Volatile compounds contribute to carrot (Daucus carota) flavor. However, effects of postharvest treatments on these compounds are not defined. To characterize treatment effects, fresh carrots (cv. Sunrise) were treated with 0 or 1.0 μL/L 1-methylcyclopropene (1-MCP) at 10 °C for 16 h, then exposed to 0, 0.3, or 1.0 μL/L ozone (O3) at 10 °C for 1, 2, or 4 days, and subsequently stored at 0 °C for up to 24 weeks. Twelve terpenes were identified in the headspace over whole carrots, including dimethylstyrene (22.5%), alpha-pinene (19.1%), caryophyllene (15.8%), beta-pinene (9.1%), p-cymene (8.3%), limonene (7.7%), gamma-terpinene (6.7%), myrcene (4.7%), gamma-terpinolene (4.5%) camphene (1.0%), alpha-phellandrene (0.52%), and sabinene (0.03%). Most terpenes responded similarly to treatments and storage. Immediately after treatment with 1.0 μL/L O3 for 1, 2, or 4 days, total terpene concentrations were 45%, 85%, and 87% greater than concentrations in non-treated controls. Caryophyllene, beta-pinene, and sabinene did not increase in response to the O3 treatment unlike the other terpenes. 1-MCP reduced terpene concentrations by an average of 18%. O3 treatments also stimulated stress volatile production. Ethanol headspace concentrations were 8-, 21-, and 43-times greater than the nontreated controls immediately following treatments with 0.3 nL/L O3 for 4 days or 1.0 μL/L O3 for 2 or 4 days, respectively. However, after 8 weeks, no differences among treatments were observed. Hexanal production also was stimulated by all O3 treatments, being 2- to 11-times greater than controls immediately following treatment. 1-MCP reduced O3-stimulated ethanol and hexanal production by 23% and 8%, respectively.
Effects of 1-MCP and Ozone on Carrot Volatiles during Storage
