INTEGRATED GREEN STRATEGIES FOR THE MANAGEMENT, RECOVERY AND RECYCLING OF EXPIRED MILK.

The management of food waste and the adoption of biopolymers to replace plastics are crucial challenges for transitioning to a circular economy. This thesis addresses the knowledge gap regarding the reuse of expired pasteurized milk for producing biopolymeric films suitable for food packaging, combining technological innovation and environmental sustainability. Specifically, the research activities focused on the following objectives: optimizing experimental conditions for producing and functionalizing sodium caseinate (NaCas) from expired milk through chemical and physical treatments; developing a NaCas-based packaging prototype and assessing its performance in keeping low-moisture cheese snacks; conducting a life cycle assessment (LCA) of the production process from NaCas powder to the packaging prototype. In Chapter 1, the study explored the production of NaCas powders from expired milk, managing lipid content, and selecting plasticizers and casting methods to optimize film properties. Various experimental conditions were tested to ensure the quality and functionality of the NaCas films, resulting in a defined experimental protocol that can be used for film production. Chapter 2 focused on preparing film-forming solutions and producing films, investigating the role and characteristics of different amounts of fat in the powder, as well as different sonication techniques for degassing the film-forming solution and dispersing fat. The different films have been characterized for their mechanical, thermal, optical and barrier properties. The detailed analysis included testing different formulations and processing conditions, which demonstrated that converting expired milk can yield films with properties comparable to some synthetic materials Chapter 3 provided for the application of treatments such as LED exposure with photosensitizers and alkaline conditions to promote protein cross-linking, to enhance films properties. These treatments were designed to enhance the structural properties of the films, leading to improved performance in practical applications. Chapter 4 described the development of a NaCas packaging prototype for low-moisture cheese snacks. This activity involved collaborative efforts with Lactalis Italia to optimize the weldability of the NaCas film and the mechanical strength of the welds to obtain a flow-pack. Effectiveness in preserving product quality was evaluated by comparing the experimental prototype with the commercial packaging. Chapter 5 presented an LCA to evaluate the environmental impacts of the production process, from NaCas powder manufacturing to the final packaging prototype. This comprehensive assessment identified several opportunities to improve sustainability through process modifications, suggesting solutions to reduce environmental impact through scale-up of some production steps and the incorporation of eco-friendly additives. The results demonstrate the potential of expired milk as a valuable resource for developing sustainable biopolymeric films. By exploiting expired pasteurized milk, this research provides an effective solution for reducing food waste and raw material consumption, contributing to a more circular economy and alignment with SDGs. Future improvements include investigation of additives to reduce water vapor susceptibility of the film as well as mechanical properties, optimizing techniques for industrial scale-up, and implementing strategies to further reduce the environmental impact of the films. Additionally, exploring alternative production methods and new applications for the NaCas films can lead to broader adoption in the food packaging industry.