Drying of Cherry Tomatoes Using Forced Convection Solar Greenhouse in Association with Infrared Heating

Abstract

This research was aimed to compare the drying of preserve cherry tomatoes in forced convection solar greenhouse in two different systems: System 1, solar greenhouse installing ventilation fan; System 2, solar greenhouse installing ventilation fan and infrared heater fixed drying temperature at 45-60 °C. The two systems were compared to open sun drying. Drying rate, drying time, and product quality after drying including color, water activity, sweetness and specific energy consumption were investigated. The samples with average initial moisture content at 81.88 %d.b. were dried until the final moisture content reached the same level of the products in the market at 11- 25 % d. b. The results showed that the average drying rate in System 2 was the highest at 1. 173 kg/ h and took the shortest drying time at 12 hours, where specific energy consumption was 3. 47 kWh/ kg which was 68. 79% less than System 1, in a range of 0. 54- 0. 55. The water activities of both systems were less than 0. 6 and were also less than the one from open sun drying with statistical significance at P ≤0.05. Fungal growth, bacterial growth and microbial growth were not occurred at those water activity values, resulting in longer preservation. Sweetness values of all systems were in a range of 28. 33- 29. 50 % Brix and not different with statistical significance at P ≤0.05. The total color different ΔE comparing to before drying of preserve cherry tomatoes dried in System 2 was the least. The brightness values of the samples from all systems were in a range of 29.11-29.84. They were different from the beginning of the drying with statistical significance at P ≤0.05. The yellowness values of the samples from System 2 before and after drying were close.