ARS | Publication request: Effect of UV-B light on soluble phenolic content of various whole and fresh-cut vegetables

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2011
Publication Date: N/A

Technical Abstract: Activation of phenylalanine ammonia-lyase (PAL) and chalcone synthase through abiotic stress caused by UV-B light exposure is the basis of a novel value-added processing method that enhances the nutrient content of specialty crops by increasing the synthesis of secondary metabolites, including terpenes, polyphenolic compounds, and nitrogen-containing compounds. In this study whole and fresh-cut vegetables were exposed on both the top and bottom surfaces to each of four different total energy doses and bimodal peak UV-B light irradiances (107-1,936 mJ/cm2 and 19-32 mW/cm2, respectively) and then incubated at 15°C for 72 h to allow the activation of enzymes. Response to the treatment conditions was assessed in terms of total soluble phenolic contents (TSP) at different recommended storage condition for each specialty crop. Sample groups included whole vegetable and root crops (Cherry tomatoes, sweet potatoes, and six varieties of pigmented potatoes), and fresh-cut vegetables and root crops (Iceberg lettuce, broccoli florets and stems, husked white sweet corn, and sliced radish and daikon). Whole pink and red cherry tomatoes did not show a response to UV-B exposure after 4 and 11 days storage at 9ºC following incubation. Ama Rosa potatoes and yellow sweet potatoes exhibited an increasing TSP trend after 14 days storage at 15ºC while the other five potatoes varieties did not benefit by the UV-B treatments. Fresh-cut lettuce and broccoli floret showed significant 3.2 and 1.1 times increase, respectively, in TSP due to the combined effect of wounding and UV-B light exposure after 3 days storage at 5ºC following incubation. UV-B exposure did not affect TSP of husked white sweet corn, and sliced radish or daikon after incubation. Ultraviolet B light exposure can be used as an additional processing step on selected specialty crops to enhance their nutritional value. Industry Relevant Information: UV-B light exposure on selected fresh-cut vegetables can increase significantly phenolic compounds resulting in improved antioxidant capacity.