Abstract: A method of preventing wound-induced browning in lettuce by applying a short thermal stress induced by immersing the lettuce in water at approximately 40.degree. C. to approximately 60.degree. C. for approximately 360 seconds or less. Alternatively, forced-air heating could be used if the air was at a relative humidity of near 100% to prevent water loss. After heat-shocking the lettuce, the lettuce can be vacuum cooled to effectively cool and dry the lettuce. The heat-shock effect is so persistent that lettuce will not show any browning even after being held for approximately 15 days in the air at 5.degree. C. This treatment could eliminate the need to store fresh-cut lettuce in low oxygen, and or high carbon dioxide modified atmospheres to prevent browning during marketing. It would also allow the use of vacuum cooling to cool the processed lettuce. It would also prevent browning of cored, whole heads of lettuce.