Effect of Thermal Processing on Antibacterial Activity of Multifloral Honeys

In this study, the effects of thermal processing in the antibacterial activity of four multifloral honeys were determined. The thermal treatments were carried out at 30, 40, 50, 60, 70 and 80C, and the following characteristics were determined: total phenols and antibacterial activity of three gram‐positive bacteria (Bacillus subtilis, Staphylococcus aureus and Listeria monocytogenes) and three gram‐negative bacteria (Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa). The results showed that the behavior of total phenols in relation to temperature depended on the floral sources of honey. The honeys presented curves of either linear or quadratic responses of the antibacterial activity in relation to the thermal process, depending on the honey's floral sources and the kind of bacterium to inhibit. The results suggest that the honey's antibacterial activities and behavior with the temperature are different depending on the honey's floral sources and the kind of bacteria that they inhibit. PRACTICAL APPLICATIONS: The consumer trend to search for minimally processed foods has increased in recent years due to the perception that food processing decreases its health benefits and antibacterial activities. Honey can inhibit pathogenic bacteria, but this inhibition is determined by the floral source from which the honey is collected. In this study, it was shown that thermal processing has a different effect on the antibacterial activities of each honey. These effects were linear or quadratic according to the bacteria (Bacillus subtilis, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa) and the floral source of the honey. This effect did not depend on the Gram (the inhibition against Salmonella typhimurium was linear with respect to the thermal process in all honey), in contrast to E. coli (where the effect was quadratic with a peak at 60C in all of the honey). The results led to the conclusion that the thermal processing of each honey must be different to maximize their beneficial health effects as well as their antibacterial activities.