PhD Defense:

Innovative approaches to food preservation and safety: development of active packaging and advanced microbiological screening

Food conservation and safety are major concerns in the agri-food sector. Food lost and waste, due to deterioration and microbial contamination, have a significant economic impact. Additionally, foodborne pathogens pose serious health risks to consumers. Conventional methods for food preservation and microbial analysis have limitations that urgently require innovation. This thesis aims to develop practical and sustainable solutions to enhance food quality and safety. Metallic and metal oxide nanoparticles (NPs) are versatile materials known for their unique properties such as antioxidant, antimicrobial, optical, and catalytic activities. They can be incorporated into packaging films to inhibit microbial growth and extend food shelf life. In this study, NPs were developed by doping TiO₂ with iron to obtain Fe₂TiO₅ NPs, which were found non- cytotoxic as demonstrated on Caco-2 cells. Furthermore, films incorporating Fe₂TiO₅ into alginate showednomigrationofironortitaniumionsintofood simulants, suggesting their safety as packaging materials. Fe₂TiO₅ also exhibited strong antioxidant efficacy, confirmed by a fresh fruit preservation test using alginate films containing Fe₂TiO₅. Alginate, a biodegradable material, offers an alternative to petroleum-based plastics, promoting sustainable food preservation. Two different solutions were studied to develop new methodologies for detecting foodborne pathogens. The first involved a colorimetric test to detect B. cytotoxicus spores, which pose a serious risk due to their resistance to industrial treatments. The detection principle is based on the peroxidase-like catalytic activity of gold nanoparticles (AuNPs) enhanced by the spores. The detection platform consists of a tube containing AuNPs and magnetic particles, both conjugated with an aptamer selected for its specificity towards B. cytotoxicus spores. Upon addition of the sample, the presence of spores is indicated by an increased color change of the solution, due to the oxidation of tetramethylbenzidine (TMB) in the presence of H₂O₂. The developed test enabled rapid and specific naked-eye detection of target spores directly in food items such as milk or mashed potatoes. The second test involved an electrochemical genosensor to detect Campylobacter, the most common cause of foodborne zoonoses. Detection was based on hybridization between a Campylobacter DNA sequence and a complementary DNA probe immobilized on a screen-printed gold electrode. After DNA probe immobilization, passivation with mercaptohexanol was carried out to reduce DNA molecule adsorptionphenomenaontheelectrodeandavoid nonspecific signals The study demonstrated promising detection capabilities. However, challenges regarding surface passivation and detection signal stability underscored the need for further optimizations. Overall, the thesis aims to improve food quality and safety, contribute to a more sustainable food system, and stimulate technological research and development.

Jury members

• Thomas Karbowiak, Professeur
• Mme Elena Rodica Ionescu Lebrun, Maîtresse de conférences
• Mme Marisa Manzano, Maîtresse de conférences
• Mme Emanuela Torelli, Maîtresse de conférences
• Mme Yanxia Hou-Broutin, Directrice de recherche
• Michel Federighi, Professeur

Supervised by

Jasmina Vidic