Effect of interactions of plant phenolics with bovine meat proteins on their antibacterial activity

The activity of 5 phenolics totally inhibiting the growth of Staphylococcus aureus CNRZ3 at a 1 g L−1 concentration in Mueller-Hinton broth for 24 h incubation at 37 °C was reevaluated at 37 °C for 24 h, 15 °C for 6 days, or 6 °C for 8 days in the presence of up to 20% (w/w) bovine meat proteins to mimic the temperature of refrigerated storage of bovine meat and its protein content, respectively. These changes affected in a different way the antibacterial activity of the 5 phenolics. Isobutyl-4-hydroxybenzoate kept its bactericidal activity, while naphthazarin was bactericidal at 6 °C and 15 °C but not at 37 °C in the presence of bovine meat proteins. Gallocyanin was bactericidal at 37 °C up to a 5% (w/w) protein content in the medium but not at 15 °C or 6 °C. Resveratrol and chrysin always lost their bacteriostatic activity when bovine meat proteins were added. The partition coefficient at 6 °C of each phenolic between a 20% (w/w) bovine meat extract suspension with and without proteins was determined. The antibacterial activity reduction of phenolics in the presence of bovine meat proteins was correlated with their affinity for bovine meat proteins.