Question

Which of the following roles is not associated with indigenous enzymes in milk?

• A. Deterioration of milk/ products
• B. Antimicrobial effect
• C. Nutritional benefit
• D. Index of thermal history of milk

Hint:

Indigenous enzymes serve as indicators of pasteurization (alkaline phosphatase) and cause spoilage (lipase, plasmin), but they do not provide direct nutritional value to the consumer.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Milk contains numerous native (indigenous) enzymes synthesized by the mammary gland or transferred from the blood.
These enzymes play several biochemical, analytical, and technological roles in dairy science, though they do not serve a primary dietary function for the consumer.

Step 2: Detailed Explanation:
Let us examine the roles of indigenous enzymes in milk:
- Deterioration of milk/products: Active enzymes can degrade milk quality during storage.
For example, indigenous lipoprotein lipase hydrolyzes milk fat to release free fatty acids, causing hydrolytic rancidity.
Plasmin, an indigenous protease, degrades caseins, leading to bitterness and textural defects. Thus, this role is associated with milk enzymes.
- Antimicrobial effect: Some native enzymes provide protective, antimicrobial benefits.
Lactoperoxidase catalyzes the oxidation of thiocyanate by hydrogen peroxide to generate bactericidal hypothiocyanite ions.
Lysozyme hydrolyzes peptidoglycan in bacterial cell walls, directly lysing Gram-positive bacteria. Thus, this role is associated with milk enzymes.
- Index of thermal history: Because enzymes have specific thermal denaturation profiles, monitoring their inactivation helps verify heat treatments.
Alkaline phosphatase is used to confirm successful pasteurization, while lactoperoxidase serves as a marker for high-temperature pasteurization. Thus, this role is associated with milk enzymes.
- Nutritional benefit: Indigenous milk enzymes do not provide significant direct nutritional benefits to the consumer.
They are present in minor, non-nutritive quantities and are quickly inactivated by stomach acid and digestive proteases.
Therefore, nutritional benefit is not a recognized role associated with indigenous milk enzymes.

Step 3: Final Answer
The correct option is (C).