Effect of crosslinking on the properties of sodium caseinate films

Abstract

Protein films are used as effective lipid, oxygen, and aroma barriers at moderate relative humidity conditions. However, they perform poorly as moisture barriers. The introduction of crosslinks within or between protein chains by enzymatic or chemical modification has been proposed as an alternative means to achieving a stronger polymeric matrix structure, which would result in better functional film properties. In this article, we report the preparation and characterization of sodium caseinate (SC) films crosslinked by glutaraldehyde (GTA) or heat. The crosslinking density increased with GTA content. The thermal stability and tensile modulus and strength increased with GTA content, although films with a low crosslinking density exhibited lower properties than the uncrosslinked sample. Unexpectedly, water vapor permeability and absorption also increased with crosslinking density. The crosslinking of SC was also induced by simple heating. The resulting films showed enhanced thermal, mechanical, and barrier properties compared to the unmodified SC films and even the GTA-crosslinked samples. GTA crosslinking was unable to reduce the high hydrophilicity of the SC films. Thermally induced crosslinking was revealed to be a valid alternative for improving the properties of SC films, without the inherent complications associated with the use of a chemical crosslinking agent.

Improvement on Physical Properties of Pullulan Films by Novel Cross‐Linking Strategy

“…It infers that the strong intermolecular interaction took place after crosslinking reaction, leading to particle projections on the homogeneous surfaces. The excess amount of glutaraldehyde may result in cracks inside the films (Pereda and others ), which was not observed in our results. The addition of glycerol reduced the small projections along the films for both molecular weight pullulan films (Figure ), consisting with the above results indicating that glycerol enhanced the solubility of pullulan films.…”

Structure and properties of nanocomposite films based on sodium caseinate and nanocellulose fibers

“…Regarding the possible reasons for this behavior, one of the mechanisms proposed by Azizi Samir et al (2004) can be used to explain our findings: the solid surface of cellulose whiskers could restrict mobility of polymer chains in the vicinity of the interfacial area, which would result in a global shift of T g toward higher temperatures. In any case, it should be noticed that not only the moisture content of the films is decreasing as the test progress but also that cross-linkage in sodium caseinate films can be induced simply by heating (Pereda et al, 2010). In other words, the ''softening" temperature of the samples is changing as the test advances and cannot be ascribed to the standard T g .…”

Keratin/Polyvinyl Alcohol Blend Films Cross-Linked by Dialdehyde Starch and Their Potential Application for Drug Release

“…For example, in drug-release applications, a high film integrity and stability in a humid environment are required over a relatively long period of time. Generally, cross-linking is the most common and useful method to reduce the TSM of protein-based films in water [37][38][39]. The TSM values obtained for the FK/PVA blended films cross-linked by DAS in water at 37 °C are listed in Figure 4.…”