Heat Treatment Alleviation of Chilling-induced Suppression of Aroma Volatile Levels

Chilling exposure of tomatoes to 5 degrees C for longer than six to eight days can cause surface pitting, irregular (blotchy) color development and other symptoms of chilling injury (CI). The objectives for this study were to investigate whether a four-day exposure of tomato fruit to 5 degrees C chilling temperature at the mature green stage of development would impact flavor quality after ripening, and if a pre-chilling heat treatment could alleviate the internal CI. Mature green 'FL 47' tomatoes were gassed with ethylene and then divided into the following four treatments: 1) heat treated in 52 degrees C hot water for five minutes, then exposed to 5 degrees C for four days before being transferred to 20 degrees C; 2) heat treated then placed directly at 20 degrees C without chilling; 3) chilled at 5 degrees C for four days then transferred to 20 degrees C without prior heat treatment; and 4) untreated control, stored and ripened at 20 degrees C. All samples were held at 20 degrees C until ripened. Fruit were analyzed at the red-ripe stage for volatile components and submitted to a sensory panel for aroma evaluation. Results showed that chilling treatment generally suppressed production of aldehyde, alcohol, ketone, ester, sulfur, and terpene volatile compounds, including the following abundant and/or important volatiles: hexanal, 6-methyl-5-hepten-2-one, beta-ionone, 2-methylbutanal, 2-phenylethanol, guaiacol and 2-isobutylthiazole. Heat treatment alone did not affect most volatile levels after ripening. Heat treatment prior to chilling alleviated the reduction of volatile compounds caused by chilling exposure, which agreed with the sensory panel results in that panelists found that "heating + chilling" treated fruit had greater "tomato odor" than fruit that were chilled only.