Thursday, July 15, 2010


What passes through your mind when you see the word 'milk'? A tall, cold glass of creamy goodness. For many, milk plays a big part in everyday lives, whether they are children and adults.

A yummy glass of milk.

In November 2008, milk took the spotlight internationally in an unexpected way- tens of thousands of infants were reported to be sickened by the consumption of melamine-tainted milk formula. Most were hospitalized for severe kidney failure and kidney stones, 4 were reported dead. People from all over the world were horrified by the incidents and most of all by the culprit- melamine. So what exactly is melamine? How did it end up being added into milk products?

Disposal of contaminated baby milk formula.

Melamine is an organic base which is most commonly found in the form of insoluble white crystals. It is a trimer of cyanamide, with a 1,3,5-triazine skeleton.

Molecular structure of melamine.

Skeletal structure of melamine.

In the early production days, melamine is synthesized by first converting calcium cyanamide into dicyandiamide, and then heated to form melamine. Now, however, urea is used to commercially produce melamine with the following reaction:
6(NH2)2CO → C3H6N6 + 6 NH3 + 3 CO2

There are two steps involved in the reaction. First off, urea is decomposed into cyanic acid and ammonia:
(NH2)2CO → HCNO + NH3

Secondly, the cyanic acid formed polymerizes to form melamine and carbon dioxide:
6 HCNO → C3H6N6 + 3 CO2

The decomposition of urea is an endothermic reaction, while the polymerization of cyanic acid is exothermic. Overall, it is an endothermic process.
Melamine as a solid, white powder.

Melamine is combined with formaldehyde to produce melamine resin, which is widely used to make plastic products, adhesives, dishware, fabrics, countertops and dry-erase boards. Its high-nitrogen content enables it to have fire retardant properties, as it releases nitrogen gas when it comes into contact with flames. Sulfonated melamine formaldehyde (SMF) is a polymer used as cement admixture to make high-resistant concrete.

Melamine resin plate ware.

In the 1950s, melamine was introduced to the farming industry as a fertilizer, also because of its nitrogen content. However, it was considered economically impractical as it was more expensive to produce and the nitrogen takes far longer to be mineralized and absorbed by plants. Later on, it was used as ‘non-protein nitrogen’ in cattle feed as a substitute source for protein. In 1978, however, studies concluded that it ‘may not be acceptable ‘, due to its slow and incomplete hydrolysis.

In China, water had been added to raw milk so that the volume would be increased. As a result, the milk is diluted and thus has a low protein concentration. Companies which use the milk for further processing and production, such as manufacturing powdered infant formula and diet milk, would routinely check the raw milk’s protein level through a test that measures the nitrogen content. Milk with protein levels that are below par would be rejected. To cope with that, melamine was added to the raw milk increase the nitrogen content of the milk, and therefore its apparent protein content. Standard tests, such as the Kjeldahl test or Dumas test, estimate protein levels by measuring the nitrogen content, and the addition of melamine is done to mislead the tests so that the milk would be acceptable.
Ingestion of melamine causes bladder stones. When combined with cyanuric acid, melamine can form crystals that cause the formation of kidney stones. This will contribute to kidney failure and, ultimately, bladder cancer.

One of the victims of melamine-contaminated milk.

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