# Protein–Polysaccharide Bilayer Films: Influence of Protein and Cross-Linker on Interfacial and Functional Properties

## TL;DR

This paper explores how combining proteins and polysaccharides with different cross-linkers can create strong, functional biobased films.

## Contribution

The study introduces new insights into how cross-linkers and protein types influence the performance of bilayer biobased films.

## Key findings

- Gelatin layers showed strong adhesion across various pH levels, suggesting minimal electrostatic influence.
- Casein-CMC films required tannic acid for effective adhesion.
- BTCA improved water vapor barrier properties but reduced mechanical resistance in casein-CMC films.

## Abstract

Self-supporting bilayer films were produced by combining
a protein
(casein or gelatin) and a polysaccharide (carboxymethylcellulose,
CMC). Effective interfacial interactions, achieved either physically
(primarily via electrostatic interactions) or chemically (with citric
acid and 1,2,3,4-butanetetracarboxylic acid (BTCA) as cross-linkers),
granted improved mechanical and functional performance. Gelatin layers
exhibited strong adhesion across different pH values (3, 4.5, and
8), indicating a minimal role of electrostatic forces in interlayer
interactions. In contrast, casein required the incorporation of tannic
acid (TA) into the CMC layer as a compatibilizing agent to achieve
effective adhesion. Polysaccharide cross-linkers were evaluated in
casein-CMC bilayers, where citric acid reduced the water absorption,
while BTCA improved water vapor barrier properties but decreased mechanical
resistance. Understanding interfacial interactions enables the design
of biobased materials with tailored properties, boosting competitiveness
and functionality within the circular bioeconomy.