Combined osmotic dehydration and drying process of pirarucu ( Arapaima gigas ) fillets

Abstract

The osmotic dehydration (OD) and complementary drying of pirarucu (Arapaima gigas) fillets were studied. Pieces of the dorsal portion of pirarucu (60 mm × 20 mm × 10 mm) underwent OD in a binary solution (NaCl-water) with the application of vacuum pulse following a central rotatable composite design. The effect of the following process variables was assessed: temperature (20–40 °C), osmotic solution concentration (15–25% NaCl), and vacuum pulse pressure (7–101 kPa) on water loss (WL), solid gain (SG), and water activity (a_w). OD kinetics was obtained and the Peleg model was fitted to WL and SG data. The osmotically dehydrated pirarucu was dried (40–70 °C) in a fixed-bed dryer and mathematical models were fitted to the drying data. The optimal operational condition for the OD process was 35 °C, solution with 25% NaCl, and atmospheric pressure, which yielded WL of 14.87 ± 1.46%, SG of 8.56 ± 0.45%, and a_w of 0.87 ± 0.02. The Peleg model efficiently predicted the WL and SG kinetics. The increase in the water loss in drying was more evident at low temperatures (40–50 °C) with effective diffusivity ranging from 10.85 × 10⁻⁹ to 12.30 × 10⁻⁹ m²/s. The Midilli and Page models efficiently predicted the drying kinetics.

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