Composition gradient from surface to core in dairy powders: Agglomeration effect

Gradient compositions in standard and agglomerated industrial milk powders were studied. X-ray Photoelectron Spectroscopy (XPS) coupled with Energy Dispersive X-ray (EDX) analyses were used to investigate respectively the first 5 nm and the first micrometer of the particle surface. From these results, two models were proposed concerning the distribution of milk components (lactose, lipids, proteins and minerals) from the particle surface to the core. Concurrently, different milk fat fractions (total, encapsulated and free fat) were extracted from standard and agglomerated powders and analyzed by Differential Scanning Calorimetry (DSC) as well as Gas Chromatography (GC). Similar thermal characteristics but variable fatty acid profiles were found between these fractions. No difference between standard and agglomerated powders was observed in both gradient composition and fat fractions properties, suggesting that agglomeration process don’t change the particle surface properties.