Tag Archive for: glutamate

Making Fake Meat Real: How Scientists are Tricking Your Tongue

Fake meat is often associated with a tough, flavorless texture that is added to dishes to provide protein. However, fake meat is no longer just glutinous balls or tofu hidden beneath sauces. From plant protein derived meats to in vitro preparations, there is much more to synthetic meat than what meets the tongue.


Veggie Sausage. Photo Credit: (Heather Quintal/Flickr)

Replicating meat texture

Meat texture is very complex. Consider the multiple components from muscle tissue fibers, blood vessels, fat, gristle, to nerves. Each component confers a different texture and flavor profile, so replicating meat is quite a challenging process.

Texture plays a big role in determining whether a product tastes like real meat or not. For example, the satisfyingly stringy texture one gets from pulling apart chicken strips. Fortunately, food scientists have found ways to emulate the fibrous quality in fake meat using soy protein. Soy protein is initially globular, so it must be denatured, or broken down, to make it more fibrous. Soy protein is first exposed to heat, solvent, or acid, before it is reshaped with a food extruder [1]. Extrusion processes are useful as they can form meat analogs with fibrous matrices, which can then be rehydrated into meat like substances [2]. However, this process can sometimes result in a dry product. The rising company Beyond Meat has gone further and found a way to use soy flour, pea flour, carrot fiber, and gluten-free flour to emulate the fibrous quality in their fake meat with a wet extrusion process. The proteins are realigned and then locked in position by crosslinking to get a fibrous chicken imitation that is also moist and juicy [1].

Taste & color of meat

The flavors of meat mostly arise during the cooking process. Maillard reactions between sugar and amino acids produce those familiar meat flavors and aromas [3]. The amino acid glutamate is of utmost importance as it activates the umami taste receptors. Real meats contain glutamate as it is found in proteins, and it is released during proteolysis that occurs during meat aging and cooking [4]. Since most fake meats do not contain glutamate, this taste can be added back with soy sauce, tomatoes, mushroom, and cheese in the form of sauces [5]. Another unique aspect of meat is its color. The myoglobin proteins found in muscle are initially red due to heme pigments, but with the added heat of cooking, protein denaturation results in a brown color associated with cooked meat. For fake meat, food colorings and spices can be used to mask the original color.

In vitro meat: your steak from a petri dish

To minimize the number of animals slaughtered, some scientists are even growing animal tissue in the lab [3]. To do this, they take a small muscle tissue sample and look for skeletal muscle satellite cells, which are essentially individual stem cells that are normally used to create new tissue in case of damage. After these satellite cells are collected, they are bathed in a nutrient serum where they can be coaxed into growing. When large enough, they are shocked with an electric current, which causes the tissue to contract and thicken, resembling small fillets of meat a couple centimeters long and a few millimeters thick [3]. While meat products generated using this process are not available at your local supermarket (or butcher), and this product is not truly “meat-less” for vegetarians or vegans, it could potentially maximize meat production by saving cows from the slaughterhouse.

In vitro meat samples. Photo Credit (Janique Goff/Flickr).

In vitro meat samples. Photo Credit (Janique Goff/Flickr).

Fake meat efforts are attracting big investments from Bill Gates and Silicon Valley entrepreneurs, as the demand for meat increases. In fact, population growth and a boost in meat consumption have increased the global demand for meat threefold in the last 40 years [6]. Not only does this intensify the requirements for raising livestock, but it also increases the greenhouse gas emissions emitted during processing [6]. It is no wonder that the search for the best meat-replication process continues on! Whether from an animal or plant base, synthetic meat is becoming increasingly prevalent and is not just for vegetarians and vegans anymore.

References cited:

  1. How ‘fake meat’ is made. Mother Nature Network.
  2. Riaz, Mian N., Anjum, Faqir M., Khan, Muhammad Issa. “Latest Trends in Food Processing Using Extrusion Technology.” The Pakistan Society of Food Scientists 17.1 (2007): 53-138. Web.
  3. Fake meat: is science fiction on the verge of becoming fact? The Guardian.
  4. The Chemistry of Beef Flavor. BeefResearch.org.
  5. What Foods are Glutamate-Rich? Msgfacts.org.
  6. The Bill Gates-backed company that’s reinventing meat. Fortune.

