Rapid methods for differentiating reactivated from residual phosphatase in milk and cream: collaborative study

Area of Science:

• Food Science
• Analytical Chemistry
• Dairy Science

Background:

• Phosphatase activity in milk and cream can indicate inadequate pasteurization.
• Differentiating reactivated from residual phosphatase is crucial for quality control.

Purpose of the Study:

• To collaboratively test methods for differentiating reactivated from residual phosphatase.
• To evaluate the efficacy of magnesium acetate versus magnesium chloride as reactivating agents.

Main Methods:

• Collaborative testing of three phosphatase detection methods: modified Scharer rapid test, rapid colorimetric test, and Rutgers method.
• Use of magnesium acetate and magnesium chloride for phosphatase reactivation.
• Testing of milk and cream samples by nine and sixteen collaborators, respectively.

Main Results:

• Magnesium acetate enhanced the accuracy of phosphatase reactivation compared to magnesium chloride.
• Visual methods (modified Scharer, Rutgers) were accurate for high phosphatase levels but less so in borderline cases.
• Integrating a photoelectric colorimeter with the modified Scharer rapid test significantly improved results.

Conclusions:

• The modified Scharer rapid test, particularly when enhanced with a photoelectric colorimeter, is a reliable method for detecting phosphatase activity.
• Magnesium acetate is a preferred reagent for phosphatase reactivation in dairy products.
• The modified Scharer rapid test was adopted as official first action based on these findings.