Refractance Window Drying of Pineapple Puree for the Preparation of Fruit Leather: Influence of Process Parameters on Drying Kinetics and Quality

Refractance window drying (RWD) is a fourth‐generation thin‐layer drying technique used for a variety of perishable foods. The objective of the present research work was to investigate the effect of drying temperature (50°C, 60°C, and 70°C) and puree thickness (2 and 4 mm) on the mass transfer and quality characteristics of RW‐dried pineapple leather and comparing it with that of puree obtained by freeze‐drying (FD). The findings exhibited that RWD of 4 mm thick pineapple puree at 70°C (RW 70–4 mm) significantly augmented the drying rate and moisture diffusivity ( D eff ) by 1.5–2.4 times and 54.29%–63.56%, respectively in comparison to the RWD at 50°C and 60°C. Furthermore, RWD enhanced the activation energy for 4 mm thick pineapple puree (46.63 kJ/mol) by approximately 25% when compared to the 2 mm thickness (46.63 kJ/mol). Page model with higher R 2 (0.9875–0.9987) and lower SSE (0.0011–0.0219) and RMSE (0.0131–0.0370) values displayed the best fit for predicting the drying behavior. RWD of 4 mm puree at 70°C indicated the least color change (Δ E = 9.57 ± 1.68) with L * value (63.09 ± 0.52) closer to that of the FD sample (71.64 ± 0.01). In comparison to drying at low temperatures (50°C, 60°C), RWD at 70°C preserved the content of total phenolic compounds (336.07–359.20 mg‐GAE/100 g), ascorbic acid (158.57–194.2 mg/100 g), and good retention of antioxidants (37.04%–38.77%) analogous to FD. RWD is an effective method for drying high moisture fruit puree in shorter duration than FD while retaining the quality attributes.