Properties of Whey-Protein-Coated Films and Laminates as Novel Recyclable Food Packaging Materials with Excellent Barrier Properties

Abstract

In case of food packaging applications, high oxygen and water vapour barriers are the prerequisite conditions for preserving the quality of the products throughout their whole lifecycle. Currently available polymers and/or biopolymer films are mostly used in combination with barrier materials derived from oil based plastics or aluminium to enhance their low barrier properties. In order to replace these non-renewable materials, current research efforts are focused on the development of sustainable coatings, while maintaining the functional properties of the resulting packaging materials. This article provides an introduction to food packaging requirements, highlights prior art on the use of whey-based coatings for their barriers properties, and describes the key properties of an innovative packaging multilayer material that includes a whey-based layer. The developed whey protein formulations had excellent barrier properties almost comparable to the ethylene vinyl alcohol copolymers (EVOH) barrier layer conventionally used in food packaging composites, with an oxygen barrier (OTR) of <2 [cm³(STP)/(m²d bar)] when normalized to a thickness of 100 μm. Further requirements of the barrier layer are good adhesion to the substrate and sufficient flexibility to withstand mechanical load while preventing delamination and/or brittle fracture. Whey-protein-based coatings have successfully met these functional and mechanical requirements.

Improvement of Food Packaging-Related Properties of Whey Protein Isolate-Based Nanocomposite Films and Coatings by Addition of Montmorillonite Nanoplatelets

“…For sorbitol-plasticized nanocomposite coatings, with exception of coatings with 9% (w/w protein) nanofillers, the OP also decreased but, however, the effect of the increasing nanofiller loading toward the OP was not as clear as for glycerol-plasticized coatings. The renewed increase in OP at 9% (w/w protein) nanofillers could be explained by the orientation of the nanoplatelets within the protein network as with further addition of nanofillers the OP started to decline again until it reached its least permeability of approximately 0.58 cm 3 m −2 day −1 bar −1 at the highest filler loading which is in the range of the permeability values of EVOH (Schmid et al, 2012). These results underline that WPI-based nanocomposite coatings are capable of replacing commercial petroleum-based barrier polymers, e.g., ethylene-vinyl alcohol copolymer (EVOH 44%) which is used in multilayer flexible packaging applications as an effective barrier against gases and particularly against oxygen permeation.…”

“…3, whereby di represents the thickness of the individual layers (di, d = ∑di), and Pi represents the permeation coefficient of the individual layers (Pi, P = ∑Pi). Alternatively, the total permeability of a multilayer structure can be calculated from the respective permeabilities of the individual layers, Qn, whereby the superscripts (1 and 2) represent the respective layers (Schmid et al, 2012):…”

“…Protein-based films in general are good barriers against the diffusion of small gas molecules like oxygen or carbon dioxide due to their hydrophilic nature (Miller and Krochta, 1997). However, the incorporation of plasticizers, e.g., polyols, increases the permeation coefficient (Lieberman and Gilbert, 1973;Schmid et al, 2012) due to increased absorption of moisture into the hydrophilic biopolymer network which consequently leads to increased intermolecular spacing as supported by free-volume theory (Lieberman and Gilbert, 1973). As glycerol, compared to sorbitol, shows a higher hygroscopicity (Shaw et al, 2002), its effectiveness in increasing the free-volume and thus increased permeation of oxygen molecules could be attributed to the structure of polyol plasticizers as glycerol is much smaller than sorbitol and thus, based on their molecular weight, more abundant at the same weight-% bases.…”

UV Radiation Induced Cross-Linking of Whey Protein Isolate-Based Films

“…A glycerol plasticized denatured whey protein standard solution (WPSS) containing 10% (w/w) WPI was prepared according to the procedure developed by Schmid et al [3]. Films were casted into Petri dishes with a target thickness of 50 m (final thicknesses were 39 ± 16.1 m) and dried at ambient conditions in a climate chamber at 23 ∘ C and 50% RH until equilibrium was proved by constant weight.…”

“…Those also include biodegradable packaging materials from renewable raw materials such as wheat gluten, soy protein, casein, or whey proteins [2]. Whey protein isolate-(WPI-) based films showed high barrier performance against oxygen, leading to suitable biomaterials for packaging applications [3]. WPI consists of different whey proteins, linked by thermal, chemical, biochemical, and/or physical treatments [4], such as ultraviolet (UV) irradiation.…”