# Modification of Whey Protein Isolate with Surfactants Based on Hofmeister Series and Interaction Parameter

## TL;DR

This study explores how adding different surfactants to whey protein isolate changes its structure and properties, offering a way to tailor its behavior for thermoplastic applications.

## Contribution

The study introduces a surfactant-dependent strategy to modify whey protein isolate using Hofmeister series and interaction parameters.

## Key findings

- Surfactants altered the protein's secondary structure, converting α-helices into β-sheets.
- Rheological tests showed elastic modulus dominance over viscous modulus after thermal denaturation.
- Thermal stability decreased with surfactant addition, as observed in TGA.

## Abstract

Developing thermoplastic materials from proteins requires
structural
reorganization and stabilization of specific intermolecular interactions.
In this study, we modified whey protein isolate (WPI) with different
surfactantstwo cationic (cetylpyridinium chloride, CPC, and
benzalkonium chloride, BC) and one anionic (sodium dodecyl sulfate,
SDS)to evaluate their effects on the system’s structure
and thermal and rheological properties. The Hofmeister series and
interaction parameters between the components were taken into consideration.
Characterization was achieved by Fourier transform infrared spectroscopy
(FTIR), circular dichroism (CD), dynamic light scattering (DLS), thermogravimetric
analysis (TGA), differential scanning calorimetry (DSC), and parallel
plate rheometry. Results indicated changes induced by surfactants
in the secondary conformation of proteins, particularly, the conversion
of α-helical structures into β-sheets. Theoretical solubility
analysis (Flory–Huggins model) predicted the miscibility for
all surfactants. TGA found a greater reduction in the thermal stability.
Rheological analyses showed a predominance of the elastic modulus
(G′) over the viscous modulus (G″) even after thermal denaturation. Results were interpreted
based on the expected interactions between the surfactants and the
protein’s amino acids. Our findings suggest that modifying
WPI with surfactants can be an effective strategy to tailor its structural
and mechanical properties in a surfactant-dependent manner, provided
that a suitable balance between protein denaturation, molecular reorganization,
and thermal stability is maintained.