The MSG Files, Part III: Umami

Our sweet and umami receptors are 50% alike, sharing the T1R3 (aka TAS1R3) receptor. The combination of T1R1 and T1R3 detects umami, while T1R2 and T1R3 perceives sweetness.

Hey, hi, hello! You’ve arrived at Part III of Ink Chromatography’s The MSG Files, a series devoted to untangling all of the controversy surrounding the food additive MSG. If this is your first post, you might want to catch up with Parts I and II before reading on. Today, we’ll be talking all about umami, the black sheep of our five basic tastes. Although it is more difficult to define than the other four tastes, umami stays with you. It satiates your taste buds and lingers pleasantly even after you’ve stopped eating, in a way that can eclipse the salty, sweet, sour, or bitter.

In the last post, I introduced three taste receptors that are responsible for our recognition of glutamate – mGlu4, T1R1+3, and mGluR1. This trifecta helps us experience the gustatory delights of umami. While two of these taste receptors — mGluR4 and mGluR1 — exclusively recognize glutamate, the T1R1+3 receptor does not respond to glutamate alone. Instead, the T1R1+3 receptor also responds to ribonucleotides, which are components of RNA, the single-stranded counterpart to DNA.

Shitaro Kodama discovered that ribonucleotides like IMP can also contribute to umami.

The idea that glutamate is not the sole agent of umami was first proposed by Shintaro Kodama, a disciple of Kikunae Ikeda. In 1913, Professor Kodama discovered an umami-causing compound in dried bonito flakes. These dried, fermented, and smoked tuna flakes are another main ingredient in dashi — the broth that Dr. Ikeda initially set out to emulate, and that forms the basis of miso soup. The compound that Kodama identified was a ribonucleotide called inosine monophosphate (IMP).

Akira Kunika realized that ribonucleotides IMP and GMP have a synergistic interaction with glutamate.

Half a century later, in 1957, a man named Akira Kuninaka found another ribonucleotide that imparts the umami taste – guanosine monophosphate, or GMP. Just as his predecessors had done (Ikeda with kombu and Kodama with bonito), Kuninaka found GMP in a food that he regularly encountered — shiitake mushrooms. Dr. Kuninaka also discovered that ribonucleotides like IMP and GMP interact with glutamate to produce a synergistic umami effect. In other words, when glutamate-rich foods are combined with foods that have IMP or GMP, the umami experience is amplified beyond the sum of its individual parts.

Umami synergies are present in popular dishes across cultures. Image from: glutamate. org

This explains why, across cultures, we enjoy certain combinations of foods. These include Japanese dashi broth with kombu and bonito flakes; the Western combination of beef, onions, carrots, and celery; and the popular Chinese mixture of chicken with cabbage and leek. Perhaps the ultimate composite is pizza: think of a pie with tomato sauce, cheese, and any blend of toppings that might include pepperoni, sausage, mushrooms, anchovies, or parmesan cheese — and imagine the lavish, complex flavors that emerge. That, in a nutshell, is the synergistic effect of umami.

Today, IMP and GMP are often combined into one flavor additive called disodium 5′-ribonucleotides, or E635. It is added to foods that contain glutamate, either naturally or through MSG. As IMP and GMP are rather expensive to produce, they are generally used sparingly, and rarely independently of glutamate. You tend to find E635 in many junk foods such as instant noodles, potato chips, crackers, canned sauces, and fast food. As GMP and IMP mostly come from meat or fish, vegetarians should avoid foods containing E635.

E635’s main effect is to intensify the effects of glutamate — a mixture of 98% MSG and 2% E635 yields quadruple the flavor enhancement that MSG would on its own. In fact, one only needs to add a small amount of MSG to achieve optimum taste in one’s food. MSG makes dishes “pop” by enhancing flavors that are already inherent in foods. The rule of thumb is to use 1/2 a teaspoon per pound of meat or, for a vegetable dish, 1/2 a teaspoon for every 4-6 servings. One can also sprinkle 1/4- 1/2 a teaspoon of MSG on rice or noodle dishes, or add a dash to homemade sauces. Adding MSG in amounts above these recommendations does little to enhance food flavor, and excessive addition of MSG can even eventually decrease the palatability of food.

