Synergistic action of chaotropic agents on the partial casein unfolding and solution stabilization for improved...

This study presents a synergistic strategy to enhance caseinate electrospinning and incorporation of plant-derived antioxidants, employing chaotropic agents to modulate protein conformation. Sodium dodecyl sulfate (SDS) and ethanol were used to disrupt the protein hydrophobic interactions and to promote unfolding of caseinate in highly concentrated (20 wt%) solutions. A minimal amount of polyvinyl alcohol (24 wt% relative to caseinate) was included to improve electrospinning while preserving the protein-dominant character of the matrix. Methanol and water extracts from rosemary and oregano were added at 1 and 3 wt% and their effect on solution behaviour and fibre functionality was evaluated. A notable reduction in cohesive energy density was observed from rheology studies, suggesting weakened protein - protein interactions, particularly at higher concentrations of plant extracts. This influences the electrospinnability and the fibres morphology. The conformational changes in the protein matrix, especially due to the perturbance of the ratio between the helical and turns structures, were evidence by FTIR spectroscopy from the subtle changes in the amide I band components. These are more pronounced for the rosemary water extract compared to the methanolic ones. The plant extracts provided enhanced hydrophobicity and functional performance; the fibres loaded with methanolic extracts exhibited significantly improved antioxidant activity, with DPPH radical scavenging increasing from below 2 % to approximately 56-68 % per mg. These results highlight the potential of using chaotrope-assisted caseinate/PVA electrospun fibres as sustainable, tunable carriers for bioactive compounds, offering promising applications, for example in active food packaging.