High-acidity tanker at a village chilling centre
A village dairy cooperative receives 4,200 L of pooled morning milk in four tankers. The chilling centre has a plate chiller, a pasteuriser rated at 500 L/h, a cream separator and a 200-L paneer vat. Tanker 3, carrying 900 L, shows 0.21% lactic acidity, 3.5% fat, 8.0% SNF and a positive starch-iodine test; it arrived at 11:00 instead of 07:00. Tankers 1, 2 and 4 show 0.15% acidity and normal fat and SNF. The cooperative market milk standard is acidity not above 0.16% and no added starch. The plant has no incubator, only a milkotester and a thermometer. The manager must decide within an hour because the evening route starts at 16:00. The cooperative chairman wants to mix tanker 3 with the rest so that nothing is wasted.
1. Evaluate tanker 3 and decide whether it can be blended into the market milk supply.
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Tanker 3 fails two independent standards: acidity is 0.21% against a maximum of 0.16%, and the starch-iodine test is positive, indicating added starch or a deliberate thickener. Blending 900 L into 3,300 L would give an average acidity of about 0.163%, still above the standard, and would not remove the adulterant. The positive starch test alone makes the milk unfit for market milk. The decision is to reject tanker 3 as market milk, retain a sample under seal, inform the supplier and the chairman in writing, and not mix it with tankers 1, 2 and 4. The 11:00 arrival also explains bacterial growth and acidity rise, so the rejection is technically sound. If the cooperative wants to use it, it must be condemned for human consumption as adulterated milk, not converted into paneer or curd for sale.
2. How should the 3,300 L of acceptable milk be handled given the pasteuriser capacity and the 16:00 route?
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At 500 L/h, 3,300 L needs 6.6 hours of pasteuriser time, so starting at 12:00 would finish at 18:36, too late for a 16:00 dispatch. The practical plan is to chill all acceptable milk immediately to 4°C, then pasteurise in two streams: run 2,000 L from 12:00 to 16:00 for the evening route, and hold the remaining 1,300 L chilled for the next morning. Alternatively, divert 500 to 800 L to the paneer vat if the cooperative has a confirmed buyer, because paneer can absorb milk that cannot reach the route on time, but only from acceptable milk. Do not shortcut the pasteuriser holding time. Record batch times and temperatures, and pre-cool the pasteuriser before the first run. If the evening route cannot be delayed, the chairman must choose between a shorter route with 2,000 L and cold storage for the rest.
3. What preventive and record-keeping measures should follow this incident?
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Introduce tanker-wise sampling at receipt, with acidity, fat, SNF and starch tests recorded before unloading. Set a fixed 07:00 delivery window and apply a late-arrival penalty; investigate why tanker 3 arrived four hours late. Train suppliers on clean milk production, especially cleaning of cans and immediate chilling. Keep a sealed sample from every tanker for 24 hours, and maintain a rejection register with supplier name, quantity, test results and signature. The laboratory should be upgraded with a simple incubation facility or tie-up with a district laboratory for confirmatory tests. Review the chairman's proposal in a cooperative meeting so that the rejection is treated as a quality decision, not a personal one. Finally, calculate the loss from 900 L and compare it with the cost of a small bulk milk cooler and stricter route scheduling.