**3.1 Chitosan and chitin-based coatings and films**

Insects, crustaceans, and fungi use the naturally occurring mucopolysaccharide chitin, which is composed of 2-acetamido-2-deoxy-β-D-glucose molecules connected by -bonds, as a structural component (1-4). Chitosan, a concentrated alkali-induced N-deacetylated derivative of chitin, is produced in this environment. Chitosan and chitin are alike to cellulose in their excessive insolubility degree and low chemical reactivity. Solubility of chitosan depends on N-acetylation degree and molecular weight, also it can be dissolved in acid solutions where pH is less than 6.3 even at a concentration above 2% (w/v). Rheological properties, solubility, and appearance, among other properties of chitosan properties, are also dependent on the Nacetylation degree.

Similar to cellulose, chitosan and chitin has a high insolubility degree and minimal chemical reactivity. Chitosan may dissolve in acid solutions with a pH lower than 6.3 at concentrations of more than 2% (w/v), and its solubility is proportional to its Nacetylation degree and molecular weight. Chitosan's N-acetylation level affects not only its rheological qualities but also its solubility and appearance. The potential of chitosan-based films and coatings to act as natural preservatives is widely known.

#### **Figure 2.**

*A diagram representing the various components discussed in the chapter i.e., polysaccharide matrix (chitosan and alginate), functional materials (phenolics, essential oils, and nano-forms), and matrix incorporated with functional materials for improving the overall properties of the edible coatings/films. Here m (α-L guluronic acid) and n (β-D mannuronic acid) (Source: [10]).*

Coatings and films made of chitosan are permeable to gases (O2 and CO2), have excellent mechanical properties, and also have high permeability to water vapor, which limits their use in humid environments, since controlling moisture transfer is a desirable property. For this main reason, several plans have been made to improve the functional properties of chitosan coatings and films. As can be seen, its functional coating qualities may be improved by adjusting factors such as the degree of solvent, pH, deacetylation, and the addition of surfactants, proteins, lipids, or polysaccharides. Essential oils boost water vapour permeability and give antibacterial and antioxidant benefits. A number of reagents, such as ferulic acid, genipin, glutaraldehyde, formaldehyde, cinnamaldehyde, and sodium trimetaphosphate, are added to the formulation to slow down the dissolving or swelling and enhance the characteristics of chitosanbased coatings. Their main use is in food processing as a functional food and helps in Encapsulation antimicrobial agent and also works as plant growth-promoting agent.

For the effective use of chitosan coating, the chitosan was to be combined with other substances. As seen, the single chitosan coating was oftentimes combined with physical methods that are short heating, short gas fumigation, and modified atmosphere packaging (**Figure 2**) [11].

#### **3.2 Alginate-based films and coatings**

Gels or insoluble polymers may be formed from sodium alginate, a well-known polysaccharide, due to its strong reactivity to polyvalent metal cations. Since it may create a semipermeable barrier on fruits and vegetables, it has been widely utilized as an edible covering for preserving foods like apples and peaches [10]. Marine brown algae are a rich natural source of the polysaccharide alginate (Phaeophyceae, majorly Laminaria). Pseudomonas and Azotobacter are two bacterial families that contribute to its development. Alginate is a linear copolymer of (1–4) β-D-mannuronic (M) and α-L-guluronic (G) acid, and it is the salt of alginic acid. These acid residues are located in M or G-residue blocks (also known as MG-blocks) or in MG-residue blocks. M: G residue distribution and percentage differ across algal species. Because nano coating has the potential to extend the shelf life of many food goods, it is seeing rapid growth.

Silver-containing materials are shown to exhibit bactericidal or anti-microbial properties, which led to their strong development in the last few years [12]. Alginates are infamous for their good film-forming properties and performance [13]. Alginates are globally used in edible coatings because of their good availability and regulatory status. The United States Food and Drug Administration (FDA) classifies food-grade sodium alginate as generally regarded as safe to use (**Figure 3**) [14].

#### **3.3 Nano liposome**

Its main application is in the Food processing industry and its main use is in specific delivery of nutraceuticals and active and passive delivery of genes, protein & peptides, and also the delivery of pesticides and fertilizers.

#### **3.4 Colloidosomes**

Colloidosomes also called Pickering emulsion capsules, have gained a lot of attention for the Encapsulation of hydrophilic and hydrophobic activities [15]*.* These are microcapsules whose shell comprises tightly packed colloidal particles. Their physical properties like permeability, mechanical strength, and biocompatibility can also be

*Using Nanotechnology for Enhancing the Shelf Life of Fruits DOI: http://dx.doi.org/10.5772/intechopen.108724*

#### **Figure 3.**

*The role and mechanism of action of functional materials in enhancing the shelf-life of fruits. (A) The matrix of alginate/chitosan along with functional additives acts as a water and O2 barrier for inhibiting respiration and eventually reactive oxygen species generation. The specialized coating also inhibits the spoilage of fruits by microbes and UV light. (B) Phenolics, essential oils, and nanoparticles destabilize microbial membranes, which can perforate cells and block protein synthesis, causing electrolyte leakage and ultimately cell death. Nano-metallic forms generate (ROS) like hydroxyl radicals, and SOD and result in organelle damage. They further restrict the synthesis of DNA, RNA, and lipids required for the survival of the microbes. (C) These functional materials mainly phenolics act as antioxidants and prevent fruits from being damaged by reactive oxygen species. (D) The synergistic effect of alginate/chitosan-based coatings with functional additives maintains the appearance, flavour, and extends the shelf-life of fruits and vegetables. Here ROS (reactive oxygen species), total soluble solids, titratable acidity, and total ascorbic acid content.*

controlled by the proper choice of colloids and preparation conditions for their assembly [16]. Colloidosomes are also used in the Food processing unit and their main application is increasing the nutrient content of food.

#### **3.5 Casein micelles**

Casein micelles show hydrophobic and hydrophilic properties that make them ideal for encapsulation of food bioactive [17]*.* Its main application is as a nutritional supply that helps in the delivery of sensitive products.

#### **3.6 Alginate and chitosan**

Alginate and chitosan are used to coat the nanoparticles and make negative and positive charges available on the particles [18]. Their main application is as a target delivery supply that supplies B-carotene, lycopene, vitamins A, D, E, and omega-3-fatty acids.

#### **Figure 4.**

*Overview of the mechanism of the synergistic effect of alginate/chitosan matrix and functional additives (phenolics, essential oils, nano-forms). (A) Acting as an O2 barrier. (B) Acting as an antioxidant. (C) Acting as anti-microbial. The overall action of (A), (B), and (C) results in a prolonged shelf-life of fruits and vegetables (source: (Table 1) [10]).*

#### **3.7 Nano cochleate**

Nano cochleates' main application is in Nutritional supply where Nutrients are efficiently delivered without affecting colour and taste (**Figure 4**) [6].
