FACTORS INFLUENCING ETHYLENE-INDUCED ISOCOUMARIN FORMATION AND INCREASED RESPIRATION IN CARROTS

Ethylene-induced formation of isocoumarin was characterized in relatio n to ethylene-enhanced respiration in whole or cut carrots (Daucus car ota L.), Ethylene concentrations (0.1 to 5 ppm) and temperatures (1 to 15C) that increased respiration also favored a more rapid formation o f isocoumarin droxy-3-methyl-6-methoxy-3,4-dihydro-isocoumarin), Expos ing mature carrots to 0.5 ppm C2H4 for 14 days at 1 or 5C resulted in isocoumarin contents of 20 and 40 mg/100 g peel, respectively, These l evels were easily detected as a bitter flavor in the intact carrot roo ts, Immature carrots formed higher levels of isocoumarin than mature c arrots; 180 mg/100 g peel were detected in young carrots stored 14 day s at 5C in air containing 0.5 ppm C2H4. Freshly harvested carrots expo sed to 5 ppm C2H4 accumulated I-fold higher isocoumarin levels than th ose formed by carrots stored 30 days at 5C before exposure to C2H4. An atmosphere of 100% O-2 potentiated the effect of C2H4 on isocoumarin formation, resulting in a 5-fold increase over that found in carrots t reated with C2H4 in air, A storage atmosphere of 0.5 ppm C2H4 in 1% O- 2 resulted in isocoumarin levels about one-half those attained in 0.5 ppm C2H4 in air, Sliced, cut, or dropped carrots exposed to C2H4 showe d greater isocoumarin accumulation rates than intact uninjured carrots , Peeled baby carrots, however, had little capacity to form isocoumari n, In general, the more rapid the respiratory rise in response to C2H4 , the more rapidly isocoumarin accumulated, The greater the respirator y response to ethylene, the higher the level of isocoumarin formed.