Validation of a benchtop USAXS system for analyzing cocoa butter microstructures

The preferred chocolate of consumers possesses physical qualities such as good snap, gloss, and brittle hardness. Traditional tempering relies on the formation of stable form V crystals to achieve these qualities but can exhibit varied mechanical properties. This suggests that factors beyond final crystal form, such as microstructure and nanostructure are important. The microstructure of cocoa butter (CB) can be effectively studied using ultra-small angle X-ray scattering (USAXS) via synchrotron radiation; however, the accessibility of synchrotron facilities is often limited. This research aims to validate and extend the capabilities of an in-house benchtop USAXS system for characterizing CB microstructures and understanding their impact on mechanical properties. Scattering data from tempered and untempered cocoa butter samples will be collected using a slit-type benchtop USAXS instrument and desmearing algorithms will be applied to account for slit smearing. The resulting power-law slopes can reveal the fractal nature of the crystalline microstructure in the low q region alongside Guinier curves that contain information about the size of the structures. In addition, an investigation of various processing conditions including tempering techniques, different cooling and shear rates of CB samples will be conducted to modify the microstructure. The resulting microstructural differences will be correlated with functional outcomes. Complementary microscopy techniques will provide additional insights into the bulk and surface microstructure. Powder X-ray diffraction (XRD) will confirm the polymorphic states of CB crystals. Overall, this research demonstrates the potential of benchtop USAXS instruments as a practical and reliable tool for studying the microstructure of CB. Understanding the microstructural and mechanical relationship within CB can improve the energy intensive processes required to temper chocolate products. Extending USAXS research to other edible fat systems may be useful to advance the characterization and optimization of various fat-based products.