Concentration and retention of ascorbic acid, carotenoids, and sugars in fresh-cut lettuce in modified atmosphere packaging

Fresh-cut lettuce is widely used in ready-to-eat salads sold in modified atmosphere packages (MAP). Even in MAP, fresh-cut lettuce has short shelf life that results in loss of nutrients. Lettuce cultivars exhibit genetic variation for shelf life in MAP, but their variation for nutrient retention is not known. Fifty accessions were evaluated for initial content of ascorbic acid (AsA), carotenoids, and sugars and their retention in storage. Accessions with high content and/or good retention of one or more nutrients were identified. The romaine accession ‘Floricos’ had high levels of all the three nutrients. Accessions with relatively high retention of all the three nutrients were ‘Salinas 88’, ‘Siskiyou’, ‘Solar’, SM09A, ‘Romance’, and ‘Green Towers’. Romaine cultivars, ‘Balady Barrage’, ‘Green Towers’, and ‘Darkland’ had relatively high initial levels of all tested nutrients and good rate of their retention. There was no clear correlation between initial AsA/carotene concentrations and their retention rates, suggesting that besides content, retention of nutrients should also be a breeding target in a lettuce nutritional improvement program. Statistical analyses with the Pearson's correlation coefficient determined a negative relationship between tissue deterioration (AUDePS) and retention of all tested nutrients [r of −0.52 (P < 0.0001) for AsA, −0.27 (P < 0.01) for total carotene, and −0.59 (P < 0.0001) for total sugars], suggesting that an increase in tissue deterioration intensifies nutrient decay. Broad-sense heritability (H2) across the experiments was 0.15 for AsA, 0.23 for total carotene, and 0.50 for total sugars. Identification of germplasm with high nutrient content, extended shelf life and good nutrient retention provides valuable information for the lettuce industry and associated breeding programs.