A new decontamination method for Bacillus subtilisin pasteurized milk: Thermosonication treatment

Area of Science:

• Food Science and Technology
• Microbiology
• Biotechnology

Background:

• Conventional thermal processing faces challenges with heat-resistant microorganisms.
• Thermosonication (TS) offers a novel alternative for food decontamination.
• Extending the shelf life of pasteurized milk while maintaining quality is a key industry goal.

Purpose of the Study:

• To evaluate the efficacy of Thermosonication (TS) combined with High-Temperature Short-Time (HTST) pasteurization.
• To assess the decontamination effect on Bacillus subtilis in milk.
• To investigate the impact of HTST-TS treatment on milk quality and shelf life.

Main Methods:

• Comparative analysis of HTST pasteurization versus HTST-TS treatment.
• Microbiological enumeration of Bacillus subtilis.
• Assessment of bacterial cell membrane permeability and integrity using DNA/protein leakage and Transmission Electron Microscopy (TEM).
• Enzyme activity assays (ATPase, SDH, MDH).
• Physical and chemical analyses of milk (L* value, zeta potential, particle size).

Main Results:

• HTST-TS treatment significantly reduced Bacillus subtilis by over 4 log CFU/mL in both medium and milk.
• Increased DNA and protein leakage observed in the HTST-TS group, indicating cell membrane damage.
• TEM confirmed bacterial cell wall rupture and content leakage in the HTST-TS group.
• Significant inhibition of bacterial enzymes ATPase, succinate dehydrogenase (SDH), and malate dehydrogenase (MDH) was noted.
• HTST-TS treatment improved milk's L* value, zeta potential, and colloidal particle size without affecting oral sensitivity.

Conclusions:

• HTST-TS is a viable and effective decontamination method for pasteurized milk.
• This combined treatment enhances milk quality and extends shelf life by targeting bacterial integrity and enzymatic activity.
• The findings support the implementation of HTST-TS in the dairy industry as an advanced processing technique.