Antioxidant activity and sensory attributes of tomatoes dehydrated by combination of microwave and convective heating

Tomato halves were dried in a combined microwave-hot air system. Drying experiments were carried out by applying the microwave energy (0.5 W/g) at the beginning of the dehydration process (for 2 and 3.5 hours); simultaneously combining microwave (0.25 W/g) with convective hot-air drying (70°C); and by applying only convective hot air at 70°C. The combined microwave-hot air heating reduced significantly the drying time (up to 50 %), if compared with the only convective system. Simultaneous convective and microwave heating allowed besting preserving antioxidant activity of dried tomatoes, by minimizing lycopene and phenols losses, while ensuring satisfied texture characteristics and less percentage shrinkage. Moreover, the same samples better preserved the colour characteristics of fresh tomato.