Tuning the Gel Network Structure and Rheology of Acid-Induced Casein Gels via Thiol Blocking

Area of Science:

• Food Science
• Materials Science
• Biochemistry

Background:

• Casein gels are crucial in food products.
• Thiol-disulfide interactions significantly impact protein gel properties.
• Understanding these interactions allows for tailored gel functionality.

Purpose of the Study:

• To investigate the role of thiol-disulfide interactions in casein gel structure and mechanics.
• To determine how blocking thiol groups affects gel properties.
• To explore the combined effects of heat treatment and thiol modification.

Main Methods:

• Preparation of acid casein gels from micellar casein (MC) powder.
• Heat treatment of MC suspensions at 70 °C.
• Variable blocking of thiol groups using N-ethylmaleimide (NEM).
• Characterization via stress-strain measurements, rheological analyses (G', G″), and confocal microscopy.

Main Results:

• NEM addition reduced gel strength by 50% but increased storage (G') and loss (G″) moduli by ~100%.
• NEM-treated gels showed uniform building blocks with whey protein coatings, enhancing short-term viscoelasticity.
• Control gels exhibited weaker viscoelasticity but higher compressive strength due to disulfide cross-links and broader particle size distribution.

Conclusions:

• Thiol blocking and heat treatment allow targeted modification of casein gel properties.
• High shear stability and low compressive strength can be achieved through specific thiol modification.
• Disulfide cross-links contribute significantly to the compressive strength of heat-treated casein gels.