On June 22nd, 2016 we learned about

Bog butter born from bacteria-free centuries in a swamp

It’s great trying new foods, expanding your culinary horizons, and maybe discovering a new favorite dish. Trying old food, on the other hand, might not be such a great idea, if only to avoid destroying something archaeological value. The food in question here is actually 22 pounds of butter, dating back 2,000 years that was dug out of a peat bog in Ireland. Weirdly, ancient hunks of butter aren’t actually that strange, as the practice of burying ‘bog butter’ was once fairly widespread across Ireland and Scotland, at least for those fortunate enough to have the dairy to do so.

Dairy as delicious as the day it was buried

Bog butter started as normal butter made of unsalted cow’s milk, possibly filtered through local materials like old cloth or a nest of grass. These items might add a bit of bacteria to the recipe to help the butter sour, but when it was ready to be buried there was no real secret ingredient involved. Bog butter was usually then wrapped some kind of container, most often a wooden bucket made expressly for the task. It was then buried in a peat bog for later retrieval at which point it would be remarkably unchanged, even thousands of years later.

The oldest bog butter that’s been found so far was a 100 pound blob dating back close to 5,000 years. It was noted for smelling like butter, but also for having taken on a more waxy consistency. Modern recreations of bog butter have found that with a year of underground preservation, the butter does absorb some flavor from its surroundings, being noted for a ‘gamey,’ ‘pungent,’ and ‘salami’ character. Overall though, it was well preserved thanks to the chemistry of the peat bog, which staved off bacterial rot with a combination of acidity and low oxygen levels. There’s a chance some people produced bog butter for its novel flavor, but it also seems likely that this process was the easiest way to preserve what was once a precious resource.

Made for caloric and monetary value

Butter was more than a tasty source of calories to those that would bury the stuff. It could offer utility if used as a waterproofing agent on cloth, or be used as fuel for fires. It was even used a bit like currency for a time, with rent payments being recorded in quantities of butter instead of coins. So the 22 pounds of butter that was recently discovered may have once been intended as a nest egg if it wasn’t meant to be eaten first. In some cases, bog butter has been found without retrievable containers, which has suggested that it was occasionally sacrificed as an offering to gods or spirits as well, with no intention of recovery.

Bog butter isn’t the only food to have been preserved in the dirt of course. Some lumps of bog butter have turned out to be preserved animal tallow. Century eggs were created in alkaline mud in China. Cabbage was buried to preserve it, or produce sauerkraut. One the more volatile end of the menu, Nordic peoples buried salted salmon to ferment as gravlax. So the next time you discover something rotting at the back of your refrigerator, maybe consider if the problem with your food storage is that your leftovers are just too accessible, to you and to bacteria.


My second grader said: I don’t want to eat that. Please don’t make me eat that.

Not to worry. Most of this butter belongs in a museum, and nobody really advocates for eating the truly ancient samples.

Source: A Brief History of Bog Butter by Jason Daley, Smithsonian Magazine

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