Quality of cut lettuce treated by heat shock: prevention of enzymatic browning, repression of phenylalanine ammonia-lyase activity, and improvement on sensory evaluation during storage.

Stored cut lettuce gradually turns brown on the cut section after several days of storage, because cutting induces phenylalanine ammonia-lyase (PAL) activity, the biosynthesis of polyphenol is promoted, and the polyphenols are oxidized by polyphenol oxidase. Here, the effect of heat shock treatment at 50 degrees C for 90 s on the quality of cut lettuce during cold storage was examined. The heat shock treatment significantly repressed the induction of PAL activity and phenolics accumulation in cut lettuce during storage, and prevented the browning of cut lettuce.