ISOCOUMARIN CONTENT OF CARROTS AS INFLUENCED BY ETHYLENE CONCENTRATION, STORAGE TEMPERATURE AND STRESS CONDITIONS
Bitterness in carrots has been shown to be induced by exposure to ethylene resulting in synthesis of 8-hydroxy-3-methyl-6-methoxy-3, 4-dihydroisocoumarin. Isocoumarin was extracted with hexane, purified by TLC or solvent partitioning, and determined spectrophotometrically. The rate of isocoumarin formation increased with increasing ethylene concentrations (0.5 to 50 ppm) and with increasing temperatures (0 to 15 C). No isocoumarin was detected in intact carrots stored in air. Exposure of carrots to 0.1 ppm ethylene at 5 C for 30 days resulted in little isocoumarin formation, whereas 0.5 ppm for 14 days induced over 20 mg/100 g peel, which could be easily detected sensorially. The isocoumarin contents of water stressed and unstressed whole carrots held for 30 days at 5 C under 0.5 ppm ethylene were similar. Sliced carrots held under the same conditions showed a marked increase in isocoumarin levels, reaching 120 mg/100 g peel. Even under air, sliced carrots formed low levels of isocoumarin. Different isocoumarin levels were found among the 13 carrot cultivars examined.
Lafuente, M.T., Cantwell, M., Yang, S.F. and Rubatzky, V. (1989). ISOCOUMARIN CONTENT OF CARROTS AS INFLUENCED BY ETHYLENE CONCENTRATION, STORAGE TEMPERATURE AND STRESS CONDITIONS. Acta Hortic. 258, 523-534