Synthesis and Identification of 3-Oxazolines in Cocoa

Adding water to chocolate is known to cause a large increase in the concentration of Strecker aldehydes, which are key aroma compounds in cocoa. 3-Oxazolines may be precursors responsible for this; however, only a low concentration of 2-isobutyl-5-methyl-3-oxazoline was previously identified in chocolate. This study investigates the possibility that other types of 3-oxazolines are the relevant precursors present in cocoa. A range of novel 3-oxazolines were synthesized and characterized by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy. Using the synthesized compounds as references, four of these were identified by GC-MS for the first time in aroma extracts of cacao nibs, cocoa liquor, and chocolate, obtained by solvent-assisted flavor evaporation. This study may reveal a new focus for enhancing cocoa aroma and potentially other roasted food products as well.