The mummies were buried with clumps of cheese, presumably a snack for them to enjoy in the afterlife.
This particular cheese was simple to make, nutritious and easily digestible, researchers said in a paper published in the Journal of Archaeological Science.
They unearthed the cheese during excavations of the Xiaohe Cemetery, also known as Ordek's necropolis, between 2002 and 2004, 'LiveScience' reported.
The ancient necropolis was first discovered in a sand dune located by a dried-up riverbed in 1934. It contains hundreds of mummies buried in large, wooden coffins that resembled upside-down boats, which were then covered with cowhide that sealed the coffins from the air.
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A chemical analysis found that the ancient dairy product didn't require an enzyme, known as rennet, which is found in the guts of ruminants and is used to make hard cheeses such as cheddar.
Instead, makers likely fermented this cheese using microbes such as Lactobacillus and Saccharomycetaceae yeasts, which are commonly used to make a still-popular fermented dairy beverage known as kefir.
The team also made their own homemade kefir, and found that the chemical and bacterial composition matched the snacks buried with the mummies.