Dehydration of Green Coconut Pulp Using Cast-Tape Drying and Air Fryer Methods

Dehydration extends the shelf life of fruit pulps by reducing water activity, thereby inhibiting microbial growth and undesirable reactions. It also facilitates storage and reduces costs by eliminating the need for refrigeration. This study investigated the drying of green coconut pulp using cast-tape drying (CTD) and air fryer (AF) methods for powder production, followed by physicochemical characterization. The following parameters were determined: temperature profile (CTD and AF), drying kinetics (AF), moisture content, water activity, color, hygroscopicity, bulk and tapped density, Hausner Ratio (HR), and Carr Index (CI). The drying time of the pulp using CTD was 22±1 minutes, with moisture content reduced from 9.12±1.11 g/g to 0.08±0.01 g/g and water activity to 0.247±0.002. During the first 8 minutes, the drying rate was constant, with temperatures ranging between 70 and 78 °C, when the heat supplied is used to evaporate free surface water. After this period, the pulp temperature increased to 90–93 °C, characterizing the falling rate period. In the AF method, the drying time was 150 minutes, reaching a final moisture content of 0.09±0.01 g/g and water activity of 0.445±0.005. A constant drying rate was observed up to the 20th minute (0.16±0.03 g/g·min), with temperatures ranging from 37 to 46 °C, followed by a gradual increase up to 66 °C. The powders presented a typical whitish-yellowish color of green coconut pulp. The CTD powder had a slightly darker color (L = 83.9±0.8; a = 2.4±0.2; b* = 21.3±1.0; C = 21.4±1.0; h° = 83.6±0.5) compared to the AF powder (L* = 87.3±1.2; a* = 1.8±0.1; b* = 25.7±1.3; C = 25.8±1.3; h° = 86.6±1.2), possibly due to the higher final temperatures. Hygroscopicity was 12.8 ± 0.5% for AF powder and 16.9±0.2% for CTD powder, indicating low hygroscopicity (<20%). Bulk and tapped densities were 0.32±0.01 g/mL and 0.34±0.01 g/mL for AF powder, and 0.33±0.01 g/mL and 0.44±0.01 g/mL for CTD powder, respectively. The AF powder exhibited excellent flowability (CI = 5.32; HR = 1.06), while the CTD powder showed acceptable flowability (CI = 24.42; HR = 1.32). In conclusion, the CTD process operates in a shorter time and produces powder with slightly darker color, low hygroscopicity, and acceptable flowability, making it a technically viable alternative to the prolonged drying time required by the air fryer method.