Functionalization of Food Packaging with Active Antimicrobial Agent

This thesis shows the results of a research process focussed in developing antimicrobial food packaging. The surface of food-grade polyvinyl chloride (PVC) is functionalized with antimicrobial agents, with the goal of extending the shelf-life of fresh products. Surface functionalization is an effective strategy for imparting antimicrobial properties to food-grade polymeric packaging. The study employs a range of surface-sensitive techniques, such as X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), to verify the effectiveness of the functionalization process. PVC was successfully functionalized with two antimicrobial agents: polyhexamethylene guanidine (PHMG) and 4-(10,15,20-triphenylporphyrin-5-yl)-aniline (TPPA). Initially, PVC is treated with (3-mercaptopropyl) trimethoxysilane (MPTMS), followed by 3-(aminopropyl)triethoxysilane (APTES) and glutaraldehyde. These layers facilitate the bonding of PHMG and TPPA through interactions between carbonyl and amino groups. Successful functionalization was confirmed using ATR-FTIR. The interpretation of the XPS/ARXPS results posed a challenge due to the presence of signals from C atoms in both the substrate and the functional layers. To address this issue, gold was utilized as a C-free substrate to optimize the C 1s curve fitting. This approach enabled the differentiation between the PVC substrate and the functional layer. The thickness of the functionalization layers from the ARXPS data suggested the formation of complex structures upon functionalization with glutaraldehyde and PHMG. Additionally, AFM and SEM revealed changes in the surface morphology. P-PVC exhibited promising antimicrobial activity against S. aureus and E. coli in Sardinian food samples and has significant antimicrobial potential for food packaging materials.