Modified-atmosphere packaging of minimally processed "Lollo Rosso" (Lactuca sativa) - Phenolic metabolites and quality changes

The effect of modified-atmosphere packaging (MAP) on the amount of soluble phenolics in, and the visual appearance of, white, green and red tissues of minimally processed "Lollo Rosso" lettuce were evaluated. Minimal processing induced a two-fold increase in the amount of soluble phenylpropanoids in the midribs during storage in air at 5 degrees C. When the lettuce was stored in the presence of 2-3% O-2 and 12-14% CO2, this increase was not induced and no browning was observed. A particularly marked decrease in the amount of phenylpropanoids was observed in MAP-stored green and red tissues. The concentrations of flavonoids and anthocyanins did not change much in midribs and green tissues, while they were significantly degraded in red tissues under MAP conditions. MAP storage proved useful in the prevention of browning, the main cause of quality loss in minimally processed "Lollo Rosso" lettuce. However, MAP storage was not so beneficial for the preservation of the quality of red tissues and? in fact, their overall visual quality, texture, aroma and macroscopic breakdown under MAP conditions were worse than those of air-stored tissues.