Untargeted volatolomic approach for the identification of sensory quality markers of fresh-cut iceberg lettuce stored in modified atmosphere packaging

Fresh-cut iceberg lettuce is appreciated by consumers for its nutritive properties, convenience, and ease of use. Producers are then pushed to preserve the quality of these products by using modified atmosphere packaging (MAP). In this study, the influence of passive MAP (air) or active MAP (1-5 % O2), on several quality attributes of fresh-cut iceberg lettuce samples was evaluated during storage time (from 3 to 14 d) at 4 degrees C. The respiration rate and the electrolyte leakage values of samples packaged in active MAP were higher than those of fresh-cut iceberg lettuce stored in the air, indicating stressful storage conditions. Inverse trends were observed for O-quinones content and browning index until the end of the storage period. Sensory analysis highlighted that active MAP has preserved the visual quality, limiting the browning of the cut surfaces. On the other hand, active MAP modified the sensory profile after 3 d at 4 degrees C, and samples scored below the marketability limit for both odor and off-odor. Finally, a volatile organic compound characterization by headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) allowed the identification of target molecules that could signal a decrease in food quality under different conditions. A total of 118 compounds were identified and, among them, ethyl alcohol and acetaldehyde were identified as the best quality markers for passive MAP and active MAP samples, respectively, while ethyl acetate could represent a good compromise to assess the quality of fresh-cut iceberg lettuce, regardless of MAP conditions.