A groundbreaking discovery in the Xinjiang Uygur region of northwestern China has unveiled a 3,600-year-old cheese sample found in an ancient tomb, captivating both scientists and food lovers alike. The sample, identified as kefir cheese, marks the oldest cheese ever unearthed, according to a study published in Cell (2024, DOI: 10.1016/j.cell.2024.08.008). Paul Kindstedt, a cheese historian and professor emeritus at the University of Vermont, commented on the remarkable find, describing the cheese as resulting from a “funky microbial coagulation.”
Though Kindstedt was not part of the research team, he offers insight into the significance of finding kefir cheese specifically within the tomb. His theory revolves around the unique biochemistry involved in its production.
Kefir cheese, known for its solid, mild flavor, is produced as a by-product of liquid kefir, a fermented milk drink commonly available in grocery stores today. This beverage is created through lactic acid fermentation of goat milk, facilitated by a specific microbe known as Lactobacillus kefiranofaciens.
“There’s lots of lactobacilli in cheeses and milk products,” Kindstedt explained to Newscripts, “but this one is unusual in that it produces an exopolysaccharide called glucogalactan. This compound consists of glucose and galactose in polymer form and creates sticky biofilms along with a polysaccharide matrix that traps both lactobacilli and yeasts like Saccharomyces.”
While many lactic acid bacteria ferment both glucose and galactose monomers into lactose, L. kefiranofaciens uniquely ferments only glucose, leaving galactose behind. Kindstedt noted that if sufficient yeast is present, the leftover galactose can be fermented, resulting in carbon dioxide and alcohol.
Historically, alcohol was a scarce resource on the Eurasian steppe, a region known for its challenging agricultural conditions and limited fermentable carbohydrates. This makes the production of alcoholic kefir beverages one of the few ways for locals to obtain alcohol. This raises an intriguing question for Kindstedt: “Were these pastoralists in Xinjiang deliberately making kefir cheese, or was it merely a by-product of the kefir beverage? That’s the funky question.”
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