Challenge testing the lactoperoxidase system against a range of bacteria using different activation agents

Area of Science:

• Food Science
• Microbiology
• Biochemistry

Background:

• The lactoperoxidase (LP) system is a natural antimicrobial mechanism found in milk.
• LP requires hydrogen peroxide (H2O2) and a thiocyanate (SCN(-)) or halide (e.g., iodide, I(-)) to exert its activity.
• Garlic extract has been explored as a potential activator for the LP system.

Purpose of the Study:

• To evaluate the efficacy of three different LP activation systems on bacterial growth and milk quality.
• To compare the antimicrobial activity of LP+SCN(-)+H2O2, LP+I(-)+H2O2, and LP+garlic extract+ethanol.
• To assess the impact of these systems on key keeping quality (KQ) indicators in milk.

Main Methods:

• Three LP activation systems were tested against Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus cereus in sterilized milk.
• Bacterial growth was monitored over time at optimal growth temperatures for each organism.
• Keeping quality indicators including pH, titratable acidity, ethanol stability, and clot on boiling were measured.

Main Results:

• The LP+I(-)+H2O2 system eradicated all tested bacteria, with no detection for 35-55 hours, maintaining milk quality.
• The LP+garlic extract+ethanol system showed minimal effect on P. aeruginosa but slightly retarded growth and extended KQ by 5-10 hours for other organisms.
• The LP+SCN(-)+H2O2 system demonstrated intermediate effects, causing significant inhibition and extending KQ by 10-15 hours, with temporary regrowth observed in P. aeruginosa.

Conclusions:

• Iodide is a highly effective activator for the LP system in milk, providing robust and sustained antimicrobial action.
• Garlic extract shows limited potential for activating the LP system for significant antimicrobial benefits in milk.
• The LP+SCN(-)+H2O2 system offers moderate antimicrobial activity, with varying efficacy depending on the bacterial species and potential for synergistic or antagonistic interactions.