Modeling and Optimization of Vacuum-infrared Dryer Performance in Production Process of Tomato Compressed Tablet: Chemical Properties

In this study, optimum drying conditions of compressed tablet tomato under vacuum-infrared conditions were determined to produce tablet with appropriate chemical and qualitative properties. The content of lycopene, total phenol, vitamin C concentration, antioxidant activity as chemical properties and color indices ΔL*, Δa* and Δb* were studied as qualitative properties. Drying process of samples was performed at five levels of air temperature of the compartment 40, 50, 60, 70 and 80 °C and five vacuum pressures 20, 30, 40, 50 and 60 kPa. Statistical analysis of data and optimization of drying process were performed using response surface methodology. The results showed that in vacuum-infrared drying, as the temperature of the dryer chamber increased, the concentration of vitamin C and total phenol content of tomato tablet decreased and lycopene content and antioxidant activity of tomato tablet increased. Also, increasing temperature increased the difference between the color indices L* and a* and reduced the difference between the color index b* compared to fresh tomatoes. The optimum point the drying process of tomato tablet was obtained at 56 °C and vacuum pressure of 30 kPa. The reduction rates of vitamin C concentration, lycopene content, and total phenol content of dried tomato tablets in optimal condition were 54.3, 2.6 and 29.62 percent, respectively. Drying at lower temperature increased the model's desirability index obtained by response surface methodology.