Monday, April 30, 2007

Tainted Wheat Gluten Update

I was patting myself on the back for tracing the source of the tainted wheat gluten to Binzhou, in Shandong.

There was one element that I got wrong: how and why the melamine got into the wheat gluten.

I argued that melamine was a relatively expensive petrochemical, and it didn’t seem logical from a cost-benefit point of view to use it as filler in wheat gluten.

The New York Times argues quite persuasively that cheap melamine scrap was routinely ground up and added to Chinese feed ingredients to inflate the measured protein content and obtain a higher sales price.

Protein is a difficult component to measure. Protein content is therefore measured indirectly by decomposing the protein’s constituent amino acids to release their nitrogen content. The amount of protein is inferred by recovering and measuring the amount of nitrogen recovered and multiplying that number by a factor reflecting the proportion of nitrogen to the overall amino acid molecule.

The nitrogen-to-protein multiplier for the most commonly used protein measurement procedure, the Kjeldahl test, is 6.25. So one mg of added nitrogen would translate into 6.25 mg of perceived protein.

Melamine is a nitrogen-rich chemical that would be likely to disassociate during the harsh Kjeldahl process—which includes an acid wash—and produce elevated protein results.

The process is extremely laborious and a little bit dangerous, involving digestion, distillation, and titration. Certainly no ordinary farmer could perform it, and the test is probably widely honored in the breach inside China.

Inflating protein content to rip off gullible farmers is a long and honored tradition around the world.

I’m most familiar with the scam of spiking feed ingredients with bone and feather meal from a rendering plant. This meal is proteinacious, but nutritionally useless—the protein is denatured and can’t be absorbed. But adding the meal does allow the supplier to claim a higher protein content—and price.

Since I wasn’t aware of the protein angle for melamine, I proposed that the melamine might have made its way to the wheat plant as contamination in the water supply.

That premise looks like it was waaaaaaaaaay off.

However, I do take some consolation in the fact that the New York Times visited the Mingshui Chemical Plant—which I had identified in my post as the likely source of melamine since it was just upriver from Binzhou--and found that it was a source of the scrap melamine that was auctioned off once per quarter and is apparently finding its way into the local feed industry.

The interesting investigatory issue will involve the nature of the testing that the U.S. importers performed when the Chinese material was received.

Did they perform Kjeldahl tests?

Were there other tests they should have reasonably conducted to detect melamine or other contaminants?

Did the U.S. importers blend the Chinese material—a common precaution to dilute whatever nasties were inside the imported protein materials and also, perhaps, allow the importer to claim U.S. origin for the stuff—or did some companies take the rather reckless step of sending their pet food customers 100% Chinese material?

An interesting story.

Also, a story that the Chinese government—for the sake of its credibility and for the health of its citizens and livestock—should not continue to cover up.

10 comments:

Chinalawblog said...

Thanks for the update

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