Ghee with high free fatty acids and excess moisture
A cooperative dairy separates 20,000 L of cow milk at 4% fat. The cream is standardized to 40% fat, held for 48 hours at 10°C, churned, and the butter is held for 18 hours at 18°C before ghee making. The butter is melted and boiled at 115°C for 60 minutes in an open jacketed kettle. The batch yields 780 kg ghee. Analysis: moisture 0.65%, free fatty acids 1.8% as oleic acid, and a rancid, slightly bitter flavour. The plant's ghee specification is moisture ≤0.5% and FFA ≤0.5%; the cooperative wants to sell the batch as standard ghee. The dairy officer must decide whether to release, reprocess or downgrade it and what caused the high FFA and moisture.
1. Carry out a fat balance for the batch and comment on the yield and losses.
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Fat in the milk = 20,000 L × 4% = 800 kg fat.
If the cream is standardised to 40% fat and all the fat is recovered, the cream quantity is 800/0.40 = 2,000 kg. Butter at about 82% fat would be 800/0.82 = 976 kg. Ghee at about 99.5% fat would be 800/0.995 = 804 kg theoretical yield.
The actual yield is 780 kg, which is 780/804 × 100 = 97.0% of the theoretical fat yield. The shortfall is about 24 kg of fat, or 3%. Some loss is normal in buttermilk, ghee residue and filtration, but 3% is on the high side and should be investigated. Check the churn efficiency, the buttermilk fat, the ghee residue fat and any spillage or scorching in the open kettle. The calculation also shows that the high FFA is not a yield problem alone: the batch still contains most of the fat, but that fat has been damaged by lipolysis.
2. Explain the likely causes of the high FFA and the high moisture, and say whether the batch meets the plant specification.
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FFA: 1.8% as oleic acid is well above the plant limit of 0.5%. Free fatty acids come from lipase action on milk fat. The cream was held for 48 hours at 10°C, which is too warm and too long for raw cream; lipase remains active and continues to release butyric and other short-chain acids. The butter was then held for 18 hours at 18°C, another warm holding step. The result is the rancid, slightly bitter flavour described. Copper or iron contact can accelerate oxidation, but the FFA itself is a lipase problem.
Moisture: 0.65% exceeds the 0.5% specification. In an open kettle, moisture removal depends on boiling time, surface area and settling. The butter may have been transferred with too much buttermilk or wash water, and the ghee may not have been allowed to settle and decant cleanly. Fine residue can also hold moisture. Boiling at 115°C for 60 minutes should normally drive moisture below 0.5%, so the result suggests either incomplete settling, foaming or a moisture-rich residue.
Conclusion: the batch fails both the FFA and moisture specifications. It cannot be released as standard ghee.
3. What disposition and preventive measures do you recommend?
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Disposition: hold and segregate the batch. Do not release it as standard ghee and do not blend it with good ghee to dilute the FFA; that would be a deceptive practice and the rancid flavour would still be detectable. Neutralising the FFA with alkali is not an acceptable ghee-making step-it can produce soapy flavours and is not a permitted way to bring a damaged batch to standard. If the cooperative has an approved downgraded outlet, use it only after a documented quality decision; otherwise condemn the batch.
Preventive measures: cool the separated cream rapidly to 4°C or below and churn within 24 hours; do not hold raw cream for 48 hours at 10°C. Cold-store butter at about 4°C, not 18°C, and shorten the holding time. Avoid copper or iron contact. Melt and clarify under controlled conditions, allow proper settling, decant or filter the ghee, and check moisture before packing. Use opaque, airtight containers and store away from light and heat.
Monitoring: test FFA and moisture on every ghee batch, and investigate any cream or butter holding period that exceeds the schedule. The FFA result is a direct warning about raw-material handling, not just a laboratory number.