Insights into the physicochemical properties of coffee oil

The lipid fraction of roasted coffee is an interesting ingredient that could be used in a large number of food formulations. Coffee oil has peculiar flavouring as well as nutraceutical characteristics. The feasibility of the use of coffee oil as ingredient greatly depends not only on its chemical characteristics but also on its physical properties. The crystallisation and melting properties of the coffee oil extracted from Arabica roasted coffee powder were determined by using synchrotron X-ray diffraction coupled with differential scanning calorimetry. The fatty acid composition and the flavour profile were also assessed by using GC and GC-MS analyses, respectively. The main fatty acids found in coffee oil are linoleic and palmitic acid. Significant amounts of stearic and oleic acid are also present. These chemical characteristics are linked to the phase transition behaviour. The crystallisation of coffee oil occurs at 6.5 +/- 0.3 degrees C, independently of the cooling rate applied (from 0.5 to 10 degrees C/min). A unique crystalline structure was identified: a double chain length (2L) beta' structure (55.29 angstrom). The sole formation of the beta' form indicates that this metastable crystal is the only one that one should expect in foods containing coffee oil stored below 7 degrees C.