More On Pet Food Additives

Weeks after the pet food recall that stunned and frightened dog and cat owners across America, the FDA is pursuing a theory that the imported ingredients used in recalled pet food may have been intentionally spiked with an industrial chemical to boost their apparent protein content.

A second pet food ingredient, rice protein concentrate, has been found in the U.S. to be contaminated by melamine. Previously, testing revealed that wheat gluten also had been contaminated.

As new details emerge about the origins of the food's contaminants, the list of recalled pet foods continues to lengthen. But also growing are the reasons for the individual recalls — manufacturers are blaming everything from salmonella to toxins.

More than 100 brands of pet food have been recalled.

The U.S. Food and Drug Administration has received more than 14,000 reports of pet illnesses so far. Officials have confirmed just 16 deaths but believe the actual number could be higher.

What is wheat gluten?

Wheat gluten is what remains when a dough made from wheat flour is washed and kneaded until its starch is rinsed away so that only the wheat's gluten remains. Wheat gluten is a popular meat substitute in Asia and in some Western markets. It is sometimes sold under its macrobiotic name, Seitan.

Wheat gluten is used for binding and serves as a protein source in some pet foods.

Although the United States is a major producer of wheat (and the world's largest wheat exporter), it produces little wheat gluten, preferring to import it from Europe, Australia or China. According to Slate.com, the U.S. is the world's biggest consumer of wheat gluten due to its widespread use not only as a meat alternative and in pet food, but because it is used in many baked goods.

A less expensive protein-heavy ingredient than soy or whey, rice protein is also less likely to be an allergen than the other products. It has been growing in popularity lately as a protein additive to foods, including pet food.

Companies producing the concentrate say it is also likely cheaper than many of the proteins on the market.

The concentrate is derived from wholegrain brown rice, and uses the entire rice kernel in the processing (in which natural enzymes digest the kernel's carbohydrates, leaving the protien.

Melamine is a chemical both associated with fertilizers and plastics, though it is neither alone. Combining it with formaldehyde can produce a durable resin that is used in housewares and other products in which plastic and plastic coatings are found. It can also be used as a cleaning product.

The FDA reported finding melamine in certain pet food last month — and found it in crystalline form in the urine of ill animals. Once in an animal's body, melamine can cause harm to the kidneys, though it is usually not considered a toxic ingredient. The U.S. government has banned the import of wheat gluten from China, suspecting a link between the melamine sometimes used in fertilizers in Asia and the wheat gluten imported from China.

The wheat germ importer maintains that none of the tainted product made it into the human food supply.

So far, melamine's been found in both wheat gluten and rice protein concentrate imported from China. Media reports from South Africa suggest a third pet food ingredient, corn gluten, used in that country also was contaminated with melamine. That tainted ingredient has not been found in the United States, according to the FDA, which is maintaining a pet food recall website with advice for worried pet owners.

It is possible that the tainted wheat gluten that triggered the pet food recall also ended up in processing plants used for food consumed by humans, the FDA said, according to an April 3 report published in the Boston Globe. Despite assurances that the human food supply is safe, "agency leaders" cannot "completely rule out contamination of human food by the suspect wheat gluten," the Globe reported.

The good news: Even if it turns out gluten contaminated with melamine was used in human food, it is unlikely the contaminant would pose a serious health risk.

Check out the National Library of Medicine's Hazardous Substances databank for more on melamine.

Read a Q&A about the recall.

Report animal illnesses or deaths to the FDA.

For more general information about the recall, click here.

A complete list of the recalled products, along with product codes, descriptions and production dates, was posted online by Menu Foods and is available at the Menu Foods Web site. The company also designated two phone numbers that pet owners could call for information: (866) 463-6738 and (866) 895-2708.