Question

Which of the following need to be added to milk to activate LP system ?

• A. Hydrogen peroxide
• B. Hydrogen peroxide and thiocyanate
• C. Lactoperoxidase enzyme
• D. Thiocyanate

Hint:

LP system = Enzyme (already present) + Thiocyanate + Hydrogen peroxide → antimicrobial action.

Answer 1

The Correct Option is B

Concept: The Lactoperoxidase (LP) system is a natural antimicrobial system present in milk. It helps in preserving milk by inhibiting bacterial growth, especially in raw milk under rural conditions.

Step 1: Components of LP system.
The LP system consists of three essential components:
• Lactoperoxidase enzyme (naturally present in milk)
• Thiocyanate ion (SCN$^-$)
• Hydrogen peroxide (H$_2$O$_2$)

Step 2: Activation condition.
Although lactoperoxidase is naturally present, the LP system becomes active only when:
• Thiocyanate and hydrogen peroxide are available in sufficient quantity

Step 3: Mechanism.

• Lactoperoxidase catalyzes the reaction between H$_2$O$_2$ and SCN$^-$
• Produces antimicrobial compounds (hypothiocyanite ions)
• These inhibit bacterial growth

Step 4: Evaluating options.

• Only hydrogen peroxide → Not sufficient
• Only thiocyanate → Not sufficient
• Lactoperoxidase → Already present
• Hydrogen peroxide + thiocyanate → Correct combination

Step 5: Conclusion.
Thus, both hydrogen peroxide and thiocyanate are required to activate the LP system.