Preincubation Test to Rapidly Identify Post-Pasteurization Contamination in Milk and Single Cream

Area of Science:

• Food Microbiology
• Dairy Science
• Analytical Chemistry

Background:

• Post-pasteurization contamination is a significant concern for milk and cream safety.
• Accurate detection methods are crucial for ensuring dairy product quality and shelf-life.

Purpose of the Study:

• To evaluate a novel pre-incubation test for identifying post-pasteurization contamination in milk and single cream.
• To assess the test's accuracy in predicting microbial levels after refrigerated storage.

Main Methods:

• A pre-incubation test (P-INC test) using nisin, penicillin, and crystal violet was developed.
• Samples were incubated at 21°C for 25 hours, followed by storage at 6°C for 7 days.
• The test's predictive accuracy for contamination levels was determined for milk and cream.

Main Results:

• The P-INC test successfully predicted contamination levels in 85% of milk samples and 86.1% of cream samples.
• A Bacillus sp. resistant to the test inhibitors was isolated from cream samples.
• The presence of this resistant Bacillus sp. did not significantly impact the test's overall accuracy.

Conclusions:

• The P-INC test is a reliable method for detecting post-pasteurization contamination in milk and cream.
• This test can aid in quality control and safety assurance for dairy products.
• Further investigation into resistant organisms may be warranted for specific dairy matrices.