Molecule of the Day

The pet food recall scare continues unabated; a couple weeks ago, people were pointing at aminopterin, a folic acid analogue, which was covered here. Now, people are pointing fingers at melamine as a potential contaminant.

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Melamine is a pretty simple compound, with a number of uses. Here, it’s being reported that it’s used as a fertilizer, which contaminated some wheat gluten, which ended up in the pet food. Despite the fact that you mostly get carbohydrate from wheat flour; gluten is actually a pretty inexpensive protein source. It’s mostly eaten in Asia, but some vegans have picked it up over here; if you’ve ever eaten seitan, that’s the stuff. You can actually make your own – just take some flour, a little salt, and enough water to make a yeastless bread dough. Keep playing with it under running water, and, eventually, you’ll be left with mostly gluten. Note that contamination is believed to be to blame, not gluten itself.

Melamine isn’t particularly toxic, but it has been implicated in kidney problems, which have been noted in the affected animals.

Melamine can also be polymerized with formaldehyde and sodium bisulfite, producing a very hard polymer (if you’ve ever used “melmac” plates, this is the stuff. It’s analagous to Bakelite plastic.

If polymerizing melamine resin is blown, you end up with a very light, fire-retardant foam with pores on the order of tens of microns across. The first two characteristics – weight and fire retardation – make it useful in airplanes and cars.

Awhile back, some people using melamine foams noticed that the combination of a hard plastic in a finely-textured foam made a pretty good cleaning product. If you’ve ever used “Magic Eraser” type products, this is what they are. It’s pretty amazing how the combination of water and the right abrasive can remove pretty much anything (including paint from walls, I note with some frustration).

Comments

  1. #1 _Arthur
    April 5, 2007

    How do you imagine the contamination happened ?
    I imagine not in the field, urea or melamine is unlikely to be concentated in the grain.

    Did someone managed to store gluten in an unwashed melamine silo ???

    If melamine costs more than gluten, which is likely, it makes no economic sense to drop melamine in gluten flour, to increase its bulk.

  2. #2 Molecule of the Day
    April 5, 2007

    Melamine finds use as a fertilizer; I think the idea is that it’s just a nitrogen-rich molecule (like urea or ammonia) that somehow ended up on the finished product (rather than being assimilated in protein, where it is blameless).

    The Time article actually has a significant error;

    Melamine is also used in human food such as baked goods and meat substitutes, but there is no indication the tainted wheat gluten has made it into human food.

    Here, “melamine” should be “Wheat gluten.”

    Note that polymerized melamine is safe; it’s found in containers used for food (“melmac”). Bakelite and melamine resin both are prepared with formaldehyde, too, which would be toxic if not in the copolymer. If this is true, this has to be melamine (not melamine resin) on or in the food (maybe surface contamination at some point, etc).

    The uses of melamine for fertilizer and for plastics are two different things; once you polymerize melamine, it’s not a toxic small molecule anymore; it’s part of a polymer.

  3. #3 _Arthur
    April 5, 2007

    Yes, I agree that urea or a similar nitro fertilizer is a more likely culprit than melamine.
    Time has a new article:
    http://www.time.com/time/nation/article/0,8599,1607483,00.html

    Richard Goldstein, associate professor of medicine at Cornell University College of Veterinary Medicine, who is part of a Cornell team investigating the cause of death, says he would not normally expect melamine to kill a pet. Research on melamine’s effects on animals is very limited: only a few dated studies have been done on dogs and just one on cats, which showed limited poisonous effects and no kidney damage. And melamine has a very low level of toxicity to rodents. “It looks like it [the melamine] is causing direct cell death in the kidneys and this is not something we would have expected to happen,” says Goldstein. “I don’t think it’s pure melamine. Maybe there is some kind of reaction with the metabolism of melamine that would cause this.”

  4. #4 Gibbon1
    April 5, 2007

    “How do you imagine the contamination happened ?”

    My bet would be that somehow wheat seed ended up being processed into wheat gluten. AKA someone got a ‘good deal’ on wheat seed mixed with melamine, that went off for some reason.

  5. #5 Uncle Al
    April 6, 2007

    Melamine is an inorganic chemical – not a single C-H or C-C bond anywhere. See what happens when pesky inorganikers are allowed to dump waste?

    Cats are primary carnivores. They evolved small livers because fresh kill terrestrial meat is never toxic. An acetaminophen tablet (N-acetylquinonimine metabolite) or a piece of chocolate (phenethylamine) can kill a cat. Dogs being omnivores evolved larger more competant livers because almost all plants are toxic (e.g., carotatoxin in carrots). Chocolate can kill dogs. One wonders how much contaminated Chinese gluten made it into human food products.

  6. #6 A
    April 6, 2007

    Yeah, urea is also inorganic, but for some reason it’s hailed as the “first organic compound to be synthesized.” Whatevah.

  7. #7 _Arthur
    April 8, 2007

    The wikipedia entry of melamine say:
    Melamine is a metabolite of cyromazine, a pesticide. It is formed in the body of mammals who have ingested cyromazine. It was also reported that cyromazine is converted to melamine in plants.

    http://www.fao.org/ag/AGP/AGPP/Pesticid/JMPR/Download/92/Cyromazi.PDF

    So now we went from rodenticides to fertilizers to pesticides. What a ride !

  8. #8 Wavefunction
    April 8, 2007

    Not only that, melamine forms some nifty supramolecular synthons with cyanuric acid, a classic system.

  9. #9 _Arthur
    April 9, 2007

    According to a FAO study, the insecticide cyromazine is metabolized by plants into melamine. Still the study attributes a low toxicity potential to melamine

    http://www.fao.org/ag/AGP/AGPP/Pesticid/JMPR/Download/92/Cyromazi.PDF

    “Residues of melamine were in many cases of the same order as those of cyromazine. At the CCPR in 1991 and 1992 some delegations were concerned that melamine was not included in the residue definition. The 1990 JMPR decided not to include melamine mainly because it is considered to be less toxic than cyromazine. ”

    “The available toxicological data base indicates that melamine is of no toxicological concern at the levels present in food or feed.
    Melamine is also a metabolite of prometryne. ”

  10. #10 Renan (Renan_s2)
    April 11, 2007

    Yeah, urea is also inorganic, but for some reason it’s hailed as the “first organic compound to be synthesized.” Whatevah.

    As I understand it, when Urea was synthesized, the definition of “organic compound” was “compound found in living things”, not “compounds containing carbon”.

  11. #11 Debbie
    April 20, 2007

    Interestingly, cyromazine is the active ingredient in feed through fly control products for horses. It is metabolized inside the horse and excreted in manure as melamine which interferes with the development of the fly larvae. Odd to be recalling pet food with melamine and yet it is being intentionaly fed to horses. Curious whether it has any ill effects in horses, or barn dogs that often eat horse manure, or people that use the manure in gardens?

  12. #12 Frank Sagevsal
    April 25, 2007

    The melamine contamination appears to be an adulteration, a deliberately added substance. Why add melamine to wheat protein? A fast test for protein is the nitrogen content, melamine boost nitrogen content, though not protein content. So if you had low grade protein and wanted it to appear to be high grade protein, add some melamine. Guess what it’s probably in the food chain as well, hope your kidneys are strong.

    Thanks FDA for doing a superb job of protecting the American people once again. Fun fact, the F in FDA stands for Food, which means our food safety falls under their perview, have you noticed a ban on Chinese wheat,rice and corn imports yet?

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