Research Terms
Treating lettuce with a natural compound reduces the development of pink-rib discoloration. Lettuce is a commercially important crop, producing approximately 27 million tons globally in 2022 and accounting for nearly one-fifth of the $21.8 billion growers received in cash receipts from sales in the United States. Pink rib discoloration is one of the most common physiological disorders in lettuce, manifesting as pink discoloration of the midrib, leading to a loss of quality, visual appeal, and minimal marketability. Pink rib develops on several lettuce types, such as butterhead, iceberg, and romaine. This disorder develops pre- and postharvest in response to stressors, including high field temperatures, over-irrigation, harvesting over-mature heads, mechanical damage, and high-temperature storage conditions. Due to the irreversible damage and difficulty in controlling pink rib, it is a severe problem for both whole-head and fresh-cut salad lettuce shippers and producers.
Several strategies aim to attenuate the development of pink rib, such as modified atmosphere packaging, heat shock and anaerobic treatments, and exogenous chemical treatments. However, these only result in a slight to moderate reduction of the condition. Applying natural products such as L-cysteine, serotonin, or melatonin to other crops has had varying effects in treating discoloration disorders; the potential inhibitory effects of melatonin on pink rib in lettuce was unknown. Despite advances in crop discoloration research, suitable methods for potent, effective, consistent, and predictable inhibition of prink discoloration are scarce.
Researchers at the University of Florida have developed a natural compound treatment to reduce the development of pink rib discoloration in lettuce. This treatment involves rinsing wounded lettuce midribs with small concentrations of melatonin, delaying the onset and reducing the intensity of pink rib discoloration. It is a practical solution to reduce the percentage of unsellable lettuce.
Treatment of lettuce with melatonin to delay the onset or reduce the appearance of pink rib discoloration
This treatment involves rinsing lettuce with a low dose of melatonin to delay the development of pink-rib disorder in lettuce prior to commercial handling operations at temperatures of 2 to 5°C (36 to 41°F) and a relative humidity between 95 to 98%. This strategy delays or reduces pink-rib discoloration for up to five days.
