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Testing for protein … and gaming the system
By Gina Spadafori
July 15, 2007
Good read from Scientific American on how the food industry test for protein (thanks, Offy!):
Regardless of whether its addition was deliberate or accidental, melamine snuck past standard industry protein analysis, suggesting that the century-old test methods should be reevaluated. Several alternatives exist, but the food industry has yet to make a switch.
Traditionally, food protein is measured by a method developed by Danish brewer Johann Kjeldahl in the late 1800s. In this analytical technique, a strong acid digests a sample, breaking down the organic matter and releasing nitrogen, which is then converted to ammonia. The amount of ammonia indicates how much nitrogen was in the original sample and, hence, the amount of protein.
[...]
The nitrogen-based methods may be tried, but they are not entirely true. They assume that the source of all nitrogen in food is protein constructed from nitrogen-based amino acids. This assumption is reasonable if unadulterated food is being analyzed, because the other major components of food—carbohydrates and fats—do not contain nitrogen. But because the tests detect total nitrogen, from both protein and nonprotein alike, they do not truly measure protein.
Hence, any chemical rich in nitrogen can potentially trick the Kjeldahl or Dumas test. In the pet food scandal, nitrogen from melamine was indistinguishable from amino-acid nitrogen and contributed to the tally used to calculate the protein in the sample.
Here’s the rest.
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Good to see the scientific community writeing more about this issue. I hope that scientists continue to contribute articles and educate people.
Thanks scientists, please feel encouraged to write more.
Comment by Rose L — July 15, 2007 @ 11:44 am
Gina, is this something that our Congresspersons need to hear? If there are specific tests that could assist in protecting our food supply (human/companion animals), that would be something to fight for in new legislation. The internet has articles about dairy milk being tested for “true protein” by methods other than the Kjeldahl test so that only usable milk protein is paid for (profit motive initiated the switch in testing methods, I assume). http://extension.usu.edu/dairy.....ruprot.htm
What testing methods would be better based on your knowledge?
Comment by shadepuppy — July 15, 2007 @ 12:01 pm
Darn! The article that you linked to states:
“…Still, some doubt that NIR could economically replace the nitrogen-based tests. …NIR works best when one type of feed is being tested repeatedly. But the high initial cost of setting up the machine and running samples that are similar to the products being tested means that the technique may not be a viable alternative for the independent laboratories that test the food supply…”
Doesn’t seem likely that pet food companies would find it economically feasible to make that switch in testing (although it could have saved them a ton of lost revenue [and saved lives] if they had used the test this spring. Sounds like you still have to “know what you’re testing for” also, although the testing for milk protein in the other article seemed to suggest that labs could see a discrepancy between total and usable protein — which could lead to further testing to find out WHAT else is in the product. I hope there is some lab method that can alert people to the presence of some “non-food” substance and require examination to determine its identity.
Comment by shadepuppy — July 15, 2007 @ 12:13 pm
It’s amazing how easily misinformation goes down when a phd is added to an author’s name. To date, there isn’t a speck of evidence tying melamine to the 30% increase in pet deaths due to kidney failure in the 3 months prior to the announcement of the pet food recall. On the contrary, 40 years of melamine research has shown the substance to be virtually nontoxic at amounts 10 times the highest level found in any pet food sample. In one study, dogs were fed food with melamine at 30,000 PPM for a full year with no ill effects. That compares to the 3,000 PPM the FDA has reported as being the highest level found in any pet food sample tested.
Testing for NPN (non protein nitrogen) is widely available and runs about a hundred bucks a pop. The author points out that testing is typically used on grain. Why is that? The reason is ruminants, such as cattle, are able to use NPN as a protein source. The problem is they can only use so much of the stuff before their bodies convert too much of it to ammonia, which can kill them. This chemical process does not take place in non ruminants, such as people and dogs, but people and dogs are not able to use NPN as a protein source. Right here in the good old US of A, cyanuric acid and urea are approved for use in ruminant feed. Melamine is used for that purpose in other places, but as I’m sure some of us know, some US companies have used it for that purpose for years.
So, the question is, after we cut through the smoke and mirrors of Doctor Huff and Puff, is why don’t pet food companies use the cheap and widely available tests for NPN? The obvious answer is they don’t have to test to know it’s there, because they make a regular practice of adding it to the food to fake the results. Perhaps they were miffed that the same hoax they’ve been playing on us was played on them.
The bottom line is there are no escape clauses in the laws intended to protect our food supply, which hold the manufacturers liable for insuring that no adulterated food product leave their factories for sale to the public. Additionally, the second another company slaps their own label on the can, they are held to the same level of responsibility as the actual manufacturer.
Let’s ignore the inanities put forth by the likes of Doctor Huff and Puff, and instead focus on the real issue. In the last 4 years, at least a dozen dangerous or deadly pet food recalls have been announced. Not once has a criminal indictment been prosecuted against any of the companies legally responsible, in spite of the fact that announcing a recall is on its face an admission of criminal acts.
The only new thing we need is aggressive enforcement of existing laws, in holding criminals responsible for criminal acts.
Comment by Don Earl — July 15, 2007 @ 12:52 pm
Is the recall is going on or not?
Comment by jill — July 15, 2007 @ 5:29 pm
Not in the minds of the FDA, PFI and most consumers.
Animals continue to get sick and unexpected substances are still showing up in foods that haven’t been pulled off the shelves.
Don, thanks for that analysis. There are probably studies that show that productivity would actually be higher if animals weren’t eating chemicals and being raised in massive feedlots. (There are comparable analyses for grains).
Comment by shibadiva — July 16, 2007 @ 4:32 am