UNIVERSITY PARK, Pa. -- The sticking point when it comes to the current furor over the use of products given the unappetizing name "meat glue" by critics of the food industry, is labeling, according to a meat expert in Penn State's College of Agricultural Sciences.
Operators of meat-processing plants, out of necessity, adhere to a strict policy of accuracy when it comes to listing ingredients in products, said Edward Mills, associate professor of dairy and animal science. In facilities inspected by the U.S. Department of Agriculture, truth in labeling is very serious business.
"In the current jargon, what is being called 'meat glue' is not a processing aide, but is an ingredient," said Mills, who teaches food science courses on the science and technology of meat, poultry and seafood. "If enzymes are used as binding agents, they must be listed on the label."
He explained that in a USDA-inspected plant, the labeling is reviewed by a government inspector, and the operator is not likely to risk being charged with fraudulent labeling. "The operator could face not only a product recall or having his plant shut down, but he could go to jail if he intentionally omitted ingredients from a label."
"Meat glues" -- generally two different products known by the trade names Activa or Fibrimex -- commonly are used to connect pieces of fresh meat to make more uniform, attractive servings. Activa, Mills said, is a white powder form of a natural protein cross-linking enzyme called transglutaminase.
The transglutaminase enzyme is found naturally in many biological systems, including the human body. The commercial form of transglutaminase, marketed as Activa, is derived from a microorganism. Fibrimex is a natural protein cross-linking system derived from pig or beef blood. Its natural function is to coagulate or clot blood in response to injury.
"In theory, you could use this stuff to reassemble any pieces of meat into a larger piece," he said. "But the reality is that there are only certain products where it is economically feasible to use it because it is fairly expensive. What is being called 'meat glue' largely is being used to make portion-controlled, fresh-meat cuts."
As examples, he cited the binding of beef or pork tenderloins. Because these pieces of meat have irregular shapes, connecting two together results in cuts yielding slices that are more uniform and attractive.
"One use that has found pretty wide acceptance is the making of what we call restructured or reformed filet mignon," Mills said. "A tenderloin at one end is large and round but tapers to a wide, flat shape. So what is done with some frequency is to take to two tenderloins, turn one around and apply Activa powder to the surface.
"Then the two cuts are put together, wrapped with plastic for few hours or overnight until the transglutaminase enzyme in Activa forms cross-links between the two protein surfaces. The result is a long cylinder of tenderloin that is the same dimension and shape from one end to the other -- yielding nice round slices of filet mignon."
Mills noted that a similar process is conducted with turkey breasts, which are notoriously irregular in shape. Generally these products are being sold in the restaurant, food-service and institutional markets, where uniformity of shape is very important, he said.
But meat glue is not used in boneless hams or most cold cuts, Mills stressed. Reports that meat glue is found in up to a third of products such as bologna and luncheon meats are wildly inaccurate, he contended.
"There are many restructured meat products available on the market, but the vast majority are formed using the natural tendency of the muscle to re-adhere due to protein coagulation upon cooking," he said.
"So essentially all boneless hams -- which are restructured products that consist of meat pieces bound together -- don't include meat glue, but rather salt-soluble protein as a binding agent that is extracted from the meat surface during a process called massaging, or tumbling."
There is one aspect of the debate about meat glue and restructured meats that Mills suggests is important for consumers to understand, and that is adequate cooking. Restructured meats should be cooked thoroughly -- like hamburgers and not like steaks -- which makes it critical that cooks and chefs read the labels and know the difference.
"When a meat such as filet mignon is reassembled or reformed -- when part of the surface becomes the center -- microorganisms are trapped inside," he said. "So it is really important that you be aware of what you're cooking and cook it appropriately."
Mills advises against cooking restructured meats to a very rare degree of doneness. He said such products still may be cooked to medium-rare (defined by USDA as 145 degrees Fahrenheit) safely, but they must be held at that temperature for four minutes before serving.
"When a chef or cook chooses to use restructured, fresh-meat cuts, he or she should adjust cooking procedures and make sure that others in the kitchen are aware of those changes to avoid the risk of foodborne infection," he said.