Effect of ozone and calcium lactate treatments on browning and texture properties of fresh-cut lettuce

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.