Non-destructive characterization of cocoa butter polymorphism in chocolate using Raman spectroscopy

Abstract: Cocoa butter is an edible fat derived from chocolate beans consisting primarily of palmitic acid and stearic acid, and cis-monounsaturated oleic acid. Cocoa butter exhibits polymorphism, or different crystal forms, and there are six known polymorphs of cocoa butter. Cocoa butter polymorphism is affected by additives, cooling conditions, temperature, and relative humidity. This aspect of cocoa butter is particularly important in the texture, shelf life, and appearance of chocolate confectionary products. The characterization of cocoa butter polymorphism can be measured using crystallographic, electrophoretic, thermal analysis, and spectroscopic analysis. Recently, dispersive Raman at excitation wavelengths close to the short infrared wavelengths (1000 nm-1064 nm) have enabled direct measurements of blooms and cocoa butter quality attributes in dark and milk chocolate. In this study, we provide an overview of the information provided by a Raman spectrum, including the presence of cis or trans isomers, fatty acid saturation, and polymorphic stability. The impact of cocoa butter substitutes, sweetener types, and tempering conditions on cocoa butter polymorph form was examined using dispersive Raman spectroscopy at 1000 nm. Our initial feasibility studies showed initial markers of cocoa butter quality to support non-destructive chocolate quality testing.