# Edible Packaging: A Technological Update for the Sustainable Future of the Food Industry
## 3 Results
### Alginate Films
#### 3.5.2 Protein-Based Packaging Materials  
Proteins are complex polymers whose amino acids are linked by covalent peptide bonds, which have a broad range of mechanical and physical characteristics, making them good for coating diverse food products. Proteins exist as fibrous (water-insoluble) or globular proteins (water-soluble proteins). Collagen, gelatin, casein, whey protein, soy protein, bean protein, wheat gluten, and peanut protein are examples of common proteins from animal and plant sources used for edible packaging [14]. Protein coatings have relatively high mechanical properties and provide effective barriers to gases like CO\({}_{2}\), O\({}_{2}\)[68], lipids, and aromas [36], but they have low water barrier properties [14]. Table 1 groups edible packaging materials based on different proteins. Milk proteins consist of ca. 80% casein and 20% whey protein and have the properties of malleable, transparent, and tasteless films [36]. These proteins also serve as carriers of additives like antimicrobials, antioxidants, and colorants, thereby enhancing the organoleptic properties of the packed products. The type of biopolymer and also the type and concentration of plasticizers employed in the preparation of the film has a significant impact on the thickness, barrier properties, and tensile strength of casein and whey protein films [60]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & **Material** & **Food Product** & **Method** & **Properties** & **References** \\ \hline \multirow{8}{*}{ \begin{tabular}{c} Proteins \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} Whey protein \\ isolates-nano- \\ emulsions of \\ _Grammoscidium_ \\ _ptocarpum_ \\ essential oil blend \\ \end{tabular}  } & \multirow{2}{*}{\ \begin{tabular}{c} Meat products, \\ nuts, fruit and \\ vegetables \\ \end{tabular}  } & \multirow{2}{*}{Casting} & \multirow{2}{*}{ \begin{tabular}{c} Improved mechanical \\ properties and lower \\ water vapor \\ permeability promote \\ of films. \\ \end{tabular}  } & \multirow{2}{*}{[59]} \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\  
Casein-based films are the most transparent of the protein-based films and also exhibit good elasticity and firmness, moderate surface hydrophobicity, thermal persistence, and low oxygen permeability. The main drawback of casein-based films, like most other protein-based films, is their low resistance to water vapor [69], and it is better to combine them with lipids to form composite films [70]. [PERSON] et al. [71] suggested the possibility of using tannic acid as a crosslinking agent to improve the physiochemical properties of casein-based films. Caseinate is the most common form of casein, which is highly water-soluble [33], but gets insoluble when subject to a buffer solution at pH 4.6 [72]. Calcium caseinate (CaCAs) and Sodium caseinate (NaCAs) are the most commercially available caseinates. Caseinates are made via casein precipitation by decreasing the pH to 4.6, either by adding a microbial culture or diluting mineral acid. After that, the casein curd is washed in water and then dissolved in an alkali appropriate to bring the pH up to approximately 7.0 before being spray-dried. If NaOH is selected to change the pH, sodium caseinate will be made, whereas if Ca(OH)\({}_{2}\) is selected, calcium caseinate will be produced [73]. Whey protein is a by-product or waste product of the dairy industry, which is another reason why it is selected as a component for producing edible films. The availability of whey protein and its potential applications in the production of gels, emulsions, and foams have attracted interest in the packaging industry. Because of this interest, whey protein is used to create films or coatings that protect food surfaces from chemical or microbial decay. As a result, this helps products maintain their high-quality standards and extend their shelf life [74]. whey proteins consist of whey protein isolates (WPI) and whey protein concentrates (WPC) and have differences in protein concentration.