Question

Pasteurized milk does not contain which of the following enzyme:

• A. Plasma lipase
• B. Alkaline phosphatase
• C. Xanthine oxidase
• D. Membrane lipase

Hint:

Alkaline phosphatase is the "indicator enzyme" for milk pasteurization. If it's gone, you can be confident the pathogens are gone too. The phosphatase test is a standard quality control check in dairies.

Answer 1

The Correct Option is B

Step 1: Understand the purpose of pasteurization. Pasteurization is a heat treatment process designed to kill pathogenic microorganisms. It also inactivates several native enzymes present in raw milk.
Step 2: Identify the key indicator enzyme for pasteurization. The heat treatment conditions for pasteurization (e.g., 72\(^\circ\)C for 15 seconds for HTST) are specifically designed to be slightly more severe than what is required to destroy the most heat-resistant pathogen commonly found in milk, {Coxiella burnetii}. Conveniently, the native milk enzyme alkaline phosphatase has a similar heat resistance. Therefore, the absence of active alkaline phosphatase is used as a reliable indicator that pasteurization has been successful. The other enzymes listed are more heat-stable and may survive the process.