Methods’ combination to investigate the suprastructure, composition and properties of fat in fat-filled dairy powders

Adapting and combining specific biochemical and physical methods to investigate the properties of fat is the first step of an integrated approach conducted on fat-filled dairy powders, which have an economic and qualitative importance. The study includes the isolation, quantification and characterization of the free fat fraction, and the investigation of fat properties in situ in the powder. Free fat isolation is achieved by solvent extraction; the extracted fat can be quantified and further studied from thermal profile features by differential scanning calorimetry (DSC). Fat droplet sizes are investigated by laser light scattering: measurements are achieved on emulsions obtained after the rehydration of the powders. In situ methods mainly include investigation of the thermal properties by DSC, composition of the surface by X-ray photoelectron spectroscopy and qualitative observations by confocal laser scanning microscopy. After this study, reliable and connected methods are available (i) to quantify and locate the different types of fat within a powder particle and (ii) to investigate fat composition, structure and thermal properties. The need to combine several methods to conclude on a data set was demonstrated.