**7. Rheology of edible films**

Ideally, the functional characteristics of a packaging film, more especially the physical and rheological characteristics of a film-forming solution, can be used to verify the film's performance (FFS). In fact, rheological characteristics are crucial to the creation of high-quality composite films. They must be taken into account while enhancing the design process since they have an impact on the spreadability, thickness, uniformity, and functioning of FFS [164]. It is well-known fact that physical parameters of film plays are crucial to investigate the properties, such as tensile strength, Young's modulus, and elongation at break. In addition, the physical characteristics of films were also examined, such as their shape, morphology (heterogeneous and homogeneous), solubility as well as their transparency, and light transmission. The rheological characteristics associated with the film-forming solutions play a crucial role in defining properties, such as thickness, dispersion, and uniformity of liquid coating layer, applied to the edible film by dipping brushing or spraying. Also, with respect to film formation, a moderate viscosity is the required flow property for the film-forming solution since high or low viscosities would result in uneven film formation [165]. For coating applications, some writers have advised a viscosity lower than 700 mPas; however, the proper viscosity for other film solution treatment circumstances, such as mixing, pumping, and transfer to the casting line, as well as spreading the solution smoothly, is around 1000–10,000 mPas [166, 167]. The behavior of the flow of film solutions has an impact on the mechanical properties and the optimization of the designing process during application. Additionally, it is claimed that rheological parameters can be used to assess how polysaccharide solution systems' structure–function interaction [168]. Therefore, modification and alteration in the molecular structure, it is required to analyze the rheological characteristics of the edible film solutions in order to provide a comprehensive understanding of the physical characteristics of edible films.

Ideally speaking on influence of concentration degree of deacetylation (DD), for example, an increase in the concentration of glycerol has a significant influence on apparent viscosity (AV), consistency coefficient (CC), and flow behavior index values of deacetylation samples. In one study addition of 5% glycerol has shown descending order of AV and CC of prepared films. At a subsequent addition of glycerol (10%), these values did, however, continue to decline for only 100DD samples. The samples' pseudoplastic behavior was shown by the n values, which ranged from 0.70 to 0.77

#### *A Study on Edible Polymer Films for Food Packaging Industry: Current Scenario… DOI: http://dx.doi.org/10.5772/intechopen.107997*

[169]. Principally, it was connected to the network's polysaccharide macromolecules with a lot of hydroxyl groups being destroyed by shearing [170]. In terms of pseudoplastic flow behavior, AV, and CC values, only the 100DD-10G (n = 0.77) sample was less favorable. As a result, this solution disperses and flows more readily, reflecting the fact that glycerol has disrupted the intermolecular link among the glucomannan polysaccharides. Therefore, glycerol's inhibition impact was more pronounced for 100DD. Glycerol increase may be offered at a lower DD, preserving the properties of the existing hydrogen bonds while creating new ones.

In our previous work, we tried to figure out influence of *Syzygium cumini* (*S. cumini*) leaves extract, morphological, thermal, and mechanical as well as on antimicrobial activity of the PVA and PVA/chitosan blend films for packaging applications [171]. The findings showed that the *S. cumini* leaves extract in PVA and PVA/ chitosan films had a significant physical interaction at lower concentrations, which contributed to the films' smooth uniform morphology, increased degree of crystallinity, lower degradation temperature, and improved mechanical properties. **Table 3** depicts the mechanical properties of PVA and PVA/chitosan-doped blend films. As it is observed that at a lower concentration of *S. cumini* leaves extract, tensile strength increased, elongation at break and Young's modulus decreased. **Figure 4** depicts the SEM micrographs of pure PVA, chitosan, PSN-1, PSN-4, PCS-1, PCS-3, PCSHN-1, PCHSN-3, PCHS-1, and PCHS-4 blend films [171].

**Figure 5** it is depicted that, binary PVA/S. cumini leaves extract showed smooth homogeneous morphology, whereas high concentration of S. cumini leaves extract


#### **Table 3.** *Mechanical properties of PVA, chitosan, and blend films.*

**Figure 4.**

*SEM micrographs of pure PVA, chitosan, PSN-1, PSN-4, PCS-1, PCS-3, PCSHN-1, PCHSN-3, PCHS-1, and PCHS-4 blend films [171].*

(PSN-4) showed low compatibility exhibiting strand-like appearance, indicating phase separation. Similarly, in another work, we tried to analyze influence of Betel leaves extract on chitosan/vanillin films [91].

