Potential for the Low-Temperature Pasteurization of Dairy Fluids Using Membrane Processing

Area of Science:

• Food Science
• Microbiology
• Chemical Engineering

Background:

• Membrane processing is crucial for dairy product safety and quality.
• Understanding bacterial retention is vital for effective microbial control in dairy streams.

Purpose of the Study:

• To evaluate bacterial retention by various membrane filtration systems.
• To assess the impact of membrane type, unit design, and dairy fluid composition on microbial removal.

Main Methods:

• Dairy fluids (raw milk, skim milk, whey) were processed using microfiltration and ultrafiltration membranes from different manufacturers.
• Inoculation with specific bacteria (Staphylococcus aureus, Salmonella typhimurium, Pseudomonas fragi) and presence of indigenous microorganisms were studied.
• Permeate and retentate streams were analyzed for bacterial counts and total solids; temperature and pressure were controlled.

Main Results:

• No membrane process completely retained bacteria while allowing all solids to permeate.
• Spiral wound microfiltration and ultrafiltration membranes achieved 98.9% to 99.99% bacterial load reduction in permeate.
• Dissimilar bacterial retention was observed between membranes of the same molecular weight cut-off; unit design influenced retention.
• Bacterial morphology and size did not significantly affect retention; fluid composition had minimal impact.

Conclusions:

• Low-temperature membrane processing significantly reduces, but does not eliminate, microorganisms in dairy permeate.
• Effective bacterial removal is achievable with microfiltration and ultrafiltration, though complete sterilization is not reached.
• Optimizing membrane selection and unit design is key for maximizing bacterial retention in dairy processing.