Refractance Window Drying of Nutmeg Mace: Drying Kinetics and Quality Characteristics in Comparison with Hot-air Drying
Ann Annie Shaju
*
Department of Processing and Food Engineering, Kelappaji College of Agricultural Engineering and Food Technology, Kerala Agricultural University, Tavanur, Kerala, India.
M. Varghese Prince
Department of Processing and Food Engineering, Kelappaji College of Agricultural Engineering and Food Technology, Kerala Agricultural University, Tavanur, Kerala, India.
Vaisakh Venu
Department of Basic Engineering and Applied Sciences, Kelappaji College of Agricultural Engineering and Food Technology, Kerala Agricultural University, Tavanur, Kerala, India.
G. K. Rajesh
Department of Processing and Food Engineering, Kelappaji College of Agricultural Engineering and Food Technology, Kerala Agricultural University, Tavanur, Kerala, India.
K. P. Sudheer
Department of Agricultural Engineering, College of Agriculture, Kerala Agricultural University, Vellanikkara, Kerala, India.
Lilia Baby
Krishi Vigyan Kendra, Malappuram, Kerala, India.
*Author to whom correspondence should be addressed.
Abstract
This study investigated the drying kinetics, mass transfer characteristics and quality attributes of nutmeg mace (Myristica fragrans Houtt.) dried using Refractance window drying (RWD) in comparison with conventional hot-air drying (HAD). Refractance window drying exhibited faster moisture removal and a higher effective moisture diffusivity (4.76 × 10⁻⁸ m² s⁻¹) than hot-air drying (4.56 × 10⁻⁸ m² s⁻¹). Moisture removal under both drying conditions occurred predominantly in the falling-rate period. Among the thin-layer drying models evaluated, the logarithmic model provided the best fit to the experimental moisture ratio data for both RWD and HAD. In addition, RWD yielded dried nutmeg mace with lower water activity (0.50), superior retention of the characteristic red colour and higher total phenolic content (14.26) compared with hot-air drying. The findings demonstrate that refractance window drying is an effective low-temperature dehydration technique for improving drying efficiency and preserving quality attributes of high-value nutmeg mace.
Keywords: Refractance window drying, nutmeg mace, drying kinetics, effective moisture diffusivity, thin-layer modelling, hot-air drying