Inhibitor-Assisted High-Pressure Inactivation of Bacteria in Skim Milk

Area of Science:

• Food Microbiology
• Food Processing Technology
• Food Safety

Background:

• Bacterial contamination in skim milk poses a significant food safety challenge.
• Conventional preservation methods may impact milk's nutritional and sensory qualities.
• Exploring novel inactivation strategies is crucial for enhancing milk safety and shelf-life.

Purpose of the Study:

• To investigate the combined efficacy of high hydrostatic pressure (HHP) and antimicrobial compounds (potassium sorbate, ε-polylysine [ε-PL]) against common bacterial pathogens in skim milk.
• To assess the impact of these combined treatments on skim milk quality attributes.
• To evaluate the potential of synergistic HHP and antimicrobial treatments for milk preservation.

Main Methods:

• Skim milk inoculated with Escherichia coli, Salmonella enterica Typhimurium, Listeria monocytogenes, and Staphylococcus aureus.
• Application of high hydrostatic pressure (500 MPa for 5 min) alone and in combination with potassium sorbate or ε-PL (2 mg/mL).
• Bacterial enumeration, scanning electron microscopy for cell damage assessment, and milk quality analyses (color, turbidity, protein -SH groups, in vitro digestion).

Main Results:

• HHP (500 MPa, 5 min) significantly reduced bacterial populations to <1 log CFU/mL.
• Combined HHP with potassium sorbate or ε-PL achieved greater bacterial inactivation than HHP alone.
• No regrowth of E. coli, S. enterica Typhimurium, or L. monocytogenes was observed during 15 days of refrigerated storage with HHP + ε-PL.
• Synergistic treatments induced significant bacterial cell wall damage.
• Combined treatments did not adversely affect milk color, turbidity, protein -SH groups, or in vitro digestion.

Conclusions:

• The combination of high hydrostatic pressure with potassium sorbate or ε-polylysine offers a synergistic approach for effective bacterial inactivation in skim milk.
• These combined treatments provide enhanced microbial safety without compromising essential milk quality parameters.
• HHP combined with antimicrobial agents presents a promising strategy for the preservation of milk and milk-based products.