Recent progress in the development of coatings for paper food packaging applications

Abstract

Relevance and aim of the research: Many types of coatings have been developed to meet the demanding needs and properties of paper-based packaging, which is the most widely used sustainable category of food packaging. The purpose of this paper is to list and classify special sustainable coatings, such as bio-based coatings and coatings based on nanomaterials (NPs) that provide barrier, optical, mechanical, anti-microbial and other properties as well as additional functions to the final product for food paper packaging. Methodology and results: The study is an overview of the previously published works on trends and challenges in the development of healthy and eco-friendly for sustainable food paper packaging applications, which are green alternatives to conventional coatings. As known, paper/paperboard packaging, because of its structure made from cellulose fibers, is naturally sensitive to microbial attack due to the poor barrier properties (i.e., hydrophilicity, porosity, low grease resistance, high absorptivity to gases and water vapors). Thus, paper packages must be properly coated to withstand and keep the food safe, preventing temperature, humidity and other factors of the surrounding from affecting the composition of packaged food. However, the current market is based on the application of commonly used coatings, which are typically made from fossil oil or synthetic polymers, waxes and /or fluor-derivatives that improve surface hydrophobicity and barrier properties. Nowadays, the use of these materials is limited because of problems arising from fossil-oil resources, poor recyclability, and environmental issues. Therefore, these coatings must be replaced by new materials, with high biodegradability, recyclability and compostability features. Recent studies are focused on biopolymers including polysaccharides such as chitosan, starch, etc., proteins such as whey, wheat gluten, and zein, polyesters as polylactic acid (PLA), polycaprolactone (PCL), and polyhydroxyalkanoates (PHAs) that are investigated to formulate coatings with barrier properties for food packaging paper. Petroleum-based polymers are commonly used in paper coating. Due to the good affinity with the substrate, they create suitable barriers to gases and aroma and increase the mechanical strength of the paper packaging. Moreover, biopolymer products have been developed as counterparts to smoothly replace petroleum-based polymers., they can be made from natural raw materials and sources, such as vegetal and marine biomass, this way they can be biodegradable, nontoxic. Additionally, they act as a basis for the incorporation of additives with specific functions for coated paper (ie, active-antimicrobial properties). The methods of chemical modification and combination as well as the processing and production of these new coatings for paper packaging are still under investigation. The addition of certain nanoparticles (NPs) such as metals and oxides in biopolymers and green coatings could be advantageous to add value and enhance the processing, performance and functionality of food paper packaging. Conclusions & practical implications: The application of coatings on paperbased food packaging is extensively investigated to replace petrochemical derivatives by choosing environmentally friendly alternatives that come from natural and renewable resources. These options determine the ultimate recyclability, biodegradability and even compostability of the final product. The incorporation of certain nanomaterials in the coatings promises to provide a wide range of enhanced properties and improve barrier characteristics of the paper-based food packaging.