The 2012 ASHS Annual Conference

Fresh tomato fruit are chilling sensitive, but their sensitivity has been reported to decrease as they ripen. Modified atmosphere packaging (MAP) with reduced O₂ and elevated CO₂ slows the ripening process and has been found to reduce tomato chilling injury (CI) symptoms. Changes in the amounts of certain volatiles may be an indication of the occurrence of CI.  Some of these compounds have been reported to contribute to the fresh tomato aroma. For some other fruits, 6-methyl-5-hepten-2-one (MHO), which gives a fruity/floral aroma, has been found to remain stable or decrease during storage at ambient temperatures and decrease at lower temperatures. In this study, pink ripeness stage tomatoes were stored in MAP at 12.5 (the reported chilling threshold temperature), 15 or 18 °C for 20 days. Gas exchange was allowed through microporous films covering three different sizes of holes on the containers. CO₂ was injected into the packages immediately after sealing to establish 3% to 10% CO₂ (expected equilibrium concentrations). Measurements of gas concentrations were made every 2 days and homogenized tissue samples for volatile identification were taken and stored in the freezer at the same time. Aroma volatiles were identified by GC-MS using SPME headspace analysis. Several volatile compounds were found to change during the storage period. The amount of total volatiles decreased during 20 days of storage in all treatments. Total aldehydes increased in fruit that were stored at 18 °C for 20 days, but at 12.5 °C aldehyde levels did not change for both MAP and air treatments. Also, total aldehydes as a percentage of total volatiles was higher in fruit stored in air than in MAP. MHO as a percentage of total aroma volatiles was higher in fruit stored in air than in MAP, but was unaffected by storage temperature. Thus, MAP did not overcome aroma loss in tomatoes during low temperature storage. Further studies should address recovery of aroma volatile synthesis in low temperature MAP-stored tomatoes upon transfer to air at higher temperature.