Physical characterization of chocolates prepared with various soybean and milk powders

The physical characterization of chocolate products is vital in manufacturing, and the chocolate's processing time and composition directly influence physical properties, such as rheology and melting. The objective of this study was to investigate the effects of processing time and the ingredient types on the physical properties of milk chocolates containing soy milk powder and soy protein isolate. Characteristics of skimmed milk chocolate (SMC) and whole milk chocolate (WMC) were compared to soy milk chocolate and soy protein chocolate (SPC). Rheological data of chocolate products were fitted to Casson, Herschel-Bulkley, and Bingham models. The highest viscosity was observed for SPC samples, whereas yield stress was the highest for SMC samples after 2 hr of processing. The increase in milk and soy fats in the formulation softened the texture and decreased the whiteness index significantly (p < .05). PSD results show that SPC had the highest D90 (40.1 μm) and the lowest specific surface area (893 m² /kg) after 6 hr of processing. SPC samples had the narrowest particle size distribution observed by the span values. X-ray diffraction analysis showed that all the samples had the desired Form V, crystal form. The differential scanning calorimetry thermogram was used to determine phase transitions and melting behaviors. At the end of processing, melting enthalpies (ΔH_melt ) were significantly lower (p < .05) in milk chocolates.