Enhancing milk powder quality through electrostatic spray drying: a comprehensive study on off-flavor formation and lipid oxidation

The shelf-life of dry dairy ingredients is generally limited by flavor defects arising from lipid oxidation. Therefore, it is critical to find strategies to mitigate lipid oxidation and subsequent off flavor formation in dairy powders. This research aims at investigating the application of electrostatic spray drying (ESD) to produce full fat milk powders with reduced heat exposure and a less oxygen-permeable particle structure to enhance the quality and shelf-life of dairy powders. Milk powders were produced by the traditional spray drying (TSD) and ESD at four different voltages (-18 kV, -2 kV, 2 kV, and 18 kV). The effects of EDS on fatty acid profile, primary lipid oxidation products (free and bound oxylipins) and secondary products (volatile profile) were accessed by gas chromatography coupled to flame ionization detection (GC-FID), liquid chromatography couple to mass spectrometry in tandem (LC/MS/MS) and gas chromatography couple to mass spectrometry (GC-MS), respectively. The main polyunsaturated fatty acid found in the powders was the linoleic acid (C18:2, n-6 LA, 3.44% in TSD, followed by 3.46% in ESD). ESD was effective in producing milk powders with significantly reduced concentration of free LA-derived oxylipins, including hydroxides such as 9- and 13-hydroxyoctadecadienoic acid, ketones, such as 9- and 13-oxo-octadecadienoic acid, and epoxides such as 9(10)- and 12(13)-epoxyoctadecamonoenoic acid in comparison with TSD powders. However, no significant difference was observed for bound oxylipins. ESD was also able to produce powder with significantly lower concentration of volatile compounds such as aldehydes, including hexanal, heptanal, and nonanal. Our results demonstrate that ESD is a promising technology for producing higher-quality milk powders. However, further shelf-life studies are necessary to fully understand the effects of this technology on product stability, nutritional quality and flavor properties over time.