Browsing by Author "Carrasqueiras, Miguel Fernandes"
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- Development of functional films based on antimicrobial photodynamic inactivationPublication . Carrasqueiras, Miguel Fernandes; Crugeira, Pedro; Barreiro, FilomenaMicrobial contamination remains a major food safety challenge, requiring innovative and sustainable control strategies beyond traditional thermal or chemical methods. Antimicrobial photodynamic inactivation (aPDI) has emerged as a promising alternative, based on the activation of photosensitizers that induce the formation of reactive oxygen species (ROS) capable of eliminating microbial cells. In this work, κ-carrageenan-based functional films incorporating curcumin solid dispersions at 1% and 5 wt% concentrations, designated CF_1%_1Y and CF_5%_1Y, were evaluated as photoactive systems for food applications. The solid dispersion approach improved the stability, amorphization, and homogeneous distribution of curcumin in the hydrophilic polymeric matrix. The FTIR and DSC analyses confirmed the preservation of the polymer network and the amorphous state of curcumin. The absorption spectrum at 445 nm, characteristic of curcumin, was identified by UV-Vis spectrophotometry. Evaluation of the mechanical properties demonstrated the structural integrity and strength of the CF_5%_1Y film, yielding a tensile modulus of 196.5 ± 15.6 MPa, a tensile strength at break of 3.22 MPa, and a strain at break of 4.03%. In planktonic cells, CF_5%_1Y under LED irradiation (450 ± 10 nm), at an energy density of 100 J/cm², reductions of 99.9% for Escherichia coli and 96.7% for Listeria monocytogenes were achieved, confirming the synergistic action of light, oxygen, and curcumin in ROS generation. Decontamination tests performed on cream cheese and mayonnaise matrices confirmed the antimicrobial properties of aPDI, previously identified in planktonic cells. When using irradiated CF_5%_1Y films, microbial reductions of 98.5% for E. coli and 99.4% for L. monocytogenes were observed in the mayonnaise matrix. In contrast, in cream cheese, reductions reached 91.2% for E. coli and 92.8% for L. monocytogenes. In 15-day preservation tests, samples of mayonnaise and cream cheese with irradiated CF_5%_1Y films maintained the integrity of the food matrices, with constant microbial concentrations of 1.7-1.8 log CFU/g. At the same time, the controls showed increased contamination, reaching approximately 4.3 log CFU/g in mayonnaise and 2.3 log CFU/g in cream cheese. These results demonstrate the effectiveness of functionalization and photoactivity, corroborating the development of stable, efficient, and sustainable films with antimicrobial properties for food decontamination and preservation, offering an eco-friendly path.