Food microbiology — Batch (holder) method of milk pasteurization: at what standardized temperature–time combination is the milk held to ensure pathogen reduction while preserving quality?

Introduction / Context:
Pasteurization is a controlled heat treatment that significantly reduces pathogenic and spoilage microorganisms in milk without markedly affecting its nutritional and sensory qualities. Two classic protocols exist: the batch (holder) method and the high-temperature short-time (HTST) method. This question focuses on the precise temperature–time setting for the batch method used in small dairies, research labs, and artisanal processing.

Given Data / Assumptions:

• The process in question is the batch (holder) method, not HTST or UHT.
• Time–temperature pairs are standardized to achieve equivalent microbial lethality for typical milk pathogens.
• Milk is the matrix; target organisms include Coxiella burnetii and Mycobacterium spp., among others.

Concept / Approach:
Pasteurization lethality is a function of temperature and time. For the batch method, milk is heated to a moderate temperature and held long enough to reach the required log reduction in pathogens. The canonical standard pair for the holder method is 63°C held for 30 minutes, which provides adequate thermal lethality while minimizing quality loss compared with higher temperatures or prolonged heating.

Step-by-Step Solution:

Verification / Alternative check:
Regulatory and dairy technology texts consistently list 63°C for 30 minutes for the holder method; HTST is 72°C for 15 seconds; UHT is typically 135–150°C for 2–10 seconds for commercial sterility (not pasteurization).

Why Other Options Are Wrong:

• 72°C for 60 seconds: resembles HTST temperature but the standard hold time is 15 seconds, not 60.
• 73°C for 30 minutes: excessive heat load for holder method, risking quality degradation.
• 72°C for 6 minutes: not a recognized standard for milk pasteurization.

Common Pitfalls:
Confusing holder with HTST and assuming any higher temperature equals better pasteurization; standards are validated time–temperature pairs, not arbitrary combinations.

Final Answer:
63°C for 30 minutes