Question

The aseptic processing of milk is typically conducted at...........and it works on the preservation mechanism of ………..

• A. $138^\circ C$ 2‐3 sec, inactivation & restriction of microorganism
• B. $138^\circ C$ 2‐3 sec, inhibition of microbial growth & restriction of microorganism
• C. $72^\circ C$ 15 sec, inactivation & restriction of microorganism
• D. $72^\circ C$ 15 sec, inhibition of microbial growth & restriction of microorganism

Hint:

HTST ($72^\circ C$) = Pasteurized (requires fridge). UHT ($138^\circ C$) = Aseptic (Shelf-stable).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question focuses on UHT (Ultra High Temperature) processing, also known as aseptic processing, for milk. We need to identify the correct temperature/time combination and the underlying biological logic for shelf-life extension.

Step 2: Detailed Explanation:

• Aseptic Processing (UHT): This involves heating the milk to very high temperatures for extremely short bursts. The goal is to achieve commercial sterility with minimal damage to nutrients and flavor.

• Standard Conditions: The typical UHT range is $135^\circ C$ to $150^\circ C$ for 1 to 5 seconds. Option (A) gives a very standard specific set: $138^\circ C$ for 2-3 seconds.

• Mechanism:
• Inactivation: The heat is high enough to kill (inactivate) all vegetative cells and, crucially, bacterial spores.
• Restriction: After heating, the milk is cooled and packaged in sterile containers under "aseptic" conditions. This restricts the entry of any new microorganisms from the environment.
• Pasteurization (Option C/D): $72^\circ C$ for 15 seconds is the HTST (High Temperature Short Time) pasteurization standard. It kills pathogens but not all spoilage organisms or spores, which is why pasteurized milk requires refrigeration.

Step 3: Final Answer: UHT milk is processed at high heat ($138^\circ C$) to ensure microbial inactivation and then aseptically packaged to restrict further contamination.