During the pet food recalls, many pet food owners wondered why the pet food companies did not test for melamine and melamine-related compounds in their ingredients. We asked ourselves would all of the recalls have been avoided and all of our pets’ lives been saved if they had included these in their testing?
How do the industry protein tests work? Traditionally, food protein is measured by a method developed by Danish brewer Johann Kjeldahl in the late 1800s. (Time for an updated test, perhaps?) In this method, a strong acid digests a sample which breaks down the organic matter and releases nitrogen. This is then converted to ammonia. This amount indicates how much nitrogen was in the original sample and, thus what is the amount of protein. One food scientist says this is a “robust, precise method.” This test can be used for a variety of products and protein types.
Another nitrogen-based technique called the Dumas test is popular with the industry. The method burns the sample to release nitrogen. The Association of Analytical Communities (AOAC) International lists the Kjeldahl and Dumas techniques as the standard methods for measuring protein in food.
The problem with these two nitrogen-based tests is that they assume that the nitrogen in food is protein constructed from nitrogen-based amino acids. This is fine if unadulterated food is being tested because the other major parts of food, carbohydrates and fats, do not contain nitrogen. Since the tests measure the total amount of nitrogen from both protein and nonprotein, they do not measure the true amount of protein.
This can make it easy to cheat the two tests. In the pet food recalls, nitrogen from melamine could not be distinguished from amino-acid nitrogen and contributed to the total protein in the sample.
From Scientific American:
Several alternative, non-nitrogen-based protein tests exist, such as laboratory chromatography and ultraviolet spectrophotometry, but they are expensive and time-consuming and require extracting protein from food, a process that differs depending on the type of food. For rapidly analyzing food protein, â€œprobably the best technique,â€ McClements says, is infrared spectroscopy, which relies on the peptide bonds in proteins absorbing infrared light in distinguishable ways. The method demands that each chemical to be screened first be run to calibrate the machine; if researchers are not looking for a particular chemical, they will not find it using infrared spectroscopy. The appearance of a nonprotein spike would indicate a possible contaminant in the sample that could then be identified through other tests.
The Canadian Grain Commission adopted near-infrared reflectance (NIR) technology, a type of infrared spectroscopy, for screening its grain supply some 30 years ago. Since then, the U.K., Australia, Russia and Argentina, among others, have also switched to NIR. More than 90 percent of wheat worldwide is screened with NIR, according to Phil Williams, a consultant at PDK Grain in British Columbia and an early adopter of the technology for use in the grain industry. In principle, NIR could measure protein in a variety of food types, including wheat gluten and rice protein concentrates.
Still, some doubt that NIR could economically replace the nitrogen-based tests. Carl Schulze, president of New Jersey Feed Lab, a Trenton-based company that analyzes food for industry, states that 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.
Thus far pet food makers and other processors have not decided whether to adopt new methods. â€œWeâ€™re in the process of building a feed safety protocol,â€ says Ron Salter, a vice president at feed distribution company Wilbur-Ellis in San Francisco. He adds that the company will be looking into feed sampling and testing procedures. In the meantime, nitrogen-based methods will likely remain top dog among protein-testing techniques.
For more analysis and opinions of the industry protein tests, here is a post on Itchmo forums from Offy, an Itchmo reader.