Combining acetic acid and ethanol as an anti-browning treatment for lettuce butt discoloration through repression of the activity and expression of phenylalanine ammonia lyase

•Dipping cut surfaces in acetic acid & ethanol represses lettuce butt discoloration.•Four lettuce phenylalanine ammonia lyase (PAL) genes are wound-inducible.•Acetic acid transcriptionally suppresses these four wound-inducible PALs.•Addition of acetic acid inhibits PAL enzyme activity in vitro and in planta.•Ethanol strongly represses microbial growth and moderately inhibits browning.