High-pressure processing effects on foodborne bacteria by mid-infrared spectroscopy analysis

• Gram-positive bacteria showed resistance to HPP, while Gram-negative were inactivated.
• Bacteria spectral profiles before and after HPP treatment are different.
• The decrease in the water signal may indicate cell disruption triggered by HPP.
• Changes in hydrogen bonds appear to be on the basis of the HPP-induced modifications.

High pressure processing is an emergent technology for food preservation that causes minimal changes in the characteristics of the foods, preventing food spoilage and foodborne diseases.In this work, 12 different foodborne bacteria were submitted to high pressure (300 MPa, 15 min, room temperature) in order to assess the bacterial reduction and the alterations induced with this processing in cellular components. It was observed that all the Gram-negative bacteria were inactivated to undetectable levels while Gram-positive showed resistance to pressure, being Staphylococcus aureus and Bacillus cereus the most resistant, decreasing only 2 logs. Listeria monocytogenes decreased about 5 logs. IR spectroscopy was used to investigate the differences in the spectra of the cells after the pressurization. Regarding cellular modifications, it was possible to notice that changes in hydrogen bounds appear to be on the basis of the modifications observed in the spectra after high pressure processing.