Quality Changes of Fresh-Cut Butterhead Lettuce under Sub- and Superatmospheric Oxygen Condition

The effects of controlled atmospheres (CA) containing 5 kPa O-2 and 0 kPa CO2, 5 kPa O-2 and 15 kPa CO2, 75 kPa O-2 and 0 kPa CO2, 75 kPa O-2 and 15 kPa CO2, and 21 kPa O-2 and 0 kPa CO2 (as control) on the respiration rates and visual appearance of fresh-cut butterhead lettuce (Lactuca sativa L. var. capitata L.) were studied. The fresh-cut lettuce was stored for 10 days at 7 degrees C. During the same period and the same gas conditions browning was quantified on the lettuce stems using L*, chroma and hue values. This method has been previously applied for lettuce being L* the best parameter related with enzymatic browning. CA did not show a clear influence on the respiration rates of fresh-cut lettuce. Elevated CO2 treatments decreased the browning on the lettuce stems. Color changes were also slightly delayed on the stems under high O-2 levels. CA with 5 kPa O-2 did not prevent browning. This O-2 level was probably high enough to allow enzymatic browning on the stems. At the end of storage, fresh-cut lettuce stored under superatmospheric (75 kPa) O-2 condition combined with 15 kPa CO2 had the best visual appearance reducing the enzymatic browning.