Heat-sealing bioplastics in food packaging: an eco-friendly approach

Isha Mahesh Desai, Parvatibai Chowgule College of Arts and Science

Petroleum-based plastics have an application in almost all areas, ranging from households to industry and pharmaceutical companies. However, the increasing pressure on the environment due to the deposition of non-biodegradable plastics in landfills and the rising costs of petroleum has created concerns about switching to an innovative environment-friendly alternative. Bioplastics (bio-based materials) is an idea proposed by researchers to valorize waste biomass and reduce pollution due to petroleum-based plastics.

This article discusses a study of interactions of reduced graphene oxide (rGO) on starch-chitosan blended film and its heat-sealing property. The film was composed of 75% thermoplastic starch and 25% antioxidant and antimicrobial chitosan, mechanically reinforced by rGO. Hydrophobic surface, low water solubility, improved antioxidant activity, electrical conductivity, and heat-sealing ability are some of the properties exhibited by this blended film that make it a suitable alternative for active food packaging.

Properties of the heat-sealing eco-friendly bioplastics:

Polysaccharides extracted from renewable bio-waste have an application in the synthesis of biopolymers. Starch is the most abundant storage polysaccharide of plants with low cost, non-toxicity, and good film-forming capacity. Sources for starch extraction include corn, cassava, maize, potato, and rice by-products. It comprises two macromolecules- amylose and amylopectin. High amylose content increases the film’s thermal, mechanical, and barrier properties.

The thermoplastic ability and heat-sealing property of starch make it a competitive polymer. Poor mechanical strength, fragility, and water solubility are some drawbacks of starch that are overcome by blending it with another polysaccharide- chitosan. Chitosan is a structural polysaccharide with non-toxic, biodegradable, biocompatible, film-forming properties. It is extracted from the exoskeleton of crustaceans and confers antimicrobial and antioxidant properties to the blended film. Incorporating reinforcing agent-rGO into the blend film induces electrical conductivity into the biopolymer to sterilize food products with pulsed electric field (PEF) technology.

How was the study performed?

For the preparation of heat-sealing bioplastics, different proportions of polysaccharides were mixed in a fixed ratio along with rGO and glycerol to prepare a blended solution. The films were prepared by solvent casting methodology and named according to the polysaccharide proportions as S75:C25, S50:C50, and S25:C75. Characteristics of the films were studied through various experiments:

1. Structural and morphological characteristics: The ATR-FTIR (Attenuated total reflectance- Fourier transform infrared spectra) analysis helped detect possible interactions between starch and chitosan chains and rGO fillers. Hydrogen bonds between rGO and polysaccharide chains indicated good miscibility between matrices and fillers.
   SEM (Scanning electron microscope) was used to analyze the film’s compatibility and the effect of rGO addition. The starch-chitosan blended film showed a smooth surface indicating good compatibility, the addition of rGO conferred a rough wave-like morphology indicating homogenous dispersion of fillers throughout the polymer.
2. Wettability and solubility of the film: The starch-chitosan film wettability analysis was performed by WCA (Water contact angle). The hydrophobic nature of chitosan is responsible for good surface hydrophobicity. The addition of rGO has no considerable difference in the film property. The water solubility of the film was tested by its weight loss in distilled water. Solubility is affected by high chitosan concentration. However, the presence of rGO enhances water resistance and maintains the structural integrity of the film.
3. Mechanical and antioxidant properties: A high chitosan mass fraction improves the blended film’s stretchability and elasticity. It also shows high antioxidant activity. Adding rGO increases stiffness and decreases stretchability, acting as a reinforcing agent.
4. Electrical conductivity and heat-sealing property: The rGO dispersion in the matrix determines the electrical conductivity of the film. However, high starch concentrations also enhance the conductivity of the bio-nanocomposite. A high starch mass fraction leads to the highest seal strength due to the thermoplastic ability of starch.

Thus, heat-sealing bioplastics made with the combination of 75% starch-25%chitosan-rGO in food packaging with active properties are best suited and help maintain the safety of packaged food for a longer time than plastics.

Also read: Scientific Content Writing Training & Internship Program

Reference:

Alves, Z., Ferreira, N. M., Ferreira, P., & Nunes, C. (2022). Design of heat-sealable starchchitosan bioplastics reinforced with reduced graphene oxide for active food packaging. Carbohydrate Polymers, 291, 119517.
https://doi.org/10.1016/j.carbpol.2022.119517

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