The idea of eating a steak made from pieces of meat scrap glued together is likely to stick in the craw for most people. But there are also those who are ready to shell out a small fortune at New York’s uppity WD-50 restaurant for a chance to sink their teeth into “shrimp noodles” concocted with the same “meat glue.”
So, what is this “meat glue?” Rest assured that no horses were condemned to the glue factory to produce it. What we’re talking about is an enzyme called transglutaminase that allows a mouthful of shrimp to be served in the form of noodles that look, but certainly do not taste, like regular pasta. How does it do this? By facilitating a chemical reaction that forges links between structural protein molecules. Proteins of course are composed of chains of amino acids, and transglutaminase links the amino acid lysine in one chain to glutamine in an adjacent chain. If these chains are located on the surface of adjacent pieces of meat, the pieces get stuck together almost like magic. The joint then looks just like one of the white streaks of gristle or fat commonly seen in meat. It’s so strong that the meat doesn’t even tear along the “fault line.”
Transglutaminase is not foreign to the human body. We produce it to aid in blood clotting, a process that requires protein molecules to form interlinked complex structures. Skin and hair are also composed of proteins that have been bound together, and transglutaminase plays a role here as well.
In the 1990s, the food industry discovered that this enzyme can be isolated in good yield from the bacterium Streptoverticillium mobaraense and that it can be used to “restructure” meat, fish and poultry. For example, with the help of transglutaminase, bits of chicken left over after the carcass has been processed, instead of being discarded as waste, can be glued together to produce chicken patties. Similarly, artificial crab legs and shrimp can be made by sticking together ground pieces of cheaper seafoods such as Pollock. While the taste of such artificial foods can be criticized, there is no health issue associated with consuming transglutaminase. As any other protein, it is readily broken down into its component amino acids in the digestive tract.
“Meat glue” is produced for the food industry under the name Activa by the giant Japanese company Ajinomoto which also markets monosodium glutamate (MSG). It did its work quietly behind the scenes until celebrity chef Heston Blumenthal brought it out of the shadows at the Fat Duck, the restaurant on the outskirts of London that has been labeled by many as the best eating place in the world. Blumenthal’s enthusiasm for creating novel dishes with transglutaminase rubbed off on Wylie Dufresne at New York’s famed WD-50 restaurant who managed to grind shrimp into noodles with the help of transglutaminase and served it on a bed of smoked yogurt.
Other chefs who pursue what has been called “molecular gastronomy,” defined as the application of scientific principles to the creation of new dishes, are pushing the transglutaminase envelope. Around the corner are filet mignon with strips of bacon glued to its surface, fish coated with chicken skin to enhance flavour and shrimp burgers held together by cross-linked proteins. How about chicken fat stuck to steak to add a new dimension to chicken fried steak? Just in case your cholesterol isn’t high enough.
Unfortunately transglutaminase also lends itself to some less savory applications. Such as producers or butchers using it to bind meat scraps too small to be sold into slices that look every bit as delectable as prime cuts. The seamless joints are virtually undetectable. Ditto for any difference in taste. Just take the bits of meat, sprinkle them with transglutaminase, place them on a sheet of plastic wrap and roll tightly into the shape of a tube. Refrigerate for a few hours and then unwrap. You’ll be looking at meat that for all the world looks like a single piece of filet. And it can be priced accordingly.
Clearly there is deception involved here. The customer is not getting what he or she is paying for. There are some other issues as well. Transglutaminase can be isolated from blood, with bovine and pig blood being used commercially. This can be a problem for people adhering to religious dietary laws. Not only can transglutaminase be used to make “restructured meat,” it can also be used to improve the texture of hot dogs and sausages. Meat glue is not allowed in Europe, but can be used in Canada as long as it is declared on the label like any other additive. For example, if Chicken McNuggets were glued together with this enzyme, it would have to be listed on the ingredients list, which is available from McDonald’s. It’s not. So no “meat glue” there. Whether or not some unscrupulous butchers use it to make fake steaks, is another matter.
Any butcher engaging in such clandestine operations may pay a price. While ingesting transglutaminase is no problem, inhaling the powder can damage the lungs. Consumers don’t have to worry about this, but there is an issue with cooking glued meat. The surface of meat is always covered with bacteria but the microbes are readily killed by cooking. However, with structured meat, some of the outside becomes the inside, and if the meat is not thoroughly cooked, as is of course possible for people who like their steak rare, bacteria on the inside may survive. This is the reason why hamburger meat, a classic “outside becomes inside” situation, has to be cooked through and through.