POTENTIAL AND PITFALLS OF CELLULOSE NANOCRYSTALS IN ADVANCED PACKAGING MATERIALS: THEIR ROLE IN FOOD SAFETY

In this thesis, the studies of the 3-year doctoral thesis carried out at the PhD School in Food Systems of the University of Milan between 2018-2021 are presented. The thesis consists of 6 main chapters and each chapter is presented in the form of an article. The main purpose of the project was to investigate the safety of cellulose nanocrystals (CNCs) in detail when used as a food contact material, and to contribute to their safety assessments to take advantage of their use to increase the functionalities of packaging films without using petroleum-based plastic materials. First, a review (Chapter 1) was written to get better insight into what the engineered nanomaterials (ENMs) are and what the detection methods are to test them better. After a broad literature review, CNCs were taken as a specific case of ENMs and all the techniques for their characterization and the pros and cons of this material were discussed. A roadmap about the CNCs characterization was created based on recent guidelines published by EFSA. Then, CNCs were evaluated in-depth to define their physicochemical characteristics and morphological feature in Chapter 2 to be used as reference material for further studies. Additionally, the suspicion of the existence of CNCs in some products that are prone to human consumption sheds light on our work on this subject. Even if CNCs are not intentionally added to the food products we consume, they may have the potential to enter our bodies through the consumption of certain food products. For this reason, different kinds of microcrystalline cellulose (MCC) sources were chosen to represent a sort of approved cellulosic additive source. Due to their similar production ways which generally consist of a chemical acidic hydrolysis, possibly followed by ultrasonication, it was reasonable to search for the presence of CNCs in different MCCs. If the existence of CNC can be proven in MCC, safety concerns must change the direction. For this purpose, different sources of MCCs have been investigated to trace the possible presence of CNCs in Chapters 3 and 4 to support EFSA requirements for the safety of nanoparticles in the food chain. After the comprehensive characterization and detection of CNCs in different food additive sources, they were integrated into polymeric matrices in two different ways: as coating on polyethylene terephthalate (PET) films and as a reinforcement material in polylactic acid (PLA). Investigations to observe the migration and/or release of nano-sized matter from these polymeric combinations were done. Since the risk assessment of CNCs, in this case, requires new methodologies for their physicochemical characterization, a combination of advanced techniques that differ from traditional analytical techniques was used to study the migration. Therefore, in Chapters 5 and 6, the characteristics of the reference CNCs defined in previous chapters were used to investigate and define the nano-sized matter released/migrated from the polymeric matrices to the food simulants after the incubation period.