The effect of supplementary LED illumination of Romaine lettuce on midribs pinking after harvest

Yahya, M. H., Chadwick, M. J. and Wagstaff, C. ORCID: https://orcid.org/0000-0001-9400-8641 (2025) The effect of supplementary LED illumination of Romaine lettuce on midribs pinking after harvest. Journal of Horticultural Science and Biotechnology. ISSN 2380-4084 doi: 10.1080/14620316.2025.2519380

Abstract/Summary

Pinking of midribs is a major postharvest issue in cut lettuce. Here, the effects of cultivar, light intensity and time of storage on pinking discolouration and related metabolites were elucidated. Two cultivars of Romance lettuce, Keona (fast pinking) and Icarus (slow pinking) were grown under four light intensities (L1 – L4: 1044, 578, 386 and 338 µmol.m −2.s −1 respectively); we determined their effects on pinking of leaf midribs, phenolic acids, soluble sugars and total ascorbic acid concentrations after eight days of cold storage. Differences in pinking index of the midribs of the two cultivars were only observed when the plants were grown in higher light intensities. All phenolic acids increased during storage and were highest at L1. Keona consistently contained higher concentrations of glucose, galactose and sucrose regardless of light intensity compared with Icarus after both 0 days and 8 days of storage. Principal component analysis (PCA) shows that coumaric acid, caffeic acid, and chlorogenic acid were positively correlated with the pinking index for both cultivars. The study revealed that pinking was reduced when the plants were grown at a low light intensity. Using low pinking cultivars offers a clear benefit in improving postharvest quality, especially when plants are grown under high light intensity.