The effect of surface chemistry on the caking behaviour of sucrose crystals

The caking behaviour of organic crystals presents a significant challenge in both the food and pharmaceutical industries. This study aimed to investigate how surface impurities influence the caking behaviour of sucrose (sugar) crystals. Sucrose crystals were selected as the model material due to their relevance in various industries such as food processing and pharmaceuticals. The impact of surface chemistry was assessed for sucrose crystals with varying levels of impurities, namely white sugar, light brown sugar, and dark brown sugar. These crystals were subjected to controlled cycles of humidity exposure, compaction, and drying to induce caking, simulating real-world scenarios. The caking propensity was evaluated using a compression test, while the surface chemistry was characterized through Inverse Gas Chromatography (IGC). Moisture sorption properties were evaluated using a Dynamic Vapor Sorption (DVS) technique, and the formation of solid bridges was studied using scanning electron microscopy (SEM) and X-ray tomography. The results indicate that impurities play a crucial role in enhancing the caking behaviour of sucrose crystals by influencing their hygroscopicity and facilitating solid bridge formation. This study provides valuable insights into the relationship between surface chemistry, moisture sorption properties, and the caking behaviour of sucrose crystals, offering strategies to mitigate caking issues. • Sucrose crystals with varying impurities, as the model materials, were studied for caking behaviour. • White, light brown, and dark brown sugar granules underwent controlled humidity, compaction, and drying cycles. • Surface chemistry analysed using IGC and FTIR techniques; cake formation studied using compression tests and X-ray tomography. • Findings indicate that impurities enhance caking by increasing hygroscopicity and promoting solid bridge formation.