Plants, algae and marine seafoods are important resources to obtain natural polymers that can be used for designing sustainable packaging. Historically, different natural materials, e.g., plant and animal parts, shells, ceramics, and others, were the firstly used materials by the ancient populations for food packaging [1]. The Industrial Revolution and the World War II were significant events that boosted the discovery, design of new packaging materials and novel processing strategies. Aluminum cans by canning operation and the coming up of petroleum-based plastics are some typical examples ^[2][3][2,3]. Afterwards, conventional plastics were extensively used for packaging. As their majority has a single use only, usually ends up polluting landsites and aquatic environments. It was estimated that, only in 2015, around five billion tons of plastic waste ended up in natural sites [4]. Because of this problem, reducing petroleum-based pollution should be top priority of all nations around the world. More than 170 United Nations Member States have committed to reduce the use of plastics until 2030 [4]. In this way, replacing conventional plastics for biobased materials is a sustainable approach that contributes to reducing plastic pollution. Consequently, the synthesis and use of biobased materials for packaging design has increased over the past few years.

Besides being environmentally friendly and emitting low greenhouse gases, natural materials can be obtained from different renewable sources, such as plants, animals, microorganisms and their residues, making them extensively available [5]. This is also an advantage when compared to conventional plastic polymers, since the latter are petroleum-based, a nonrenewable resource. Natural polymeric materials, such as plant- or marine-based polysaccharides and proteins, are naturally biodegradable, which means that they can be degraded by local microorganisms and return to nature [6]. Natural polymers have important technological and biological properties, which allow their utilization for food packaging. Generally, these materials display good film-forming and gelling properties, which leads to consider them distinguishable and sustainable choices to prepare edible films and coatings. When applied to this end, biopolymeric films may exhibit some processing challenges. They present brittleness, low water and gases barrier properties, inferior mechanical behavior, characteristic of their nature [7]. The incorporation of hydrophobic substances or blending two or more biopolymers to form composites consist of alternative approaches to overcome these technological issues [8].

2. Some Natural and Renewable Macromolecules Used to Prepare Edible Films and Coatings

A wide range of natural polymers from renewable sources has been used in the development of biobased food packaging. The main natural sources for this purpose are derived from polysaccharides, proteins, lipids, or blends of these macromolecules ^[9][10][36,37] (Figure 13). The utilization of these natural materials is partly linked to its biodegradability and renewability. However, some other advantages are expected when used for food packaging, e.g., as these materials can act as carriers of functional substances adding well-being benefits, incorporating flavorings and colorings aspects, enhancing organoleptic characteristics, improving mechanical and barrier resistance, and others [8]. Polysaccharides are known to possess good oxygen barrier and to have sites for hydrogen bonding formation, which can be used for incorporation of functional substances, e.g., coloring, flavoring, and antioxidants agents. By contrast, these materials do not exhibit good barrier to water vapor, which can be overcome by blending with other hydrophobics macromolecules, such as lipids ^[7][8][7,8]. Polysaccharides have been used to develop natural-based packaging ^[7][9][7,36]. Plant-derived proteins have gained remarkable attention of food manufactures and consumers in search for natural food resources and alternative materials to vegetarian, vegan, and food allergy diet restrictions. Protein-based film packaging exhibit extraordinary mechanical and barrier properties, especially to oxygen and carbon dioxide gases, when compared to polysaccharides ^[7][11][7,38]. Besides being eco-friendly materials, these films can nutritionally improve food quality and preservation. Moreover, the amphiphilic attribute of proteins contributes to their utilization as emulsifiers by stabilizing oil/water interface due to changes in interfacial tension ^[12][39]. Nowadays, a great variety of plant proteins have been used in food industry and packaging, such as from soybean, wheat, corn, sunflower, and pea ^[13][40]. Edible films can be defined as a thin layer of a material coating or placed between foods, in which act as a barrier ad that can be consumed without any health risk ^[8][11][8,38]. Both are a primary food packaging and can be thought similar, although they differ substantially. Mainly, films are solid laminates, separately prepared, dried, processed and then used to cover food surface, placed between food parts, or used as an edible sealed bag ^[7][14][7,41]. Differently, coatings are prepared as a solution, directly sprayed or dipped on the food surface and then dried ^[15][42]. Thus, coatings can be considered as a part of the food product, since they are not made to be removed [8]. Moreover, films can be prepared as a mono, bi or multilayers. The latter provide a better water barrier to food but are less commonly used as they need two or more processing steps of casting and drying [7]. Both films and coatings should be composed only by food-grade components, GRAS (Generally Recognized as Safe), including any additives, such as plasticizers ^[15][42]. As any other packaging, these materials must protect the food integrity and maintain its quality ^[8][14][15][8,41,42]. In Figure 24 is presented the main purposes of edible food packaging. Although, it is not expected that the edible films could replace completely all conventional packaging, they can be used to significantly reduce the use of petroleum-based plastics, decrease food losses, and reduce the environment pollution over a long-term. Edible films and coatings may have in their composition two main based materials, a biomacromolecule matrix and additives, such as plasticizers, cross-linkers, other reinforcements substances and functional ingredients ^[16][14]. These materials can be used alone or blended. Edible packaging composed by natural-based materials can be classified as a subgroup of biobased and biodegradable packaging [8]. Generally, polysaccharides, proteins, lipids, and their mixtures are used for the development of edible films and coatings. The classification and some examples of these natural materials commonly used for this purpose are presented in Table 1.