Heat-stable whey protein isolate made using isoelectric precipitation and clarification

Area of Science:

• Food Science and Technology
• Dairy Science
• Protein Chemistry

Background:

• Residual lipids (RL) in whey protein isolate (WPI) negatively impact functional properties like foaming and turbidity.
• RL also contribute to off-flavor development in WPI powder during storage.
• Current methods for RL removal, such as microfiltration, can be costly and complex.

Purpose of the Study:

• To develop an alternative method for preparing WPI with reduced RL without using microfiltration.
• To compare the functional properties of this experimental WPI with commercially available WPI.
• To investigate the impact of pH, conductivity, and protein concentration on RL precipitation.

Main Methods:

• Whey protein concentrate (WPC-34) was acidified to pH <5.0 to approach the isoelectric point of denatured proteins and phospholipoproteins.
• Demineralization was achieved using ultrafiltration (UF) and diafiltration (DF) with acidified water.
• Precipitated RL and associated proteins were removed via centrifugation or clarification.
• Experimental WPI was produced by concentrating, neutralizing, and spray-drying the treated whey protein solution.

Main Results:

• Optimal precipitation of RL occurred at pH 4.5-4.7 and lower conductivities achieved through UF/DF.
• Protein concentrations ≤3% maximized RL sedimentation due to increased density difference.
• Electrophoresis confirmed the removal of phospholipoproteins and denatured proteins with RL.
• Experimental WPI powders (91% protein, <1.8% fat db) showed comparable functional properties to commercial WPI after accelerated storage.

Conclusions:

• A novel, non-microfiltration method effectively removes RL from WPI by exploiting isoelectric precipitation and demineralization.
• The experimental WPI demonstrates excellent functionality, heat stability, and low turbidity.
• This approach offers a promising alternative for producing high-quality WPI with improved storage stability.