Some of our umami receptors are located in mushroom-like projections, called fungiform papillae, on the margins of our tongue. Image from: UCLA

Aside from the fact that it registers umami substances other than glutamate, the T1R1+3 umami receptor is interesting because half of it is identical to our sweet receptors. The umami-sensitive T1R1+3 cells are mostly found in palate taste receptors at the roof of our mouth, and mushroom-shaped projections, called fungiform pappilae, at the tip and lateral margins of our tongue.

Our sweet receptors, meanwhile, are made of T1R2 and T1R3 proteins. T1R2+3 cells are also found in our palate taste receptors, as well as in structures called circumvallate papillae and foliate papillae near the back of our tongue. T1R3, which makes up 50% of the T1R1+3 umami receptor, can also function as a sweet receptor on its own, though it has reduced sensitivity, particularly to artificial sugar substitutes.

There is logic to how we perceive tastes. We associate sweetness with carbohydrates, and saltiness with the balance of electrolytes in our bodies. The umami taste, meanwhile, indicates the presence of proteins. Given these relationships, it makes sense that we prefer certain tastes over others. Since carbohydrates and protein are essential for the maintenance and development of our bodies, we have a natural predilection for sweet and umami tastes. In fact, breast milk plays to these preferences early on by offering both tastes – sweetness from lactose, and umami from glutamate. Because salt is involved in balancing ions, we find it unappealing in concentrations that are too low or too high. We tend to dislike bitter tastes, which are associated with toxins, as well as sour tastes, which can indicate that food is either unripe, or, to the opposite extreme, spoiled.

This deviled egg spiced with sriracha hot sauce, soy sauce, and seaweed rice seasoning is loaded with umami.

Glutamate is a powerful taste stimulus that can make foods seem especially delicious. While umami may be the most nuanced of the five basic tastes — in the literature, attempts to describe umami have included “savory deliciousness”, “pleasant savory taste”, “meaty”, “beefy”, “oak-mushroom”, and “sweet-salty” — it is perhaps more addicting than its four counterparts. It rounds out and adds dimension to other tastes in our food. Anyone who enjoys a meal of sushi drenched in pickled ginger, wasabi, and soy sauce understands its magic.

Of course today, through food additives, we can experience umami in foods that are not particularly protein-rich or, for that matter, healthy.  Umami is the taste that keeps us going back for just “one more” potato chip, the reason why snacks taste better with dipping sauces, and the explanation for why ramen noodles can hit the spot. These foods have all been graced with MSG, which simulates the umami taste that is naturally present in seaweed, mushrooms, or a block of parmesan cheese. Ultimately, these foods tickle our taste buds because they contain free glutamate. So, the next time you seriously crave some instant noodles, you can also try getting your umami fix with a ripe tomato or a cup of green tea instead.

MSG is a simple and cheap way to make junk foods taste better.

For reference, here are some other commonly used labels for free glutamate additives:

  • Anything with the word “glutamate” (monopotassium glutamate, calcium glutamate, etc.)
  • Yeast extract/ food/ nutrient
  • Anything with the word “hydrolyzed”
  • Calcium or sodium caseinate
  • Autolyzed yeast
  • Textured/ soy/ whey protein
  • E620 – E625
  • Aijonomoto, Ac’cent
And here are some ingredients that often contain free glutamate additives:
  • Bouillon, broth, stock
  • Natural flavors
  • Seasonings, spices
  • Malt extract
  • Citric acid, citrate
  • Pectin, gelatin
  • Protease
  • Anything containing “enzymes” or “enzyme modified”
  • Anything “protein-fortified”, “ultra-pasteurized”, or “fermented”

And thus ends your crash course on umami. Tomorrow, we’ll be prying into Chinese Restaurant Syndrome! What are its symptoms? How can it be explained? How prevalent is it? All that and MORE, in part FOUR.


4 thoughts on “The MSG Files, Part III: Umami

  1. Pingback: The MSG Files, Part IV: Chinese Restaurant Syndrome « Ink Chromatography

  2. Pingback: The MSG Files, Part IV: Chinese Restaurant Syndrome « Ink Chromatography

  3. Pingback: The MSG Files, Part V: Public Relations « Ink Chromatography

  4. Pingback: Following Up: Is MSG Bad For You? | Ink Chromatography

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