Aldehyde compounds were importantly increased after the HPT treatments. In fact, they were the most abundant chemical group (in terms of AAU) found in processed human milk. This is an important concern since high levels of aldehydes in milk have been commonly associated with oxidized off-flavor or oxidative rancidity in this matrix. Based on the origin, we have identified different aldehydes in human milk: (1) aldehydes which are produced from lipid oxidation, and (2) aldehydes derived from the Maillard reaction. The latter are usually more complex aldehydes, such as 2-furaldehyde, 2,5-furancarboxaldehyde, and 5-(hydroxymethyl)-2-furancarboxaldehyde, while aldehydes originated from lipid oxidation are lineal aldehydes, such as hexanal, heptanal, 2-heptenal, octanal and 2-decenal (Namiki, 1988, Friedman, 1996 and Elisia and Kitts, 2011).