Pasteurization is done at _______________.

Correct Answer: C. 63 degree Celsius for 30 minutes

Pasteurization is a low-temperature, long-time (LTLT) heat treatment designed to reduce pathogenic microorganisms in milk and other beverages without significantly altering nutritional or sensory properties. The standard pasteurization temperature is 63°C for 30 minutes, which effectively inactivates most vegetative pathogens (including Mycobacterium tuberculosis, Salmonella, Listeria, and Coxiella burnetii) while preserving milk quality. This combination of temperature and duration is based on thermal death time (TDT) kinetics—the relationship between temperature and exposure time needed to achieve a defined log reduction in microbial load. At 63°C, 30 minutes provides sufficient time for heat penetration and microbial inactivation without causing excessive protein denaturation or fat oxidation. This method is widely used in Indian dairy industry and is the standard referenced in public health and food microbiology textbooks. The LTLT method contrasts with high-temperature, short-time (HTST) pasteurization (72°C for 15 seconds), which is faster but requires specialized equipment. For NEET PG, the 63°C/30 min standard is the classic definition that must be memorized.

Why the other options are wrong

A. 63 degree Celsius for 30 seconds — This is wrong because 30 seconds is insufficient exposure time at 63°C to achieve adequate microbial kill. While the temperature is correct, the duration is 60 times shorter than required, resulting in incomplete inactivation of heat-resistant pathogens like Coxiella burnetii. This appears to confuse LTLT pasteurization with HTST (which uses higher temperature but shorter time). NBE traps students who remember only the temperature component. B. 73 degree Celsius for 20 minutes — This is wrong because 73°C is intermediate between LTLT and HTST standards, and 20 minutes is neither the standard LTLT duration (30 min) nor the HTST duration (15 sec). This temperature-time combination is non-standard and does not correspond to any recognized pasteurization protocol in Indian dairy guidelines. NBE uses this as a distractor for students who guess by mixing parameters from different methods. D. 72 degree Celsius for 30 seconds — This is wrong because 72°C for 30 seconds approximates HTST pasteurization (72°C/15 sec is the standard), but 30 seconds is too long for true HTST and too short for LTLT. Students confuse this with the correct HTST standard. The question specifically asks for pasteurization (implying LTLT), not the faster HTST variant. This is a classic NBE trap pairing two different methods.

High-Yield Facts

Mnemonics

LTLT vs HTST Low Temperature Long Time = 63°C/30 min | High Temperature Short Time = 72°C/15 sec. LTLT is the classic 'pasteurization' standard; HTST is modern dairy shortcut. 63-30 Rule When you see 'pasteurization' without qualifier → think 63 and 30 (temperature in °C, time in minutes). This is the NEET PG standard.

NBE Trap

NBE pairs HTST (72°C/15 sec) with LTLT parameters to create plausible-sounding distractors (e.g., 72°C/30 sec, 73°C/20 min). Students who know only one method or confuse temperature with duration fall into these traps. The question tests whether you know the exact LTLT standard, not just the concept.

Clinical Pearl

In Indian dairy supply chains, LTLT pasteurization (63°C/30 min) remains the gold standard for small-scale and cooperative dairies because it requires minimal equipment and preserves milk's nutritional value—critical for populations relying on milk as a primary protein source. HTST is reserved for large commercial operations. Knowing this distinction is essential for public health and food safety questions in NEET PG.

_Reference: Jawetz, Melnick & Adelberg's Medical Microbiology Ch. 3 (Sterilization & Disinfection); Park's Textbook of Preventive & Social Medicine Ch. 7 (Food Hygiene)_