Pandanus amaryllifolius is a plant with aromatic leaves, which impart the characteristic flavour of aromatic rice. The quality of aromatic Pandanus leaves dried at low temperature (35 °C) and low RH (27%) in a heat pump dryer was evaluated and compared with those obtained from hot air drying at 45 °C. Thin-layer drying kinetics has been studied for both the conditions. To determine the kinetic parameters, the drying data were fitted to various semi-theoretical models. The goodness of fit was determined using the coefficient of determination, reduced chi square, and root mean square error. Aroma, colour, and overall acceptability determination of fresh and dried leaves were made using sensory evaluation. Drying of leaves took place mainly under the falling-rate period. The Page equation was found to be best among the proposed models to describe the thin-layer drying of Pandanus leaves with higher coefficient of determination. The effective moisture diffusivity values were also determined. The effect of low RH was prominent during the initial drying when the product was moist. The effect of temperature was prominent in the later part of drying, which acted as a driving force for moisture diffusion and hence the total drying time was reduced. Retention of aromatic compound 2-acetyl-1-pyrroline content was more in low temperature dried samples with higher sensory scores.
Keywords: 2-Acetyl-1-pyrroline; Drying kinetics; Effective moisture diffusivity; Pandanus amaryllifolius; Sensory quality; Thin-layer drying models.