Analysis of volatile compounds in powdered milk for infant nutrition by direct desorption (CIS4-TDU) and GC-MS

Direct thermal desorption coupled with the Gas Chromatography-Mass Spectrometry (TDU-CIS4-GC-MS) technique applied to powdered milk was used as a novel approach for the characterization and quantification, as relative abundance, of volatile organic compounds (VOCs). The aim of this study was to exploit the potential applications and setup conditions of the CIS4-TDU-GC-MS technique for the identification of oxidized or non-oxidized samples of powdered milk for infant nutrition, subjected to accelerated aging through the changes in their VOCs profile over time. Thermal desorption at 30°C and subsequent cryotrapping at –40°C with a Gerstel Liner–in–Liner system, allowed a direct thermal desorption and cryotrapping of VOCs without any memory effect, thus avoiding sample preparation and contamination. The analyses led to the identification of several characteristic off-flavors in the oxidized samples, which were used as molecular markers to discriminate samples with different oxidation degrees. Finally, VOC contaminants possibly present in the packaging can also be identified with this technique.