Enhancing β-lactoglobulin recovery from sweet whey using chitosans of varying deacetylation degrees and chitosan-coated pea protein sponge

Sweet whey (SW), a byproduct of cheese production, is rich in β-lactoglobulin (β-LG) and other proteins. This study investigated two chitosan-based methods for β-LG recovery from SW: 1) direct precipitation using soluble chitosan and 2) adsorption on chitosan-coated natural sponge materials. Chitosan with degrees of deacetylation (DDA) of 75%, 85%, and 95%, as well as quaternary ammonium chitosan (QCTS), were tested in the direct precipitation method. Chitosan with a high DDA (95%) and QCTS exhibited superior performance, achieving the highest protein recovery of 82%. High-performance liquid chromatography (HPLC), SDS-PAGE and Fourier Transform Infrared Spectroscopy (FTIR) confirmed β-LG was the predominant protein recovered, which may be associated with electrostatic attraction between chitosan and β-LG. For the adsorption approach, increasing the chitosan surface coating concentration and moderately increasing glutaraldehyde (GTA) crosslinking improved the β-LG adsorption and the optimized sponge (20.0 mg/mL chitosan, 15.0 mL/L GTA) achieved high β-LG recovery of 93.8%. Compared with direct precipitation, the chitosan-coated sponge eliminates the need for centrifugation, offering advantages for continuous processing. Overall, this research presents a laboratory-scale chitosan-based approach for β-LG recovery from SW and provides a basis for future evaluation of solid-phase biopolymer adsorbents for whey protein recovery.