Fat properties during homogenization, spray-drying, and storage affect the physical properties of dairy powders

Abstract

Changes in fat properties were studied before, during, and after the drying process (including during storage) to determine the consequences on powder physical properties. Several methods were combined to characterize changes in fat structure and thermal properties as well as the physical properties of powders. Emulsion droplet size and droplet aggregation depended on the homogenizing pressures and were also affected by spray atomization. Aggregation was usually greater after spray atomization, resulting in greater viscosities. These processes did not have the same consequences on the stability of fat in the powders. The quantification of free fat is a pertinent indicator of fat instability in the powders. Confocal laser scanning microscopy permitted the characterization of the structure of fat in situ in the powders. Powders from unhomogenized emulsions showed greater free fat content. Surface fat was always overrepresented, regardless of the composition and process parameters. Differential scanning calorimetry melting experiments showed that fat was partially crystallized in situ in the powders stored at 20 degrees C, and that it was unstable on a molecular scale. Thermal profiles were also related to the supramolecular structure of fat in the powder particle matrix. Powder physical properties depended on both composition and process conditions. The free fat content seemed to have a greater influence than surface fat on powder physical properties, except for wettability. This study clearly showed that an understanding of fat behavior is essential for controlling and improving the physical properties of fat-filled dairy powders and their overall quality.

Fat supramolecular structure in fat-filled dairy powders: A tool to adjust spray-drying temperatures

“…2D). Fat droplet sizes below 1 μm are known to favor emulsion stability and enhance fat retention, as determined in previous studies [32,39]. It means that 90% of the total volume of fat droplets were fat droplets smaller than the critical size.…”

“…Methods are summarized hereinafter when identical to those previously detailed elsewhere [37,39]. Sampling was realized after (i) homogenization, (ii) spray atomization (i.e.…”

“…Figure 4 is a schematic representation of the above-discussed mechanisms. It was completed by the powder physical properties usually attributed to these fat supramolecular structures, in the literature and in our previous works [39].…”

“…The investigation of the surface composition was recently achieved by Fäldt et al [11], who adapted X-ray photoelectron spectroscopy (XPS) to the study of dairy powders. Since then, the technique has been largely used and the surface composition was related to powder physical properties such as wettability, flowability and stickiness [13,18,25,30,31,39]. Few studies considered the influence of fat droplet size and the measurement method was either laser light scattering [15,18,29,39] or, more arguably, image analysis of phase-contrast light micrographs [12,21].…”

Effect of Homogenization Pressure on Surface Fat Content in Spray-Dried Emulsions Stabilized With Milk Proteins

“…Emulsje o małych kuleczkach są efektywniej mikrokapsułkowane niż o dużych. W praktyce doświadczalnej przed suszeniem rozpyłowym emulsje poddaje się homogenizacji, aby otrzymać jak najmniejsze (~1 μm) i jednorodne kuleczki tłuszczu [16].…”