In a scientific review paper published on February 19, 2016 in the peer-reviewed journal Packaging Technology and Science, Joaquín Gómez-Estaca and colleagues from the Instituto de Agroquímica y Tecnología de Alimentos, Valencia, Spain, provide a comprehensive overview of protein-based food packaging materials.
Food packaging materials made from renewable sources are seen as an environmentally friendly alternative to plastics. Biopolymers can be made out of polysaccharides, proteins, or lipids (for more information, please see FPF background article and dossier on bioplastics). The authors emphasize that among these three groups, protein biopolymers are the most versatile because of the many different building blocks (20 amino acids) and an even greater variety of functional groups that can be further modified. This combination allows creating biopolymers specifically tailored to the needs of a particular application.
The authors review the main protein sources that have been used in production of food packaging materials: corn zein, wheat gluten, soy protein, sunflower protein, milk proteins, muscle proteins, collagen and gelatin, and feather keratin. Further, manufacturing methods used for the production of protein-based biopolymers are described, with extensive application examples. These methods include wet processing and dry processing, the latter comprising thermo-pressing/thermoforming and extrusion. The authors also discuss different strategies that can help improving physico-chemical and mechanical properties of protein-based biopolymers, thus extending their areas of application. These strategies can rely on heat treatment, development of multilayer structures, blending different polymer types, adding particulate fillers, or cross-linking. These processes often require the use of additives, such as plasticizers, antioxidants, cross-linking agents, antimicrobials and micro-/nanoparticles. The question on the extent of migration of additives from protein-based polymers into food has not been addressed in this review.
The authors identify several critical issues that require special attention in order to ensure successful further development of protein-based biopolymers and their broader application in food packaging, namely (a) compatibility of protein polymer production with conventional industrial processes, (b) scaling up the production by extrusion technique, (c) further improvement of the mechanical, barrier, optical, and other relevant properties of protein-based biopolymers, (d) establishment of new protein sources that do not compete with human or animal feed, and (e) design of active packaging applications, where proteins can play an outstanding role because their hydrophilic nature allows for targeted release of deliberately added functional components. It has to be noted that safety assessment of protein-based food packaging materials (in particular regarding their ability to promote allergies or cause other adverse health effects) has not been discussed by the authors as one of the research priorities.
Reference
Gomez-Estaca, J. et al. (2016). “The potential of proteins for producing food packaging materials: A review.” Packaging Technology and Science (published February 19, 2016).
