Synergy between hot water treatment and high temperature ethylene treatment in promoting antioxidants in mature-green tomatoes

摘要

Controlled postharvest stresses were used to induce the synthesis of antioxidants in tomato fruit. In this study, a hot-water (HW) treatment of 52 degrees C for 5 min promoted higher total oxygen radical absorbance capacity (ORAC) compared to fruit immersed in 25 degrees C water for 5 min. Whereas, ethylene treatment at high temperature, particularly at 35 degrees C for 24, 48 or 72 h, induced higher content of total phenolics and ferric reducing ability of plasma (FRAP) than fruit treated with ethylene at 20 or 30 degrees C. In combination, there was synergy between the treatments, and this was most notable by the increase of total phenolics in HW-treated tomatoes exposed to ethylene at 35 degrees C for 24, 48 or 72 h. There was also a significant increase of total ORAC in HW-treated fruit exposed to ethylene at 30 degrees C for 72 h or 35 degrees C for 24, 48 or 72 h. This increase in antioxidant capacity was observed in the hydrophilic fraction of HW-treated fruit exposed to ethylene at 30 degrees C for 72 h or 35 degrees C for 24 or 48 h and in the lipophilic fraction of HW-treated tomatoes exposed to ethylene at 35 degrees C for 24, 48 or 72 h. Moreover, The HW-treatment especially maintained the level of total carotenoids and ascorbic acid when exposed to ethylene at 30 degrees C for 72 h or 35 degrees C for 48 or 72 h. Nevertheless, the high temperature ethylene treatment reduced the a* value of tomato peel regardless of the application of HW treatment. In conclusion, application of a HW treatment of 52 degrees C for 5 min followed by exposure to ethylene at 35 degrees C for 48 h was most effective in synergistically improving the antioxidant capacity and composition of tomatoes without severely impairing color development.