In this blog post, we’ll explore the mechanism of transglutaminase—a protein-binding enzyme used in molecular gastronomy—along with its various applications, safety concerns, and proper usage.
What Is Transglutaminase?
Molecular gastronomy is a culinary technique that scientifically harnesses the physical and chemical reactions between ingredients that occur during the cooking process. It is characterized by reconfiguring familiar ingredients into new textures and forms, offering unique sensory and visual experiences. For example, representative cases include foam-like sauces made with salt or scallop bacon rolls created using protein-binding techniques—these are examples of familiar ingredients being presented in entirely new forms.
Transglutaminase (TG) is an enzyme commonly referred to as “meat glue,” which serves to bind proteins together. Industrially used TG is primarily produced through microbial fermentation, and in nature, similar enzymes exist in animal tissues where they play a role in blood clotting and tissue formation. During the cooking process, it serves to bind separated protein structures together, a principle similar to re-solidifying crumbled tofu.
In the food processing industry, TG is used for a wide variety of applications. When added to yogurt, it makes the protein structure denser, increasing gel strength and reducing whey separation, thereby maintaining a smoother and more stable texture. In baking, it strengthens protein bonds within the dough to create a springy texture and helps maintain a stable structure during the baking process. As such, TG is an enzyme that plays a crucial role in improving the physical properties of food to enhance texture and quality.
TG is called a “protein adhesive” because it forms strong covalent bonds (isopeptide bonds) between the glutamine and lysine residues of protein molecules. Unlike carbohydrates or fats, proteins possess a structure that allows for such bonding; therefore, TG selectively binds proteins together to improve a food’s elasticity, viscosity, and texture. This mechanism is responsible for increasing the viscosity of yogurt and creating the chewy texture of bread. Furthermore, the covalent bonds formed in this way are relatively heat-stable and do not easily break down during typical cooking processes.
Another advantage of TG is that it has very little effect on the natural taste and aroma of ingredients. Therefore, even when applied to various food ingredients—including proteins—it can improve the desired texture without significantly compromising the original flavor, making it widely used in food processing and cooking.
However, since TG is an enzyme, its activation conditions are critical. Generally, at temperatures above approximately 60°C, enzyme activity decreases significantly or is inactivated, preventing it from performing its binding function. The binding time also varies depending on the ingredient and temperature. At refrigeration temperatures, sufficient time—typically at least 4 hours—is generally required, whereas at relatively high temperatures of about 50–55°C, binding can occur within tens of minutes. Actual application conditions vary depending on the type of food and the desired texture. For example, fish—which must retain its freshness—is often bonded at refrigerated temperatures over a sufficient period of time, while products with consistent manufacturing processes, such as dough or processed foods, can be bonded more efficiently under appropriate temperature conditions.
Applications and Controversies in Cooking and Industry
Molecular gastronomy restaurants in the United States and other countries are using TG to improve the texture and shape of ingredients or to introduce new dishes that were previously difficult to create.
A prime example is a method for making cod fillets: TG is evenly applied to the surface of the fillet, which is then rolled into the desired shape and thickness using plastic wrap. After allowing it to set under refrigerated conditions for a certain period, the fillet is cut into uniform-sized steaks. This process ensures that fillets of varying thicknesses and shapes are standardized, resulting in consistent cooking times, even distribution of seasoning, and a uniform quality in the finished dish.
Another interesting application is a technique for making noodles using only shrimp instead of flour. When TG is mixed into finely ground and kneaded shrimp, and the mixture is extruded in thin strands into water at approximately 55°C using a syringe or similar tool, the proteins bind together, allowing the strands to retain their noodle shape. This is one of the most representative attempts in molecular gastronomy to create a new type of pasta using seafood. However, since these cooking methods are highly influenced by various variables—such as the state and viscosity of the ingredients, the equipment used, temperature, and time—it is difficult to maintain consistent quality. Consequently, while they are utilized in some high-end restaurants or for research purposes, they have not yet become widely adopted as standard items on restaurant menus.
TG is widely used not only in high-end restaurants but also in the food processing industry. It is utilized in processes to produce meat products of uniform size or to mold cut meat into a single product, and it is also used to improve the texture of various protein-based foods, such as ham, sausage, chicken nuggets, fish cakes, and processed seafood products. In South Korea, there are also cases where TG is used in the manufacturing process of formed meat products. When used at the appropriate concentration, TG helps maintain a firm bond even after heating without significantly affecting the meat’s color, aroma, or flavor, thereby ensuring a consistent appearance and texture.
However, this technology must be accompanied by proper hygiene management. While the interior of whole cuts of meat generally does not come into direct contact with the external environment, the surface can be exposed to microorganisms during slaughter and processing. When multiple pieces of meat are bonded with TG, the parts that were originally the outer surfaces may end up on the inside; if the meat is not heated sufficiently in this state, pathogenic microorganisms present inside may survive, increasing the risk of food poisoning. For this reason, it is important to ensure that meat bonded with TG is thoroughly cooked to a sufficient internal temperature before consumption.
Another reason people have concerns about TG is the controversy surrounding the safety of the enzyme itself. To date, the U.S. Food and Drug Administration (FDA) and food safety agencies in Europe and other countries have evaluated microbial-derived transglutaminase used in food manufacturing as a safe food processing aid when used in accordance with approved standards and intended uses. Furthermore, to date, no cases of harm to the general public have been clearly confirmed. However, some studies have raised the need for further research into potential associations with specific diseases or effects on the gut microbiome, and related research is ongoing. Therefore, while TG is currently evaluated as a safe enzyme when used within approved limits and for authorized purposes, ongoing review of new research findings is also necessary.
Despite these technical and hygienic controversies, many chefs and food engineering experts view TG as just one of many culinary tools. Humans have long processed food ingredients using various scientific principles—such as fermentation, aging, smoking, salting, and emulsification—and TG is seen as one of the outcomes of the advancement of these food processing technologies. There is also the view that aversion to its chemical name does not necessarily correspond to actual risk. For example, the salt we use daily is chemically sodium chloride, but we do not judge its safety based on its name alone. TG, too, needs to be evaluated by considering both its intended use and regulatory standards.
Many believe that the reason the term “meat glue” has acquired a negative connotation in South Korea is not due to the technology itself, but rather because of reported cases where some businesses failed to provide consumers with sufficient information or properly adhere to hygiene standards. Every technology has both advantages and disadvantages depending on how it is used. Molecular cuisine and food processing technologies are likely to advance further in the future, and the scope of TG’s application may also expand across various fields. To reduce unnecessary misunderstandings about these technologies, it will be necessary to provide accurate scientific information, implement transparent labeling systems, ensure thorough hygiene management, and maintain continuous oversight and supervision of relevant regulations.
