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Development and characterisation of compostable, pectin-based films derived from the valorisation of fruit pulp sources for potential food packaging applications
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Date
2025
Authors
Hoque, Monjurul
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Publisher
University College Cork
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Abstract
The intensifying environmental crisis posed by synthetic plastic waste has catalyzed global efforts toward the development of biodegradable and sustainable alternatives for food packaging. This doctoral research addresses this challenge by exploring the valorisation of agro-industrial fruit waste particularly apple pomace as a renewable source of high-quality pectin, and its subsequent application in the formulation of high-performance, compostable films for active food packaging. The thesis adopts a holistic "source-to-function" strategy, combining green extraction technologies with bio-based composite material design and industrial-scale processing methods to deliver scalable and sustainable packaging solutions.
Initially, commercial pectin was used as a base material to develop functional films through solvent casting. Sodium alginate (sodium alginate) and calcium chloride (CaCl₂) were integrated with pectin to form ionic crosslinked matrices, reinforced with microcrystalline cellulose (MCC) for mechanical enhancement and geraniol (geraniol) for antimicrobial activity. This pectin/sodium alginate/MCC/geraniol system achieved notable reductions in water solubility and gas permeability, alongside full inhibition of foodborne pathogens such as Escherichia coli and Bacillus cereus, demonstrating excellent potential for active packaging applications.
To further improve film performance, banana sheath cellulose (BSC), an underutilized agro-waste-derived filler, was extracted and incorporated into pectin/κ-carrageenan (carrageenan) films. BSC effectively enhanced tensile strength, oxygen barrier properties, and thermal resistance. The introduction of linalool as a natural antimicrobial agent demonstrated synergistic functionality, with films exhibiting excellent antibacterial activity while maintaining structural integrity. Zinc oxide nanoparticles (ZnONPs) were later incorporated into pectin/carrageenan films alongside geraniol to create multifunctional nanocomposites. These films demonstrated improved processability, structural densification, enhanced mechanical properties, and potent antimicrobial action against E. coli and Listeria innocua.
A critical component of this research was the efficient extraction of pectin from apple pomace. High hydrostatic pressure (HHP) and ultrasound-assisted extraction (UAE) methods, individually and in combination with conventional extraction (CE), were systematically studied to optimize yield, molecular weight, and structural integrity. HHP at 200 MPa followed by CE yielded pectin with high molecular weight and excellent rheological properties, while
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hybrid UAE+CE extraction produced the highest yield and a structurally balanced pectin suitable for film formation. These findings underscored the role of moderate-pressure and synergistic extraction techniques in preserving pectin's functional properties.
Transitioning toward scalable production, plasticised pectin was blended with polycaprolactone (PCL) and processed through cast extrusion. Films containing pectin plasticised with 30% glycerol (pectin@30%Gly) demonstrated enhanced compatibility with PCL, improved oxygen barrier performance, and moderate mechanical strength, making them suitable for commercial processing. In a more advanced stage, ternary blends of PCL with thermoplastic pectin/carrageenan were developed via melt extrusion. Various ratios and functional additives (ZnONPs, MCC, BSC) were evaluated, with maleic anhydride (MA) used as a compatibiliser. BSC proved to be the most effective filler, enhancing tensile strength and thermal stability, while MA significantly improved matrix cohesion.
Finally, pilot-scale ultrasound-assisted conventional extraction (US-CE) of pectin from apple pomace was implemented, yielding pectin of suitable quality for film production. The extracted pectin was blended with PCL and processed into films via extrusion, validating the industrial scalability of the approach. Although some limitations in mechanical and barrier properties were noted due to partial phase separation, the films retained key functional characteristics and demonstrated the feasibility of large-scale application.
Overall, this thesis establishes a comprehensive framework for transforming food processing waste into value-added, functional packaging materials. By integrating sustainable raw material sourcing, green processing technologies, functional material design, and scalable manufacturing, this work contributes to advancing the circular bioeconomy. The developed pectin-based films, reinforced with natural fillers and active agents, represent a viable pathway toward next-generation, biodegradable, and compostable food packaging solutions.
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Controlled Access
Keywords
Pectin–carrageenan films , Apple pomace valorisation , Active food packaging , Zinc oxide nanoparticles , Green extraction technologies (ultrasound, high pressure)
Citation
Hoque, M. 2025. Development and characterisation of compostable, pectin-based films derived from the valorisation of fruit pulp sources for potential food packaging applications. PhD Thesis, University College Cork.