Catherine HuAbout the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

Read more by Catherine Hu


Understanding Umami

Imagine taking a bite of your favorite food. Is it sweet? Salty? Does it have a sour bite or a hint of bitterness? Maybe even a touch of savory umami?

Every time we eat, our taste buds sample these five basic taste qualities. Taste receptors decorating the surface of each taste bud interact with specific molecules; the corresponding flavor sensation then gets sent to your brain. Umami receptors, for example, sense the molecule glutamate. When free glutamate in our food—either naturally occurring or from added MSG—interacts with an umami receptor, we taste a delicious savory flavor.

Although glutamate is the primary source of umami flavor, certain molecules called nucleotides can enhance the umami sensation. Because nucleotides make up the genetic material (DNA and RNA) of all living things, nucleotides are ubiquitous in many of the foods we eat. Nucleotides themselves cannot activate umami taste receptors, but they can intensify the umami sensation caused by glutamate. Intrigued by this phenomenon, scientists Ole Mouritsen and Himanshu Khandelia recently published a paper exploring how one nucleotide, guanosine-5ʹ-monophosphate (GMP), might work together with glutamate to activate umami taste receptors.

Only one of the three known umami taste receptors can interact with both glutamate and GMP. This so-called “T1R1/T1R3” receptor switches between two states: an “off” state when no glutamate is present and an “on” state when glutamate is attached to the receptor. To understand how GMP might affect these two states, Mouritsen and Khandelia ran a series of computer simulations testing the receptor’s behavior in the presence or absence of GMP. As expected, glutamate caused the receptor to exist in the “on” state more than the “off” state. When GMP was added to the simulation, both GMP and glutamate interacted with the receptor to further stabilize the “on” state.

Model of the T1R1/T1R3 umami taste receptor. The taste receptor (in blue) is “off” when no glutamate is present. Glutamate interacts with the receptor, stabilizing the “on” state and signaling an umami taste sensation. Glutamate and GMP together bind the receptor and further stabilize the “on” state, presumably leading to a longer, more intense umami sensation.

Besides providing a compelling molecular model for umami taste sensation, this and future work on taste receptors may help us become more savvy seasoners in the kitchen. Because umami taste receptors are similar to the taste receptors for sweet and bitter, understanding how molecules like GMP enhance umami sensations can help us develop enhancers for other taste sensations. Just as GMP makes glutamate taste more intensely umami, a sweet enhancer could make sugar taste sweeter with no added calories. Identifying more taste enhancing molecules like GMP could bring a whole new dimension to the way we cook in the future. Forget about salt and pepper—the flavor enhancers are coming.

ProfileImageSmallAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

Read more by Liz Roth-Johnson

Chemophobia & The Myth of MSG


Chemistry professor Michelle Francl challenges our culture of chemophobia, while Harold McGee addresses some common misconceptions about “Chinese restaurant syndrome” and MSG. Read more

Umami Burger

If you have ever enjoyed the savory flavor of soy sauce or the rich, full flavor of Parmesan cheese, then you have experienced the taste sensation known as umami. The term “umami” was first coined in 1908 by Dr. Kikunae Ikeda to describe the unique savory taste of seaweed broth [1,2]. Although umami was initially associated only with Asian cuisines, researchers all over the world have now established umami as one of the five basic taste groups [3].

In his original study of umami, Dr. Ikeda isolated the amino acid glutamate from dried seaweed and found that this molecule was sufficient to create a strong umami flavor [1]. As an amino acid, glutamate is an important component of proteins and occurs naturally in all living things. When it is not incorporated into a protein, “free glutamate” can readily bind to glutamate receptors in our taste buds to trigger the umami taste sensation [4]. Despite their different names, glutamate, glutamic acid, and monosodium glutamate are essentially the same molecule and behave the same way in our bodies.Glutamate

Since the original discovery of glutamate, scientists have identified additional molecules that contribute to the umami taste sensation. The nucleotides inosine 5ʹ-monophosphate (IMP) and guanosine 5ʹ -monophosphate (GMP) are responsible for the umami taste of bonito and shiitake mushrooms, respectively [5]. Because nucleotides make up our genetic material, molecules like IMP and GMP are ubiquitous in living organisms. Interestingly, IMP and GMP alone do not have strong umami flavor but can synergistically enhance the umami sensation of glutamate [4,6].

