Researchers have stumbled upon the earliest evidence of beer brewing in China from a 5,000-year-old recipe discovered in residue on pottery at an archaeological site. The evidence reveals an "advanced beer brewing technique" with elements from both the East and West.

The team pinpointed the recipe through the examination of yellowish residue that was obtained from pottery funnels and wide-mouthed pots which contained traces of ingredients - broomcorn millet, barley, a chewy grain known as Job's tears, and tubers - that had been fermented together.

"The discovery of barley is a surprise," said Jiajing Wang of Stanford University and lead author of the study, who suggests that it is the earliest evidence of barley in Chinese archaeological remnants. "This beer recipe indicates a mix of Chinese and Western traditions - barley from the West; millet, Job's tears and tubers from China."

The recipe suggests that barley entered China approximately 1,000 years earlier than previously believed and "may have been used as a beer-making ingredient long before it became an agricultural staple."

The recipe was discovered at Mijiaya, located near a lake connected to the Wei River in northern China. The region contains numerous artifacts that point to the presence of beer brewing, filtration and underground storage between the years 3,400 BC and 2,900 BC.

Despite the wealth of materials and the discovery of the recipe, the proportions of the ingredients are not known, making it hard for researchers to determine what the ancient beer tasted like.

"My guess is that the beer might have tasted a bit sour and a bit sweet," Wang said. "Sour comes from fermented cereal grains, sweet from tubers."

Experts have also discovered evidence of beer brewing in Iran and Egypt that dates to approximately the same time period as the beer recipe in the current study.

"The introduction of Middle Eastern barley into a Chinese drink fits with the special role of fermented beverages in social interactions and as an exotic ingredient which would appeal to emerging elite individuals," said Patrick McGovern of the University of Pennsylvania, who was not involved with the study.

McGovern agrees that the beer brewing techniques in China were highly advanced and suggests that "ancient peoples, including those at Mijiaya, applied the same principles and techniques as brewers do today."

The findings were published May 23 in the Proceedings of the National Academy of Sciences.