Critical phosphate salt concentrations leading to altered micellar casein structures and functional intermediates

Area of Science:

• Food Science
• Colloid and Interface Science
• Dairy Chemistry

Background:

• Micellar casein (MC) is crucial for dairy product texture.
• Understanding how additives like phosphate salts influence MC structure is vital for food processing.
• Phosphate salts are commonly used in dairy to modify protein interactions and functionality.

Purpose of the Study:

• To investigate the impact of various phosphate salts on the structural integrity of micellar casein (MC) at pH 7.0.
• To determine the critical salt concentrations affecting MC structure and properties.
• To elucidate the relationship between phosphate salt concentration and MC behavior.

Main Methods:

• Turbidity measurements of MC solutions at varying phosphate salt concentrations.
• Viscosity measurements of MC solutions under different salt conditions.
• Modeling turbidity reduction using an exponential decay function to identify the first critical salt concentration (C*).
• Identifying the second critical salt concentration (C**) corresponding to maximum apparent viscosity.

Main Results:

• Turbidity of MC solutions decreased exponentially with increasing phosphate salt concentration.
• A first critical salt concentration (C*) was identified, indicating the onset of MC disintegration, which decreased with longer polyphosphate chains.
• Apparent viscosity increased with salt concentration, peaking at a second critical salt concentration (C**), suggesting optimal protein interactions.
• Both C* and C** were found to be dependent on MC concentration.

Conclusions:

• Phosphate salt concentration significantly influences micellar casein structural integrity and solution properties.
• The identified critical salt concentrations (C* and C**) provide insights into the mechanisms of MC stabilization and destabilization.
• This study enhances the understanding of phosphate salt functionality in structuring dairy products.