Thermal properties of crystalline coconut sugar using differential scanning calorimetry for rotary dryer process design

Abstract

Crystalline coconut sugar is widely used in the food industry due to its natural sweetness and nutritional content. However, its amorphous nature, high hygroscopicity, and tendency to undergo thermal degradation pose major challenges in drying and storage processes. Understanding the thermal behaviour of crystalline coconut sugar is crucial for effective drying and the design of suitable equipment. This study employed Differential Scanning Calorimetry (DSC) to characterise the thermal transitions of crystalline coconut sugar. Thermal characterisation was performed using DSC, 30 – 300°C at 10 °C/min to determine the glass transition temperature (Tg), melting point (Tm), and enthalpy change (ΔH). The results indicated that the Tg of crystalline coconut sugar represents the lower temperature limit that should be avoided to prevent stickiness and caking during the drying process, ranging from 90 to 100°C, whereas Tm represents the upper temperature limit that must be considered to avoid caramelisation and degradation, ranging from 165 to 200°C. These findings provide a scientific basis for determining the optimal temperature range for rotary dryer operation, which lies between 60 and 80°C. The Gordon–Taylor model demonstrated high agreement between predicted and observed Tg values. The DSC thermal analysis in this study provides a scientific foundation for selecting process parameters such as temperature, residence time, and air flow rate. This study highlights the importance of DSC characterisation as a crucial step in linking material properties to engineering design, thereby ensuring product quality and process efficiency in the drying of crystalline coconut sugar.