Material and Environmental Properties of Natural Polymers and Their Composites for Packaging Applications—A Review

The current trend of using plastic material in the manufacturing of packaging products raises serious environmental concerns due to waste disposal on land and in oceans and other environmental pollution. Natural polymers such as cellulose, starch, chitosan, and protein extracted from renewable resources are extensively explored as alternatives to plastics due to their biodegradability, biocompatibility, nontoxic properties, and abundant availability. The tensile and water vapor barrier properties and the environmental impacts of natural polymers played key roles in determining the eligibility of these materials for packaging applications. The brittle behavior and hydrophilic nature of natural polymers reduced the tensile and water vapor barrier properties. However, the addition of plasticizer, crosslinker, and reinforcement agents substantially improved the mechanical and water vapor resistance properties. The dispersion abilities and strong interfacial adhesion of nanocellulose with natural polymers improved the tensile strength and water vapor barrier properties of natural polymer-based packaging films. The maximum tensile stress of these composite films was about 38 to 200% more than that of films without reinforcement. The water vapor barrier properties of composite films also reduced up to 60% with nanocellulose reinforcement. The strong hydrogen bonding between natural polymer and nanocellulose reduced the polymer chain movement and decreased the percent elongation at break up to 100%. This review aims to present an overview of the mechanical and water vapor barrier properties of natural polymers and their composites along with the life cycle environmental impacts to elucidate their potential for packaging applications.

Transglutaminase Applications in Dairy Technology

Consumers' expectations from a dairy product have changed dramatically during the last two decades. People are now more eager to purchase more nutritious dairy foods with improved sensory characteristics. Dairy industry has made many efforts to meet such expectations and numerious production strategies and alternatives have been developed over the years including non-thermal processing, membrane applications, enzymatic modifications of milk components, and so on. Among these novel approaches, transglutaminase (TG)-mediated modifications of milk proteins have become fairly popular and such modifications in dairy proteins offer many advantages to the dairy industry. Since late 1980s, a great number of researches have been done on TG applications in milk and dairy products. Especially, milk proteins-based edible films and gels from milk treated with TG have found many application fields at industrial level. This chapter reviews the characteristics of microbial-origin TG as well as its mode of action and recent developments in TG applications in dairy technology.

Physical, Chemical and Biochemical Modifications of Protein-Based Films and Coatings: An Extensive Review

Protein-based films and coatings are an interesting alternative to traditional petroleum-based materials. However, their mechanical and barrier properties need to be enhanced in order to match those of the latter. Physical, chemical, and biochemical methods can be used for this purpose. The aim of this article is to provide an overview of the effects of various treatments on whey, soy, and wheat gluten protein-based films and coatings. These three protein sources have been chosen since they are among the most abundantly used and are well described in the literature. Similar behavior might be expected for other protein sources. Most of the modifications are still not fully understood at a fundamental level, but all the methods discussed change the properties of the proteins and resulting products. Mastering these modifications is an important step towards the industrial implementation of protein-based films.

Tuning the Functional Properties of Polysaccharide-Protein Bio-Based Edible Films by Chemical, Enzymatic, and Physical Cross-Linking

Among natural biopolymers, polysaccharides and proteins are very promising for biodegradable and edible wraps with different characteristics, so that their formulations can be tailor-made to suit the needs of a specific commodity. Films prepared from polysaccharides have good gas barrier properties but exhibit lower resistance to moisture compared to protein films (edible) or polylactide films (biodegradable). Protein-based films show better mechanical and oxygen barrier properties compared to polysaccharide films. For that reason, film performances may be enhanced by producing blend systems, where hydrocolloids (mixtures of proteins and/or polysaccharides) form a continuous and more cohesive network. However, the lower water barrier properties of hydrocolloid films and their lower mechanical strength in comparison with synthetic polymers limit their applications in food packaging. Therefore, the enhancement of biopolymer film properties has been studied to attain appropriate applications. This review provides an extensive synthesis of the improvement of the properties of edible polysaccharide-protein films by way of various chemical, enzymatic, and physical methods. These methods primarily aim at improving the mechanical resistance. They also permit to ameliorate the water and gas barrier properties and related functional properties.

Determination and Quantification of Molecular Interactions in Protein Films: A Review

Protein based films are nowadays also prepared with the aim of replacing expensive, crude oil-based polymers as environmentally friendly and renewable alternatives. The protein structure determines the ability of protein chains to form intra- and intermolecular bonds, whereas the degree of cross-linking depends on the amino acid composition and molecular weight of the protein, besides the conditions used in film preparation and processing. The functionality varies significantly depending on the type of protein and affects the resulting film quality and properties. This paper reviews the methods used in examination of molecular interactions in protein films and discusses how these intermolecular interactions can be quantified. The qualitative determination methods can be distinguished by structural analysis of solutions (electrophoretic analysis, size exclusion chromatography) and analysis of solid films (spectroscopy techniques, X-ray scattering methods). To quantify molecular interactions involved, two methods were found to be the most suitable: protein film swelling and solubility. The importance of non-covalent and covalent interactions in protein films can be investigated using different solvents. The research was focused on whey protein, whereas soy protein and wheat gluten were included as further examples of proteins.

Microbial transglutaminase and its application in the food industry. A review

The extremely high costs of manufacturing transglutaminase from animal origin (EC 2.3.2.13) have prompted scientists to search for new sources of this enzyme. Interdisciplinary efforts have been aimed at producing enzymes synthesised by microorganisms which may have a wider scope of use. Transglutaminase is an enzyme that catalyses the formation of isopeptide bonds between proteins. Its cross-linking property is widely used in various processes: to manufacture cheese and other dairy products, in meat processing, to produce edible films and to manufacture bakery products. Transglutaminase has considerable potential to improve the firmness, viscosity, elasticity and water-binding capacity of food products. In 1989, microbial transglutaminase was isolated from Streptoverticillium sp. Its characterisation indicated that this isoform could be extremely useful as a biotechnological tool in the food industry. Currently, enzymatic preparations are used in almost all industrial branches because of their wide variety and low costs associated with their biotechnical production processes. This paper presents an overview of the literature addressing the characteristics and applications of transglutaminase.