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

Size distributions are characteristic of the processing steps the product underwent. Examples of high-fat emulsions and the corresponding rehydrated powders. (A) Unhomogenized emulsion in its native state (solid line), with addition of EDTA (●), and with SDS (×). Emulsions and rehydrated powders (B) with a 20-MPa homogenization and (C) without homogenization pressure. Symbols: after homogenizing (◊), after spray atomization (□), and after drying (▴). The phase-contrast micrographs were taken in the rehydrated powders (scale bar: 10μm).

Thermal profiles of the emulsions reflecting fat organization. Example of crystallization profiles of fat in the high-fat emulsions and in anhydrous coconut oil in bulk. a.u.=arbitrary units.

Confocal laser scanning micrographs of high-fat powders after a 6-mo storage period (A) with a 20-MPa homogenization, and (B) without homogenization pressure. Fat appears in the gray level. The solid arrow indicates free fat and the open arrow indicates coalesced fat. V stands for vacuole. Scale bar: 20μm.

Homogenization conditions (i.e., fat droplet size) and total fat content were the parameters having the most influence on the free fat content. ^a-dDifferent letters above the bar plots indicate significant differences at P<0.01.

Melting profiles of the powders reflecting the structure of fat crystals and the lactose state: melting profiles of fat and glass transition of lactose within the high-fat unhomogenized powder during storage. The solid arrow indicates the second melting peak of fat and the open arrow indicates the signal of the glass transition of lactose. T_g stands for the glass transition temperature of lactose. a.u.=arbitrary units.

Thermal profiles of the powders reflecting the fat supramolecular structure: crystallization and melting profiles of fat within the high-fat unhomogenized powder before (solid line) and after (dashed line) free fat extraction. a.u. = arbitrary units.