INTRODUCTION:
Foods are rich in nutritional factors like carbohydrates, fat, proteins, minerals and vitamins. The nutritional factors are obtained from plants, animals and fungi. Before consumption, food undergoes processing, preservation and packaging. Materials science is a field that consists of physics, chemistry and engineering subjects, which deal with properties of materials, transformation, strength, surface and phase equilibria of the materials (Stanley, 1994). Food materials science is an emerging field and it is a combination of food engineering and science. Food materials science includes food processing, preservation and retention of the quality of foods. As far as Food Materials Science is concerned, plenty of operations are carried out, some of them being unit operations, food physics, food packaging, etc. These operations involve converting the raw material into edible foods for consumption (Tung & Britt, 1995). Bio-based polymers are considered environment-friendly, as they become decomposed very easily as compared to common plastics. In the development of packaging materials, natural polymers have a significant role, owing to their biodegradability and barrier ability against moisture, gas and aroma. The commonly used biopolymers for packaging are shown in Fig.1.
Bio-based polymers can be functionalized by the addition of substances such as colourants (pH indicators), antimicrobials, antioxidants, flavour absorbents, scavengers, gas and moisture absorbers, bio-based sensors, etc. to serve as smart packaging systems. Packaging plays an important role in the food sector. This article mainly focuses on biopolymers, being a sustainable packaging material and their applications in food packaging.
BIOMATERIALS IN FOOD PACKAGING
Currently, biopolymers are being commonly used in food packaging, owing to their ease of availability and disposal. Biopolymers are classified into four categories based on their origin i.e. polymer extracted from biomass, synthetic polymers from biomass monomers, polymers produced by microorganisms and biodegradable polymers synthesized from petrochemical monomers. In this article, we will discuss about cellulose, hemicellulose, chitosan and starch and their uses in food packaging (Wang et al., 2021).
Cellulose
Cellulose is the most abundant biopolymer available in the nature and it is cost-effective, non-toxic, biocompatible, biodegradable and chemically stable. It is also widely used for edible packaging. Cellulose is present in plants, green algae & cyanobacteria. The presence of cellulose in plant cells is shown in Fig. 2.
Cellulose is a linear polysaccharide consisting of many β (1-4) linked D- glucose units. This is commonly classified into two groups i.e. cellulose ethers and cellulose esters (Madhu et al., 2018). Cellulose is not soluble in water, but it undergoes solubilization in organic solvents. Usually, synthesized cellulose is used for food packaging, owing to its excellent dimension and mechanical stiffness. Also, it is used in edible packaging, owing to its highly transparent nature. Cellulose possesses antibacterial and antifungal properties and it helps to reduce the microbial spoilage that occurs in the food products. Cellulose also acts as an active packaging with nanoparticles and preservatives. Besides, it acts as intelligent packaging associated with plant-based extracts like carotenoids, anthocyanin and astaxanthin and it indicates the colour changes during food deterioration (Wang et al., 2021).
Hemicellulose
Hemicellulose is referred to as branched polymers that contain pentosans and hexosans. In addition, it comprises of many side chains and it has good water-soluble and film-forming properties. In hemicellulose, xylans are the most common, which is present in dicotyledons. It possesses good barrier properties against oxygen. As hemicellulose is combined with any other polymer, it can yield good thermal stability under processing and is an eco-friendly material.
Chitosan
Chitosan is referred to as a cationic biopolymer synthesized by de-acetylation of chitin. It consists of amino and hydroxyl groups; It shows high antimicrobial activity against gram-positive and gram-negative bacteria. The de-acetylation process of chitin was shown in Fig.3.
The alkyl chitosan, quaternary chitosan and carboxymethyl chitosan are some of the water-soluble chitosan used as an effective package with better barrier properties for food materials (Kumar et al., 2020).
Starch
Starch is a combination of linear amylose and branched amylopectin. It is a semicrystalline polymer with low solubility. Starch is rich in potatoes, tapioca, corn, etc. as shown in Fig. 4.
Due to low flexibility, it is not widely used for food packaging purposes. To address this issue, some plasticizers, enzymatic treatments and physicochemical modifications are done to improve the flexibility of starch. Therefore, acetylated starch is used for coatings and it shows good water vapour barrier properties for food packaging. Likewise, the composite film made from starch, incorporated with some essential oils and pectin had better thermal stability, barrier property and mechanical property for food packaging (Mendes et al., 2020).
ELECTROSPINNING IN FOOD PACKAGING
Active packaging is one of the emerging techniques in food packaging. It is focused on the shelf life enhancement of food products. The antimicrobial agents added in food polymers have some limitations, due to their instability, volatility and lack of interaction with food components (Yuan et al., 2017). To overcome these limitations, encapsulation techniques are employed. Therefore, using these encapsulation techniques in some of the studies, it had been observed that it has created a positive impact on microbial spoilage. Some of the studies related to this technique against microbes are listed in Table 1. Nowadays, electrospinning is widely used to encapsulate bioactive agents.
