More Tea, Less Plastic: Active, Degradable Food Packaging

: (Alternative Format Thesis)

Abstract

Food packaging forms part of a major global industry with substantial growth predictions towards 2030,and beyond. Food packaging enables the safety, quality, freshness, and accessibility of food productsfrom the supply chain to consumption. This industry contributes a vast proportion of municipal solidwaste. Biodegradable active packaging addresses two important environmental issues, plastic waste,and food waste. These next-generation packaging materials function to extend the shelf-life of food viathe release of antimicrobial and antioxidant compounds or the sequestration of degradation-enhancinggases. Chapter 1 aims to introduce and expand on the concepts of biodegradable active packaging,particularly focussing on the biopolymer source and the mechanisms of controlled release of the activeagent.In Chapter 2, a variety of different encapsulation methods were trialled with the aim ofachieving the controlled release of green tea extract from biopolymer films. The primary focus was todevelop a material based on green chemistry principles, utilising a bio-based, biodegradable polymer.Through a research and development process, cross-linking chitosan with vanillin to form a Schiff baseinteraction was evaluated as an effective mechanism for the controlled release of green tea polyphenols. In Chapter 3, the physiochemical properties of novel, cross-linked crustacean-derived chitosanfilms containing green tea polyphenols (CVGP) were evaluated. The thermal, tensile, surface,antibacterial and degradation properties of these films were investigated. The novel film performed wellas a potential active food packaging material and degraded to >90% mass loss within 12 weeks whenburied in soil. For the first time in the literature, the controlled release of an active compound fromwithin a vanillin cross-linked chitosan film was reported.In Chapter 4, the formulation of the cross-linked chitosan films was optimised, and novel thinfilms containing gallic acid as the active component (CVGGA), were evaluated for their physiochemicalproperties. This chapter focuses on the degradation of the polymer films in different environments,elucidating a potential mechanism for the enzymatic degradation of the material in soil. Furthermore,excellent antioxidant and antimicrobial properties were determined for this material and mechanicaland thermal properties were evaluated to be superior when compared to CVGP films. Lastly, completedegradation in soil within 24 weeks was determined.In Chapter 5, the synthetic protocol for CVGGA was applied to chitosan derived fromAgaricus Bisporus (white button mushroom). A suite of analysis was carried out on novel films madeivutilising an alternative feedstock for chitosan, evaluating an improved degradability of 100% mass losscompared to the crustacean-sourced films.In Chapter 6, the scope of the vanillin cross linked chitosan polymer matrix was extended viaapplication to intelligent packaging materials. Two distinct colorimetric sensor strips were developedusing curcumin and red cabbage extract in combination with crustacean-derived chitosan. Bothindicator films were applied to the degradation of prawns, providing a colorimetric output in accordancewith the increase in pH within the packaging headspace. This preliminarily work extended the scope ofcross-linked chitosan materials.

Date of Award	10 Dec 2025
Original language	English
Awarding Institution	University of Bath
Supervisor	Ming Xie (Supervisor) & Andy Burrows (Supervisor)