*A Study on Edible Polymer Films for Food Packaging Industry: Current Scenario… DOI: http://dx.doi.org/10.5772/intechopen.107997*

#### **Figure 5.**

*Scanning electron microscopy micrographs of pure chitosan, vanillin, betel leaf extract, CH/BE (CBE) and CH/ Vn/BE (CVB, CVBA) blend films [91].*

**Figure 6** presents the SEM micrographs of different Betel leaf extract (BE) doped chitosan blend films. At a lower concentration of BE, smooth homogeneous morphology was observed (CBE-1), later at a higher concentration of BE immiscibility was noticed (CBE-4). In case of ternary blend films Chitosan/vanillin/BE, showed good

**Figure 6.** *Edible films and coatings: schematic presentation [172].*

miscibility and smooth homogeneous morphology (CVB-1 and CVBA-1) due to compatibility of BE at molecular level as chitosan is recovered by the vanillin network implying the appreciable adhesion and compatibility [91]. Similarly, X-ray diffractogram of binary chitosan/BE films showed a significant change in 2θ value, indicating the decrease in degree of crystallinity (51.59, 70.89, and 31.94%) with an increase in the filler BE, attributed to the dispersion of BE lead to the weak interaction in the chitosan matrix. The diffraction model of ternary CH/Vn/BE blend films showed diffraction peaks at 18.50, 20.39, 28.50, 35.09 and 42.19° for CVB-1; 22.2, 31.09, 34.30 and 44.90° for CVB-2; and 7.06, 20.59, 22.79, 28.49 and 38.49° for CVB-3. The 2q value in each

*A Study on Edible Polymer Films for Food Packaging Industry: Current Scenario… DOI: http://dx.doi.org/10.5772/intechopen.107997*

formulation was significantly improved by the addition of BE, lengthening the distance between the chitosan chains. The findings from the contact angle investigation and the oxygen barrier qualities may be closely connected with this [91].

#### **8. Concerns relating to consumers**

Consumer acceptability may have a considerable impact on the potential usage of edible materials because edible films are consumable components of food products [1]. Consumer acceptability, which is influenced by organoleptic characteristics, welfare, selling, and cultural resistance to the use of new materials, is a comprehensive indicator of consumers' subjective product preferences. However, it is important to note down organoleptic characteristics, including flavor, odorless, sensory feasibility with packed foodstuffs, texture, and appearance [135]. Innovative edible film's potential for toxicity or allergenicity and microbiota changes in packaging stuffs are major safety concerns. More than consumer approval, there are several other issues that prevent edible films from being used commercially, including complexity associated with the production, huge investment to install new film manufacturing equipment, potential conflict with traditional packaging, and regulatory issues.

#### **9. Applications**

Heightened active packaging concept is a result of growing consumer demand for retaining quality and freshness of foodstuffs higher quality. A kind of packaging material that modifies the environment around the food to preserve food quality and freshness, enhance sensory qualities, or lengthen food safety and shelf life. In this regard. Edible films are considered suitable candidates for packaging as they are eco-friendly and biodegradable in nature. Generally, edible films are used to pack vegetables, fruits, meat, fish, dairy products (cheese, milk, and yogurt), and poultry products. Various examples of packaging materials include biopolymers, bioplastics, and edible films prepared from natural origin raw materials from agricultural or marine sources [78].

#### **9.1 Edible films for meat, poultry, and seafood packaging**

Generally, active edible films provide a preservative barrier to products made from meat, poultry, and seafoods. As this food is quite perishable due to high percentage of water. Edible films around the meat products protect the shrinkage loss, retain discoloration, resist microbial attack, and oxidative off-flavor. A variety of edible biopolymers are employed as coatings for meat products [173, 174]. With advantageous properties, such as biopolymer, hydrophilic, and good film-forming ability, author Kontominas MG have investigated sodium alginate-based edible films by mixing active and antimicrobial agents to enhance the shelf-life of meat product [175]. Author Takma and colleagues prepared the alginate-based edible films using black cumin oil as an antimicrobial agent to pack chicken breast meat [176]. Furthermore, Qussalah et al. have proved sodium alginate films successfully inhibit Salmonella typhimurium when mixed with cinnamon, savory, and oregano oil [177].

However, Seafood is most perishable food material which has a very short shelf life also contamination possibilities are more during transportation due to surrounding

environment, which leads to the spoilage of quality and loss of nutritional values and may lead to foodborne diseases. To ensure quality and shelf-life use of antimicrobial agents in the catfish gelatin which helps to control microbial attack and enhances the shelf life of shrimp by nearly about 10 days. Gelatin and whey protein-based enriched films doped with cinnamon oil and clove essential oil as an active antimicrobial agent retards the microbial attack on rainbow trout fish and active agent improves the quality of chicken breast fillet's shelf life [178, 179].
