Skimmed milk structural dynamics during high hydrostatic pressure processing from in situ SAXS

Area of Science:

• Food Science
• Materials Science
• Biophysics

Background:

• Understanding milk's nanostructure is key for improving dairy product safety and functionality.
• High-pressure (HP) treatment is a promising method for modifying food structures.

Purpose of the Study:

• To investigate the in situ nanostructural modifications of skimmed milk during high-pressure treatment.
• To analyze the effects of pressure, temperature, and time on milk protein structures.

Main Methods:

• Small-angle X-ray scattering (SAXS) was used to study skimmed milk under various HP conditions (200-400 MPa, 25-60°C, 5-10 min).
• Single- and double-HP treatments were applied, and dynamic structural changes were monitored.
• SAXS data were analyzed using a three-population model to characterize micelle size and protein inhomogeneities.

Main Results:

• HP treatment significantly affected casein micelle size and internal protein structures.
• Colloidal calcium phosphate (CCP) scattering was observed at 60°C, a feature typically seen with neutron scattering.
• Structural changes were found to be pressure-dependent and could be reversible or irreversible based on processing conditions.

Conclusions:

• HP treatment induces significant, pressure-dependent changes in skimmed milk nanostructure.
• Temperature also plays a crucial role, influencing CCP scattering and overall structural modifications.
• The study provides insights into controlling milk's structural properties through HP processing for enhanced functionality.