Effect of cyclic exposure to ozone gas on physicochemical, sensorial and microbial quality of whole and sliced tomatoes

The effect of a humidified flow of ozone-enriched air applied cyclically (4 +/- 0.5 mu L L-1 Of O-3 for 30 min every 3 h) on metabolic behaviour and sensorial and microbial quality of whole and fresh-cut 'Thomas' tomatoes stored up to 15 days at 5 degrees C was examined. The application of O-3 initially stimulated the respiration rate in a way similar to a stress, although after 2 days, the metabolic activity decreased to a rate lower than that of control (air flow). In O-3-treated whole and sliced tomatoes a higher sugar (fructose and glucose) and organic acid (ascorbic and fumaric) content was found. The kind of cut (whole or slices) did not affect the sensitivity of tomato to O-3. In whole tomatoes, O-3 maintained the tissue firmer than in control fruit while no influence was found on slices. The O-3 treated fruit retained a good appearance and overall quality in slices but experienced a reduced aroma. Also, O-3 substantially reduced microbial counts, being more noticeable on bacteria (1.1-1.2 log(10) units) than on fungi (0.5 log(10) units). This effect was higher when the storage time was longer and when a higher O-3 level (7 mu L L-1) was used. O-3 did not cause any damage or off-flavour in slices or whole tomatoes. In conclusion, the assayed O-3 treatment can be useful for maintaining quality and reducing microbial populations in whole and sliced tomato. (c) 2005 Elsevier B.V. All rights reserved.