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The effects of three treatments, 1 mg L −1 ozone at 18-20 • C, 15 g L −1 calcium lactate (CLac) at 50 • C and a combination thereof, were compared on fresh-cut lettuce over 10 days of refrigerated storage. Respiration rate, browning and texture were examined as main quality indicators. The use of ozone produced a significantly (P < 0.05) higher oxygen decline than the use of CLac (from day 3 to day 10). At the end of storage, CLac (alone or combined with ozone) samples had higher oxygen content (∼9%) than ozone samples (∼6%). Enzymatic activity decreased significantly (P < 0.05) in ozone samples. Polyphenol oxidase activity in fresh-cut lettuce treated with ozone (alone or combined with CLac) showed lower values on day 1 (<2500 units g −1 ) and at the end of storage (<3000 units g −1 ) than CLac samples (4000-4800 units g −1 ). Ozone also reduced peroxidase activity to ∼300 units g −1 after treatment. Finally, pectin methylesterase activity was also reduced with ozone, showing a negative effect on textural properties. Data suggested that CLac maintained quality markers better than treatments with ozone and ozone/CLac combination over 10 days of storage. INTRODUCTIONConsumers increasingly require food products that preserve their nutritional value, retain a natural and fresh colour, flavour and texture and contain fewer additives such as preservatives. 1 Recent research has underlined the importance of fruit and vegetable consumption to health and has reported new techniques to preserve the nutritional and sensory qualities demanded by consumers.Even though fresh-cut produce has been sold since the 1940s, the quality is unpredictable and the shelf life limited. The extension of quality retention for fresh-cut products is relevant for the industry owing to its economic impact. It is important that the washing treatments applied to fresh vegetables help maintain their quality, since consumers demand a fresh product as well as convenience and long shelf life. 2 Tissue browning is one of the major causes of loss of quality of fresh-cut vegetables. Browning is influenced by the concentration of phenolic compounds and by other factors such as the activity of polyphenol oxidase and peroxidase enzymes. Wound-induced loss of cellular compartmentalisation of phenolic compounds (mainly in the vacuole) and polyphenol oxidase (in the cytoplasm) results in tissue browning at a rate that increases with temperature and water loss. 3 The other cause of quality loss is decrease in firmness.