Paper I — 2023 July (Supplementary) (2010 Scheme) — Q8
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Paper I
2023 July (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Pasteurisation.
Q82 marksShort Notes
Answer
Pasteurization is a moist-heat process that kills pathogenic and most spoilage microorganisms in a liquid (classically milk) using a temperature and time combination well below 100°C — sufficient to destroy vegetative pathogens while preserving the nutritive/organoleptic quality of the product; it is disinfection, not sterilization (spores and some heat-resistant organisms survive).
Methods:
Holder (batch) method — 63°C for 30 minutes.
Flash (HTST) method — 72°C for 15–20 seconds; the most widely used commercial method.
Ultra-High-Temperature (UHT) method — 135–150°C for a few seconds, giving a longer shelf-life product.
Organisms targeted: primarily milk-borne pathogens such as Mycobacterium bovis (historically the key target organism), Salmonella, Brucella, Coxiella burnetii, and Listeria monocytogenes.
Verification: the phosphatase test — alkaline phosphatase, naturally present in raw milk, is destroyed by adequate pasteurization; a positive phosphatase test after processing indicates inadequate/failed pasteurization.
