Chinese researchers have discovered a 5,000-year-old beer recipe through residues in ancient Chinese pottery believed to be used for beer making.

The beer-making tool kits were unearthed in underground rooms in the archeological site in Mijiaya, near a tributary of the Wei River in northern China. The pits were believed to be constructed around 3,400 to 2,900 B.C.

When the researchers analyzed the pots and jugs, they discovered a yellowish residue suggesting that the potteries were used for beer making and storage. Ion chromatography of the pots revealed a 5,000-year-old beer recipe that consists of fermented mix of broomcorn millet, barley, Job's tears and tubers.

Their findings, published in the journal Proceedings of the National Academy of Sciences of the United States of America, suggests that people in China have already developed advanced beer-brewing technology by using specialized tools and creating favorable fermentation conditions around 5,000 years ago.

Business Insider reported that researchers also found a pottery stove in the dig site. These stoves were used to break down carbohydrates to sugar. Also, the underground locations of the ancient breweries were essential in the brewing process and storage of beers. Too much heat can potentially destroy enzymes responsible for the conversion of carbohydrates to sugar.

Researchers were baffled when they discovered barley in the fermented mix. Barley is known to arrive at China at a much later date. The researchers then suggest that Barley reached China during that time for the beer making process.

"Barley was one of the main ingredient[s] for beer brewing in other parts of the world, such as ancient Egypt. It is possible that when barley was introduced from Western Eurasia into the Central Plain of China, it came with the knowledge that the crop was a good ingredient for beer brewing. So it was not only the introduction of a new crop, but also the movement of knowledge associated with the crop," Jiajing Wang, an archaeologist from Stanford University and the lead author of the study, told NPR.

Researchers were unable to determine the exact taste of the 5,000-year-old beer recipe because they don't know the correct proportions of the ingredients, but they suggest that it might taste a bit sour and a bit sweet.