Optimization of process conditions for moisture ratio and effective moisture diffusivity of tomato during convective hot‐air drying using response surface methodology

Abstract

This study was carried out to understand the moisture transfer behavior of tomato fruits subjected to pre-drying and drying processes. Effects of variety and process conditions on the moisture ratio (MR) and effective moisture diffusivity (Deff) of tomato were investigated using three-level-four-variable Box–Behnken design of response surface methodology (RSM). The experiment involved three varieties of tomato (Hausa, Tiwantiwa, and Roma VFN) and the process conditions include slice thickness (5, 7.5, and 10 mm), pre-drying treatment (ethyl acetate, NaCl, MgCl2∙6H2O and Na2S2O5, and honey and sugar solutions), and inlet air temperature (45, 55, and 65 °C). Results show that variety and process conditions influenced MR and Deff of tomato (p ≤ .05). Furthermore, quadratic model best described the moisture transfer behavior of tomato in convective hot-air dryer with R2 values of 0.8538 and 0.7150 for MR and Deff, respectively. Based on the aforementioned process conditions, optimum conditions achieved were Tiwantiwa variety, 5 mm slice thickness, pre-drying treatment in ethyl acetate solution, and inlet air temperature of 65 °C. With predictions of 0.774 and 2.844 × 10–8 m2/s for MR and Deff, respectively, and obtained desirability function of 0.771. Practical applications Tomato fruits has abundant health and economic benefits but remains highly perishable after harvest. Drying helps in reducing the wastage in most developing economies. It is applicable in the extraction of antioxidants (e.g., lycopene) in the production of dietary supplements and food additives. Dried tomato powder also has diverse applications generally at the household level and food industry. Proper knowledge of moisture transfer mechanism (e.g., effective moisture diffusivity) and factors influencing it during drying of tomato through optimization are right steps toward achievement of quality end products. This study provides information regarding the influence of variety and process conditions on moisture transfer during drying of tomato.