Electrospinning is a technique using a high voltage electric field applied to a polymer solution that comprises of bioactive compounds, which results in the formation of nanofibers. In food packaging, both natural and synthetic electro-spin nanofibers are widely used. The electrospinning technique for matrix design is represented in Fig.5.
As compared to synthetic polymers, natural polymers have low toxicity, biocompatibility and better sustainability. However, natural polymers also have some disadvantages, due to its poor thermal stability, mechanical and barrier property. The electrospinning technique can be applied to different food commodities for better packing. Hence, emulsion, blend and coaxial electrospinning are three different methods to produce nanofibers through electrospinning (Hemmati et al., 2021; Bhushani and Anandharamakrishnan, 2014).
Conclusion
In this article, we have summarized the role of biopolymers in food packaging. Currently, biopolymers (cellulose, hemicellulose, chitosan and starch) are playing an important role in food packaging, owing to their ease of use, including biodegradability. Biopolymers are incorporated with nanoparticles and biological extracts, with specific functions to enhance the shelf life of food products. Electrospinning techniques were used for the fabrication of the matrix, which is entrapped with some extracts having better antimicrobial activity towards microbial spoilage in foods. Therefore, these food biopolymers based materials may become suitable for the novel packaging development, including its application in the storage of perishable foods.
References:
1. Bhushani, J. A., & Anandharamakrishnan, C. (2014). Electrospinning and
electrospraying techniques: Potential food based applications. Trends in Food Science
& Technology, 38(1), 21-33.
2. Ciesielski, P. & Crowley M. (2020), Cellulose nanodefects: The key to biofuels and biomaterials of the future. https://researchoutreach.org/articles/cellulose-nanodefects-key-biofuels-biomaterials-future/
3. Cui, H., Wu, J., Li, C., & Lin, L. (2017). Improving anti-listeria activity of cheese
packaging via nanofiber containing nisin-loaded nanoparticles. LWT-Food Science and
Technology, 81, 233-242.
4. Hegenbart, S. (1996). Understanding starch functionality. Food Prod. Design January, 23-34.
5. Hemmati, F., Bahrami, A., Esfanjani, A. F., Hosseini, H., McClements, D. J., & Williams, L. (2021). Electrospun antimicrobial materials: Advanced packaging materials for food applications. Trends in Food Science & Technology, 111, 520-533.
6. Islam, M. M., Shahruzzaman, M., Biswas, S., Sakib, M. N., & Rashid, T. U. (2020). Chitosan based bioactive materials in tissue engineering applications-A review. Bioactive materials, 5(1), 164-183.
7. Kumar, S., Mukherjee, A., & Dutta, J. (2020). Chitosan based nanocomposite films and coatings: Emerging antimicrobial food packaging alternatives. Trends in Food Science & Technology, 97, 196-209.
8. Madhu, B., Patel, S., Rao, P. J., & Sreedevi, P. (2018). Use of edible coatings to increase the shelf life of jaggery: A review. International Journal of Current Microbiology and Applied Sciences, 7(6), 2466-2479.
9. Mendes, J. F., Norcino, L. B., Martins, H. H. A., Manrich, A., Otoni, C. G., Carvalho, E. E. N., … & Mattoso, L. H. C. (2020). Correlating emulsion characteristics with the properties of active starch films loaded with lemongrass essential oil. Food Hydrocolloids, 100, 105428.
10. Meral, R., Alav, A., Karakas, C., Dertli, E., Yilmaz, M. T., & Ceylan, Z. (2019). Effect of electrospun nisin and curcumin loaded nanomats on the microbial quality, hardness and sensory characteristics of rainbow trout fillet. LWT, 113, 108292.
11. Soto, K. M., Hernández-Iturriaga, M., Loarca-Piña, G., Luna-Bárcenas, G., & Mendoza, S. (2019). Antimicrobial effect of nisin electrospun amaranth: Pullulan nanofibers in apple juice and fresh cheese. International journal of food microbiology, 295, 25-32.
12. Stanley, D. W. (1994). Understanding the materials used in foods—Food materials science. Food research international, 27(2), 135-144.
13. Tung, M. A., & Britt, I. J. (1995). Food material science and food process engineering: Keys to product quality and safety. Food research international, 28(1), 101-108.
14. Wang, J., Euring, M., Ostendorf, K., & Zhang, K. (2021). Biobased materials for food packaging. Journal of Bioresources and Bioproducts.
15. Yuan, W., Lee, H. W., & Yuk, H. G. (2017). Antimicrobial efficacy of Cinnamomum javanicum plant extract against Listeria monocytogenes and its application potential with smoked salmon. International Journal of Food Microbiology, 260, 42-50.
