SOUR is validvalid

sharp or biting to the taste [adj SOURER, SOUREST] : SOURLY [adv] / to make sour [v SOURED, SOURING, SOURS]

4,647 of 196,601 in NWL2023·also valid in CSW24

having an acid taste [adj SOURER, SOUREST, SOURLY] / to make sour [v -ED, -ING, -S]