Practically all living things contain the umami molecules glutamate, GMP, and IMP. Proteins are built from amino acids like glutamate, whereas the genetic molecules DNA and RNA are made up of nucleotides like GMP and IMP. More specifically, GMP is an important component of RNA, including the “messenger RNA” (mRNA) that is transcribed from DNA and subsequently translated into proteins. IMP is not a typical component of mRNA, but is instead incorporated into other types of specialized RNA molecules like “transfer RNA” (tRNA). Free IMP can also be derived from the energy molecule ATP. Although all living things contain GMP and IMP, free GMP is found predominantly in mushrooms, while free IMP is found mainly in animal products [7].

Although glutamate is most notoriously used as a flavor-enhancing food additive in the form of MSG, many foods naturally contain high levels of free glutamate [7]. For example, a ripe tomato straight from the vine contains free glutamate levels similar to Worcester sauce [3,8]. Free IMP and GMP also occur naturally in many foods. Animal products like pork, chicken, and tuna are full of IMP, while GMP is most prevalent in mushrooms, yeasts, and plant-based foods [3,9].

Simple food processing techniques like fermentation, curing, and extraction can also increase natural levels of free glutamate, IMP, and GMP by breaking down proteins and genetic material [3,7]. During the production of soy sauce and many cheeses, the fermentation process breaks down soy or milk proteins, respectively, releasing many free glutamate molecules. Similarly, the cooking processes used to produce extracts like Marmite (yeast extract) break down proteins and genetic material to release free glutamate, IMP, and GMP.

This recipe, originally created by Adam Fleischman, capitalizes on the umami flavor of several common natural and processed ingredients to create one insanely tasty burger.

Approximate free glutamate content of Umami Burger ingredients. Approximate content of IMP and/or GMP is also reported for some ingredients. All values are reported as milligrams per 100 grams of the ingredient and are based on those reported in [3,7,8,10,11].

Adam Fleischman’s Umami Burger
Makes 4 burgers

Umami Ketchup
1 32-ounce can San Marzano tomatoes
1 medium onion, chopped
3 tablespoons olive oil
2 tablespoons tomato paste
½ cup packed dark brown sugar
½ cup cider vinegar
1 teaspoon salt

Purée the tomatoes with the juice from can in a blender until smooth. Cook the onion in oil in a heavy saucepan over moderate heat, stirring, until softened, about 8 minutes. Add the puréed tomatoes, tomato paste, brown sugar, vinegar, and salt and simmer, uncovered, stirring occasionally, until very thick, about 1 hour. Purée the ketchup in a blender until smooth. Chill, covered, overnight for flavors to develop.  Then add the umami seasonings to taste and chill the ketchup until needed.

Umami Seasonings
2 salted anchovies, cleaned
Worcestershire sauce
Truffle salt

Combine the anchovies with the remaining ingredients to taste. Blend in a mortar and pestle or, for larger quantities in a blender or food processor. Set aside.

Oven-Dried Tomatoes
1 tablespoon brown sugar
1 tablespoon tomato paste
¾ teaspoon soy sauce powder
½ teaspoon Worcestershire sauce
2 pounds ripe tomatoes, sliced

Preheat the oven to its lowest temperature setting. Stir the brown sugar, tomato paste, soy sauce, and Worcestershire sauce together; brush on the sliced tomatoes. Put the tomatoes on a line sheet pan; dry in the oven overnight.

Caramelized Onions
2 pounds large onions
1 tablespoon unsalted butter
1 tablespoon vegetable oil
½ teaspoon table salt
2 star anise

Cut the onions in half from pole to pole; peel and slice across the grain to ¼-inch thickness. Heat the butter and oil in a 12-inch nonstick skillet over high heat; when the foam subsides, stir in the salt and star anise. Add the onions and stir to coat; cook, stirring occasionally, until the onions begin to soften and release some moisture, about 5 minutes. Reduce the heat to medium and cook, stirring frequently, until the onions are deeply browned and slightly sticky, about 40 minutes longer.

