Control of thermal fabrication and size of β-lactoglobulin-based microgels and their potential applications

Factors influencing fabrication and size of microgels formed from β-lactoglobulin with or without pectin can tune selected attributes for material applications. Protein aggregation was expected to be influenced by pH, added anions, and reducing agents, while ionic strength was expected to be more influenced by electrostatically interacting pectin.

Turbidity measurements during thermal aggregation to form microgels were determined for pure β-lactoglobulin as a function of pH, added ionic strength, anion type (chloride, sulfate, and thiocyanate), and reducing agent concentration. β-lactoglobulin and pectin complexation pH values and thermal aggregation were determined by turbidity measurements with added potassium chloride, sulfate, and thiocyanate. Microgel size and morphology were determined by light scattering and atomic force microscopy, respectively.

Thermal aggregation of pure β-lactoglobulin increased with decreased pH, reducing conditions, and increased ionic strength with no observed anion effect. β-lactoglobulin microgel radii increased from 86 to 115nm with decreasing pH and increased to 124nm in reducing conditions, while salts promoted agglomeration. Increased ionic strength (0-100mmol/kg) decreased β-lactoglobulin-pectin complexation pH from 5.40 to 5.00, while first increasing and then decreasing thermal aggregation. Thermal aggregation and microgel size were greatest with potassium thiocyanate, followed by potassium chloride and potassium sulfate.