https://www.dailymail.co.uk/sciencetech/article-13890149/Scientists-extract-DNA-worlds-oldest-cheese.html

Around two decades ago, a team of archaeologists discovered mysterious white substances smeared on the heads and necks of several mummies found in the Xiaohe cemetery in Northwestern China's Tarim Basin. These mummies dated back to about 3,300 to 3,600 years ago, from the Bronze Age. At the time, scientists thought these substances might be a type of fermented dairy product, but they couldn't identify exactly what kind. Now, using advanced DNA analysis, researchers have finally unravelled the mystery. They identified cow and goat DNA in the cheese samples, and confirmed the white substances were in fact kefir cheese.

The samples from three different tombs contained species of bacteria and fungi including Lactobacillus kefiranofaciens and Pichia kudriavzevii - both commonly found in present-day kefir grains.