Drying kinetics of turmeric cubic particles under fluidized condition

Abstract

• This study is the first to report on the drying behavior and kinetics of cubic turmeric particles in a fully fluidized condition. • Fluidized bed drying significantly reduces moisture content to below 7.5% db (8.13% wb) within 4 hours at 60°C. • Drying at 40°C exhibited a constant-rate period while those at 50°C and 60°C transitioned directly to the falling-rate stage. • Effective diffusivity increases from 4.64×10⁻¹⁰ to 9.93×10⁻¹⁰ m²/s as temperature rises from 40°C to 60°C, with an activation energy of 32.33 kJ/mol. • Four- and five-degree polynomials and five thin-layer models fit the drying kinetics well (R² > 0.9, χ² < 0.001). Drying is a vital step in turmeric processing to extend shelf life and retain bioactive properties, color, and flavor for applications in the food, pharmaceutical, cosmetic, and textile industries. This study examined the drying kinetics of turmeric cubic particles in a fully fluidized bed at 40, 50, and 60°C. The results showed that temperature strongly influenced moisture reduction. At 60°C, the samples reached moisture content of 8.12% db (7.43% wb) in 4 h, versus 73.42% db (42.34% wb) at 40°C and 27.58% db (21.62% wb) at 50°C. Drying at 40°C featured an initial constant rate period owing to limited evaporation, whereas 50°C and 60°C skipped this period, shifting directly to diffusion-controlled drying. Effective moisture diffusivity increased with temperature, from 4.64×10 −10 m²/s at 40°C to 9.93×10 −10 m²/s at 60°C, following Arrhenius kinetics with an activation energy of 32.33 kJ/mol. Drying rates fitted four and five-degree polynomial models (R 2 = 0.94–0.99). Five thin layer models (Page, logarithmic, Henderson–Pabis, Two-term, and Midilli) excellently matched the moisture ratio data (R 2 >0.9, χ 2 <0.001). These results highlight fluidized bed drying at higher temperatures as efficient for shortening drying time and optimizing moisture removal in industrial turmeric processing. This study addresses a key gap in turmeric drying kinetics under fluidized conditions, aiding process control and commercialization.

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