Although these compounds are naturally present in raw milk, most ketones can be formed during heat treatment by β-oxidation of saturated fatty acids followed by decarboxylation (Nawar, 2000) or by decarboxylation of β-ketoacids present in milk fat (Calvo & de la Hoz, 1992). Our results showed that not only temperature, but also pressure played an important role in the formation and/or degradation of ketones, since the combination with different temperatures produced diverse effects. At this respect, numerous authors have also reported that high pressure enhances oxidation of free fatty acids leading to the formation of ketone volatile compounds such as 2-heptanone (Oey et al., 2008 and Van der Plancken et al., 2012).