Pasteurizer Temperature Deviation in a Milk Plant
A cooperative dairy in Guwahati runs an HTST pasteurizer at 72 °C for 15 s. On 12 June, the recording chart shows that the holding-tube outlet fell to 69.5 °C for about 8 minutes during the morning shift; the flow-diversion valve had been placed in manual override because the actuator was sticking. About 4,000 L of toned milk was packed in 500 mL pouches during and after the deviation and 3,000 L had already been dispatched to retailers. The plant's HACCP plan identifies pasteurization as CCP-1 with a critical limit of ≥72 °C/15 s. The operator says the milk 'tasted fine' and the alkaline phosphatase test on a retained sample was negative. The plant wants to release the remaining 1,000 L after a second heat treatment at 75 °C/15 s.
1. Evaluate the CCP deviation and decide the disposition of the 1,000 L still in the plant and the 3,000 L dispatched. Justify with HACCP principles.
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A critical limit of ≥72 °C/15 s was not met: 69.5 °C for 8 min is a CCP-1 deviation. The manual override of the flow-diversion valve is itself a control failure, so product that passed during the deviation cannot be treated as pasteurized. Taste and a single negative alkaline phosphatase result are not sufficient release evidence; ALP is a verification/process indicator, and a negative result on one retained sample does not cover all packs or prove absence of pathogens. The 1,000 L should remain on hold; a second heat treatment at 75 °C/15 s may be considered only as a validated corrective action if the milk has been kept cold and is organoleptically acceptable, otherwise it should be condemned. The 3,000 L dispatched should be traced and recalled, with notification to the food safety authority. Release requires a documented risk assessment and HACCP reassessment, not operator judgement.
2. Identify root cause and corrective actions to prevent recurrence.
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The immediate root cause is the sticking actuator, but the system cause is the manual override: a CCP was allowed to operate without automatic diversion. Corrective actions: restore/repair the actuator; remove or lock out the manual override; interlock the diversion valve so product cannot flow forward below 72 °C; add an alarm and automatic recorder; verify the valve at start-up and after maintenance; calibrate the recorder and temperature sensor; retrain operators that override is not permitted; add a second-person check for CCP records. Also review the HACCP plan and maintenance schedule, because a known sticking actuator should have been a preventive maintenance item. The goal is to make the safe state the default, not to rely on operator vigilance.
3. What verification records would you examine to confirm the fix?
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Examine the pasteurizer recorder charts for the deviation and for the next 30 days; the flow-diversion valve function test before and after repair; the actuator maintenance work order and spare-part record; calibration certificates for the temperature sensor and recorder; alarm/interlock test records; operator training sign-off; and the HACCP record review. Also check alkaline phosphatase and microbiological results for product after the repair, mock recall/traceability records for the 3,000 L, and the corrective-action log. Verification is not a single test: the combination of engineering proof, records and product data must show the CCP is back in control. If any record is missing, the fix is not verified.