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Other genes were introduced to overproduce succinic acid.

Andrew Waterhouse, a wine chemist at the University of California, Davis, agreed, saying that finding succinic acid indicated that fermentation had taken place.

In the latest excavation, the archaeologists skipped the chemical scrub. This allowed researchers to extract four organic compounds present in the potsherds: citric acid, malic acid, succinic acid and tartaric acid.

This allowed researchers to extract four organic compounds present in the potsherds: citric acid, malic acid, succinic acid and tartaric acid.

University of Pennsylvania biomolecular archaeologist Patrick McGovern found evidence of tartaric acid, an indication of brewing involving the Eurasian grape, as well as three associated organic acids: malic, succinic and citric.