ABSTRACT Tomato is a heat‐sensitive and perishable crop that requires gentle drying techniques to preserve its quality and shelf‐life. One of the major challenges in drying such products is maintaining nutritional value while reducing energy consumption. In the present study, a Refractance Window (RW) dryer integrated with UV‐C irradiation and a heat pump was developed and evaluated for drying tomato slices. The effects of drying water temperature (60°C, 70°C, and 80°C) and slice thickness (2, 4, and 6 mm) on drying time, energy and exergy performance, lycopene retention, and microbial safety were investigated. A factorial experiment based on a randomized complete block design was conducted under two conditions: with and without heat pump integration. Results showed that incorporating the heat pump significantly reduced drying time and specific energy consumption (SEC), while improving exergy efficiency. At 80°C, moisture ratio reached 0.10 after 120 min with the heat pump, compared to 0.25 at 60°C without it. SEC was reduced by up to 30%, and exergy efficiency increased from 5.4% to 10.4% as temperature increased from 60°C to 80°C. Lycopene retention was highest (42.62 mg/kg) at 60°C and 6 mm slice thickness, indicating better nutritional preservation under milder thermal conditions. Microbial count dropped below 1.5 log CFU/g under UV‐C and heat pump conditions at 80°C and 2 mm thickness, without compromising product appearance. The optimal condition based on minimal SEC, maximum lycopene retention, and microbial safety was achieved at 70°C and 4 mm slice thickness.
Rezvani et al. (Fri,) studied this question.