinary one - butter goes rancid from the outside in.
So the answer is this: the butter was salted and kept in the coolest place available (cellar), and by virtue of it being in barrels, the outer layer might go rancid but if you scraped that off, you'd have fresh butter there.