Photodynamic inactivation of Pseudomonas fluorescens in Minas Frescal cheese using curcumin as a photosensitizer

The dairy industries demand innovative technologies for food preservation and elimination of psychrotrophic bacteria like the Photodynamic Inactivation of Microorganisms (PDIM) modalit, which is based on the generation of reactive oxygen species using photosensitizers. The objective was to determine in vitro the phototoxic potential of Curcumin (CUR) solubilized in different media against Pseudomonas fluorescens. In Minas Frescal cheese inoculated with Pseudomonas fluorescens, CUR acted as an antimicrobial agent and photosensitizers when incorporated in an edible and biodegradable coating. The coatings were characterized in terms of mechanical properties and permeability. The cheeses were evaluated on days 0, 3, 6, 9 and 12 by microbiological, physical-chemical and mechanical analysis. The efficiency of PDIM was influenced by solubilizers and concentrations of CUR, observing the synergistic effect of CUR with irradiation. Dimethyl sulfoxide and ethanol were the solubilizers that allowed greater CUR phototoxic activity and reduced 7 log CFU/mL of Pseudomonas fluorescens, the main spoilage bacteria in milk and dairy products. In cheeses, the photoinhibition of microorganisms was hampered by the complexity of the surface. The samples treated with CUR showed lower bacterial count and proteolysis, and consequently, greater hardness. Therefore, PDIM can be an alternative technique for use in dairy products.