Effects of sucrose particle size on the microstructure and bloom behavior of chocolate model systems

Model chocolates were developed by gradually replacing cocoa powder in the chocolate system (containing 54 g cocoa butter, 66 g cocoa powder, and 0.5 g lecithin) with sucrose with different D₉₀ particle sizes (25.0, 40.3, 61.5, 98.6, and 163.1 µm) by 15, 50, or 75% on a volume basis. Bloom extents were evaluated by changes in whiteness index (ΔWI) and white area percentage (WA%) while surface roughness was quantified using a new 4-neighborhood-pixels model. Reducing sucrose D₉₀ particle sizes at higher volume fraction levels significantly increased particle interactions (quantified by the sedimentation volume and Casson viscosity) and led to enhanced visual bloom and greater surface morphological changes, indicating that the microstructures in the chocolate matrix for fat migration and recrystallization had a significant impact on bloom during storage. Surface morphological characteristics such as increased pores and protrusions confirmed the occurrence of fat migration and recrystallization during bloom formation.