Image copyright Jiajing Wang Image caption Archaeologists were able to work out the pottery was used to brew beer from analysis of the residue found on it

Chinese drinkers may have been brewing beer as many as 5,000 years ago, new research suggests.

US and Chinese researchers say they found traces of barley, millet, grain, and tubers used in fermentation.

It was found on pottery discovered in Shaanxi province in northern China during an archaeological dig 10 years ago.

It would be the earliest known instance of beer-making in China and suggest a sophisticated approach.

Published in the US Proceedings of the National Academy of Sciences, the study also suggested that barley may have been used for booze before being used for food.

The findings suggest that drinkers in China first began to develop a taste for beer around the same time as people in ancient Egypt and Iran - from where the barley may have come.

Image copyright Jiajing Wang Image caption As every home-brewer knows, funnels are an essential piece of kit

The pottery fragments were originally found in an archaeological dig in 2004-2006, but only had their residue analysed by Stanford University researchers in late 2015, confirming earlier speculation by Chinese scholars that they might have been used for brewing.

The find included pots and pottery funnels, covered with a residue of broomcorn millet, barley, a chewy grain known as Job's tears, and tubers.

It also included stoves that could have been used to heat and mash grains, as well as underground spaces that would have kept the brew at a cool, consistent fermentation temperature - and helped stop it going off quickly once it was made.

Image copyright Reuters Image caption While the scale has changed, the basic recipe for beer remains much as it was 5,000 years ago

"The discovery of barley is a surprise," lead author Jiajing Wang of Stanford University told the BBC in an email, as it was previously thought the grain arrived in China 1,000 years later.

"This beer recipe indicates a mix of Chinese and Western traditions - barley from the West; millet, Job's tears and tubers from China."

The exact taste of the ancient brew will remain a mystery however, as while the scientists say they know what ingredients were used, they don't know the quantities.