Parmesan Crisps
3 ounces Parmigiano-Reggiano

Preheat the oven to 375°F. Using the largest holes on a box grater, coarsely shred enough cheese to measure 1 cup. Line a large sheet pan with a nonstick liner, like Silpat. Arrange tablespoons of cheese 2 inches apart on the liner. Flatten each mound slightly with a spatula to form a 3-inch round. Bake in the middle of the oven until golden, about 10 minutes. Cool for 10 minutes on sheet on a rack; then carefully transfer each crisp with a metal spatula to a rack to cool completely.

To Assemble and Serve
1 ½ pounds assorted cuts of well-marbled beef (short rib, flap, skirt, brisket or hanger)
Vegetable oil
Salt and freshly ground black pepper
1 tablespoon butter
6 ounces shiitake mushrooms, stems removed
4 soft buns (potato or Portuguese), halved

Grind the beef coarsely in a meat grinder or food processor. Put 6 ounces of meat into a 4-inch ring mold and gently tap down to form into a patty. Heat a cast iron skillet on high for 5 minutes. When it’s very hot, pour in a drop of vegetable oil to lubricate the pan. Season the patties liberally with salt and pepper. Add the patties to the skillet and sear on one side for 3 minutes; flip once and sear for 2 more minutes for medium rare.

In another skillet, add half of the butter and sauté the mushroom caps for until soft, about 2 minutes. Set aside. Remove the beef patties to rest. Wipe the mushroom skillet and toast the buns cut side down with the remaining butter.

Remove the buns when toasted and add spread about 2 tablespoons of the umami ketchup on both halves of the bun. Stack a beef patty with 1 tablespoon of the caramelized onions, a parmesan crisp, 2 mushroom caps and 2 slices of oven dried tomato. Serve immediately.

Additional Resources

  1. Recipe adapted from Star Chefs
  2. “The Myth of MSG with Harold McGee” from Mind of a Chef
  3. Mosby, Ian. “‘That Won-Ton Soup Headache’: The Chinese Restaurant Syndrome, MSG and the Making of American Food, 1968-1980.” Soc Hist Med (2009) 22 (1): 133-151.

References Cited

  1. Ikeda K (2002) New Seasonings. Chemical Senses 27: 847–849. doi:10.1093/chemse/27.9.847.
  2. Nakamura E (2011) One Hundred Years since the Discovery of the “Umami” Taste from Seaweed Broth by Kikunae Ikeda, who Transcended his Time. Chemistry – An Asian Journal 6: 1659–1663. doi:10.1002/asia.201000899.
  3. Yamaguchi S, Ninomiya K (2000) Umami and food palatability. J Nutr 130: 921S–6S.
  4. Li X (2002) Human receptors for sweet and umami taste. Proceedings of the National Academy of Sciences 99: 4692–4696. doi:10.1073/pnas.072090199.
  5. Kurihara K (2009) Glutamate: from discovery as a food flavor to role as a basic taste (umami). Am J Clin Nutr 90: 719S–722S. doi:10.3945/ajcn.2009.27462D.
  6. Zhang F, Klebansky B, Fine RM, Xu H, Pronin A, et al. (2008) Molecular mechanism for the umami taste synergism. Proceedings of the National Academy of Sciences 105: 20930–20934. doi:10.1073/pnas.0810174106.
  7. Ninomiya K (1998) Natural occurrence. Food Reviews International 14: 177–211. doi:10.1080/87559129809541157.
  8. Rundlett KL, Armstrong DW (1994) Evaluation of freeD-glutamate in processed foods. Chirality 6: 277–282. doi:10.1002/chir.530060410.
  9. Maga J (1995) Flavor Potentiators. Food additive toxicology. New York: M. Dekker. pp. 379–412.
  10. Skurray GR, Pucar N (1988) l-glutamic acid content of fresh and processed foods. Food Chemistry 27: 177–180. doi:10.1016/0308-8146(88)90060-X.
  11. Populin T, Moret S, Truant S, Conte L (2007) A survey on the presence of free glutamic acid in foodstuffs, with and without added monosodium glutamate. Food Chemistry 104: 1712–1717. doi:10.1016/j.foodchem.2007.03.034. 

ProfileImageSmallAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

Read more by Liz Roth-Johnson