Mechanical and spectroscopic characterization of crosslinked zein films cast from solutions of acetic acid leading to a new mechanism for the crosslinking of oleic acid plasticized zein films

Hazal Turasan; Emma A Barber; Morgan Malm; Jozef L Kokini

doi:10.1016/j.foodres.2018.03.063

Mechanical and spectroscopic characterization of crosslinked zein films cast from solutions of acetic acid leading to a new mechanism for the crosslinking of oleic acid plasticized zein films

Food Res Int. 2018 Jun:108:357-367. doi: 10.1016/j.foodres.2018.03.063. Epub 2018 Mar 22.

Authors

Hazal Turasan¹, Emma A Barber², Morgan Malm³, Jozef L Kokini⁴

Affiliations

¹ Department of Food Science Purdue University, 47907 West Lafayette, IN, United States. Electronic address: hturasan@purdue.edu.
² Department of Food Science Purdue University, 47907 West Lafayette, IN, United States. Electronic address: barber2@purdue.edu.
³ Department of Food Science Purdue University, 47907 West Lafayette, IN, United States. Electronic address: mmeiser@purdue.edu.
⁴ Department of Food Science Purdue University, 47907 West Lafayette, IN, United States. Electronic address: jkokini@purdue.edu.

PMID: 29735068
DOI: 10.1016/j.foodres.2018.03.063

Abstract

This study discovered through FTIR, FT-Raman and rheological measurements that glutaraldehyde binds to zein through the amine groups of glutamine turns by replacing the already-bonded oleic acid molecules and forming imine structures. As a secondary crosslinking mechanism, glutaraldehyde unfolds some of the α-helices and turns them into β-sheets. While crosslinking resulted in stiffer and less ductile zein films, it made the surface of the films rougher, measured using AFM, and more hydrophilic, measured using WCA. In the crosslinking conditions in this study, the number of crosslinks estimated from rubber elasticity theory were not enough to change the water vapor permeability of the films significantly. Improving the understanding of crosslinking mechanism and its effects on physical and chemical properties of zein films can be useful to develop stiffer, stronger and more durable platforms for biodegradable biosensors, microfluidic devices or scaffolds.

Keywords: AFM; Acetic acid; Crosslinking; FT-Raman; FTIR; Glutaraldehyde; Rheology; Zein.

MeSH terms

Acetic Acid / chemistry*
Cross-Linking Reagents / chemistry*
Elasticity
Food Packaging / methods*
Glutaral
Microscopy, Atomic Force
Molecular Structure
Oleic Acids / chemistry*
Permeability
Plasticizers / chemistry*
Rheology
Spectroscopy, Fourier Transform Infrared
Spectrum Analysis, Raman
Structure-Activity Relationship
Tensile Strength
Water / chemistry
Zein / chemistry*

Substances

Cross-Linking Reagents
Oleic Acids
Plasticizers
Water
Zein
Acetic Acid
Glutaral