How did ancient people store food before refrigeration?

Refrigeration is a pretty new phenomenon, so for millennia, people had to find clever ways to preserve food. These practices slowed the growth of microorganisms that could cause foodborne illnesses or lead food to rot. Many preservation practices other than refrigeration — like salting, drying, smoking, pickling and fermenting — have been used for a long time. 

These methods aside, how did ancient people store their leftovers?

It turns out that early hunter-gatherers had some pretty creative ways to extend the "shelf life" of their larder.

Related: Does salt make water boil faster?

Fishing for mammoth

One fall morning in 2015, two farmers in Michigan made an unexpected discovery: a pelvis bone from a mammoth. After a few phone calls and an excavation, a research team uncovered additional paleontological and archaeological evidence that brought the scene into greater clarity.

More than 11,000 years ago, mammoth herds roamed North America. For hunter-gatherers, bringing down an animal the size of an African elephant would be like winning the lottery — a prize you don't want to lose. So, some Indigenous people put their mammoth leftovers into ponds to keep it for later use.

"The pond offers a place to stash carcass parts," Daniel Fisher, a professor and curator in the University of Michigan Museum of Paleontology, told Live Science. "What is the alternative when there are other predators and scavengers on the landscape who will gladly partake of a meal?"

The carcass was purposely placed in one of the many small, shallow ponds that dot the postglacial landscape of the Upper Midwest. But the meat's preservation wasn't due to the water, exactly; it was largely the hard work of the bacteria, Lactobacilli, that live in the water. 

Lactobacilli produce lactic acid, a chemical byproduct of anaerobic respiration. The bacteria colonize the meat, and the lactic acid preserves the muscle mass. Fisher also credited the low temperature and the low oxygen content of the lake water in aiding the preservation process. 

Fisher believes the hunt probably occurred in the autumn. Felled animals were butchered where they died, and large pieces were deposited in the water in nearby small ponds. The meat remained edible until the following summer. Fisher knows this because he has conducted experiments using deer, lamb and even horse. He found that the meat was still edible (after cooking it first to kill any harmful bacteria that might have taken up residence in the meat), even after spending months submerged in similar small, cold ponds. 

"The lactic acid also tenderizes the meat," Fisher said. "It does impart a strong odor and taste, like Limburger cheese. It makes an interesting meal."

Pass the bog butter and jam

Keeping food cool makes sense, but not everyone had a lake in their backyard. Burying food is another ingenious way to keep food fresh. Burial shields food from sunlight, heat and oxygen, all of which increase the rate at which food spoils.

Bogs offer an intriguing burial option. A bog is a freshwater wetland of soft, spongy ground consisting mainly of partially decayed plant matter, called peat. The cool, low-oxygen, highly acidic environment is perfect for preserving perishable foods.

Related: Why does mint make your mouth feel cool?

In Northern Europe, ancient civilizations would put food, including butter, into the bog to preserve it. Archaeologists have pulled wads of a waxy, paraffin-like substance from the waterlogged muck. Researchers performed chemical analyses on the waxy substance and identified it as a dairy product, giving it the fun alliterative name "bog butter." 

"Within two or three years, the fat in the fresh butter degrades into constituent components," said Jessica Smyth, an assistant professor in the University College Dublin School of Archaeology who published a 2019 study on bog butter in the journal Nature. "You have a lump of fatty acids."

Bogs offered early agricultural communities a way to preserve perishable foods, like dairy products, for a longer period. According to Smyth, there are ethnographic mentions of people burying their summer butter in bogs for storage. The curated butter is edible, but it may take on the tangy flavors of the surrounding peat that is an acquired taste. 

"It is easy to look at bog butter as an anomaly or freak event, but it was probably a common practice," Smyth told Live Science. "The peatlands are providing a window into prehistoric agricultural practices that have vanished from the world."

Originally published on Live Science.