Growing season climates affect quality of fresh-cut lettuce

• Lettuce crops were exposed to environmental conditions that affected quality after cutting.
• Growing season temperature (GST) contributed to quality changes of fresh-cut lettuce.
• Headspace gas composition varied with GST and impacted off-odors and browning.
• Fermentative metabolites reduced while cut edge browning was promoted when GST increased.

The objective of this study was to investigate if different growing season climates influenced the quality of fresh-cut lettuce. Different cultivars and harvests of iceberg and romaine lettuce grown over 26 months were processed and stored for 11 d in active modified atmosphere (MA) and then transferred to air for 24 h at 7 °C. Pearson correlation coefficients were established between different climatic factors and subjective and objective parameters related to quality loss. Growing season mean temperature (GST) and growing cycle influenced the quality characteristics of fresh-cut lettuce but the correlations between GST and quality characteristics were always higher than for growing cycle in both types of lettuce, iceberg and romaine. Winter growing season caused low oxygen (O2) and more significantly high carbon dioxide (CO2) that reduced enzymatic browning although it conferred off-odors. Respiration rate was significantly influenced by GST but only in fresh-cut romaine. Interestingly, off-odors and fermentative metabolites such as ethanol and acetaldehyde were significantly reduced in those months of higher GST. However, cut edge browning was significantly promoted, indicated by the reduction in hue angle as GST increased. These results identified that the mean temperature during cultivation was the climate variable that contributed most to quality loss of fresh-cut lettuce. Due to the strong impact of growing season climate, some changes in raw material specifications, packaging design and days of shelf life are recommended in order to assure the quality of fresh-cut lettuce during the whole year.

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