New Insights into the β Polymorphism of 1,3-Palmitoyl-stearoyl-2-oleoyl Glycerol

In this communication, we report on the discovery of two new triclinic crystal polymorphic forms (beta(3) and beta(2) ) of 1,3-palmitoylstearoyl-2-oleoyl glycerol (POS), the most abundant triacylglycerol molecular species in cocoa butter. Three distinct triclinic crystal forms were crystallized from acetone and were found to have melting points of 32.9 degrees C (beta(3)), 33.8 degrees C (beta(2)), and 38.7 degrees C (beta(1)), and enthalpies of fusion of 141.5 kJ/mol (beta(3)), 147.9 kJ/mol (beta(2)), and 158.5 kJ/mol (beta(1)). All crystal forms had a similar long spacing (d(001) = 64.1, 63.5, and 63.9 angstrom for /33, beta(2), and beta(1), respectively) but displayed distinctly different wide-angle scattering patterns, i.e., short-spacings. In this communication, we clarify the 60-yearold confusion related to the polymorphism of POS, a key component responsible for the mechanical and thermal properties, and ultimately quality, of chocolate.