Umami - Taste Receptor, Tactile Sensation and Flavor Intensifier

By Matthew Citriglia, MS on October 9, 2006

Does anything stay the same? I just found out that that Pluto is not a planet and that female Reindeer have antlers. And now this- Throughout history we have thought that human beings have only four taste receptors, that we can perceive only the tastes of Salty, Sweet, Bitter and Sour. As it turns out there is a fifth taste receptor called Umami. Umami is the beginning of a whole new sensual pleasure. It is a multidimensional taste sensation that is not only savory, brothy and mouth filling but actually interacts with the other taste receptors. It is a powerful taste that we have known since we were a baby, yet its mysterious interaction with other taste receptors make it hard to describe.

The sense of taste is something we all take for granted as we use it everyday. It seemed like a pretty simple subject when taught to us in biology class. Most of us remember the picture of a tongue with specifically designated taste areas. The tip of our tongue detected sweetness, the side's perceived tartness (acid), salty in the center while bitterness was detected on the back. It seems so easy, why complicate it? Well if you eat and drink merely for nourishment than there probably is no need to complicate or change your perception of taste. But if you have a passion for food and wine like I do, then you need to accept that the simple world of taste is really quite complicated.

Science on the sense of taste has been slow to develop, but we now know our tongue is made up of many taste buds and each taste bud has numerous papillae or taste receptors. A taste receptor can only be stimulated by one type of taste, so some receptors detect sugar while others detect bitter, acid or salt. Since each taste bud has multiple receptors on it, the diagram we were taught in school needs to be rendered obsolete. The other thing science has revealed is that there are papillae that don't respond to the 4 basic taste groups but to other taste stimuli. Two of these unknown papillae are believed to be stimulated by the taste of fat and the taste of capsaicin, or heat from chili peppers. A third unknown receptor has recently been proven to receive the taste called Umami, which at this point we will call savory. Unlike the basic four taste receptors, which I like to call one dimensional tastes, these new receptors taste in 3 dimensions. As we explore the taste of Umami, I think the 3 dimensions phenomenon will be better understood.

To discuss this subject some vocabulary needs to be more strictly defined. Throughout this article taste will refer to chemical agents that dissolve in saliva and stimulate the papillae located on the taste buds. Aroma will refer to any volatized odor that is received into the olfactory bulb behind our nose. This odor can be sensed either through the nose or retro-nasally through the back of the mouth in the form of flavor. When the brain combines the taste stimuli with the aroma stimuli, flavor is perceived. (Tactile sensations such as the astringency from tannin also play a role in flavor.) To fully understand the concepts of aroma, taste and flavor, you may want to review The Flavor of Wine.

History and Discovery

Believe it or not, our first encounter with Umami is as a baby. Baby formulas and mother's milk are loaded with Umami, but it doesn't stop there. Umami can also be detected in many normal every day foods we eat such as ripe tomatoes, parmesan cheese, cured ham, mushrooms, meat, fish, wine and beer. So if we encounter Umami every day why is it so elusive to define? One reason is that we can not buy it in bulk like sugar or salt. (For those who think MSG is Umami, read on, you're only partially correct). Also, it has a strange name; the taste itself is rather subtle; and it actually interacts with the four other tastes.

The name Umami was given by a Japanese scientist that identified the taste sensation. His name was Dr. Kikunae Ikeda and he intended for it to be a temporary name, but it stuck. The word is pronounced oo-MA-mee and is made up of two distinct words:
Umai which means Delicious
Mi which means Essence
Once you understand this gustatory taste response you will agree that foods high in Umami have a delicious essence.

History shows that Umami was around long before Dr. Ikeda discovered the taste in 1907. The Greeks and Romans used a condiment called garum or liquamen, which was a type of fermented fish stock that was added to virtually all dishes of that time. Although the Greeks and Romans knew that this stock made food taste better, they never identified it as a specific taste. They just enjoyed consuming it. Science has proven that modern day fermented fish sauces, such as Worcestershire, are loaded with Umami stimulants.

Centuries later, a type of Japanese fish soup made of Kombu (a type of edible kelp) and Bonito (skipjack tuna) flakes lead Dr. Kikunae Ikeda into the science lab to isolate and identify the substance he tasted but could not describe. His research led him to a type of amino acid called glutamate and from here he created the seasoning known as monosodium glutamate (MSG). This seasoning was an over night success throughout Asia. The instant success of MSG ended Dr. Ikeda's curiosity, but there was still more to discover about the complicated taste of Umami. Also, MSG was viewed by western cultures as a spice that was only to be used in Japanese or Chinese cooking. Later on, MSG became the center of scrutiny for a variety of ailments such as dizziness or the onset of migraine headaches that scared people away from the product. Hence the term Umami never became a household name, and it would still take another 90 years before this taste would be accepted and explored here in the West. In January of 2000, western scientists discovered and isolated the actual taste receptor on the tongue that accepted and reacted to the amino acid molecule known as glutamate.

Taste a Primal Survival Instinct

Listening to Doug Frost MS/MW at a recent seminar, he referred to the trigeminal nerve that runs across the center of our face. This nerve does many things but historically it works in conjunction with our sense of smell and taste receptors sending signals to the brain to determine if something was dangerous or safe to ingest for nourishment. It is essential to our survival. Just watch a baby feed for the first time and you can see the nerve in action as the youngster scrunches its face to refuse the foreign substance you are trying to put in its mouth. The nerve sends a signal to the brain, which in turn says it does not know what the substance is and sends a signal back to the mouth and nose to reject the food.

Now think of our primal ancestors who could not just run down to the store and pick up a loaf of bread and peanut butter. The brain of the starving primate would signal the sugar taste receptors in the mouth that it needed carbohydrates to fuel the body for those long hunts and periods without food. Salt is essential for life as it helps balance electrolytes, prevent hyperthermia and regulate fluids and nutrients in our cells. Foods that were excessively sour or bitter were signs of danger as they are found in many poisons and rancid food. These all make for powerful life threatening circumstances that have brought these taste sensations to the forefront.

Umami on the other hand is the taste of amino acids, which is also very important to human life. Not only do our bodies produce it naturally but it is also found prolifically throughout nature, beginning with mother's milk. Because it is so abundant we don't risk shortages so it doesn't pose the same life and death threat. Hence centuries of conditioning have made us most sensitive to bitter, sweet, sour, and salt even though Umami exists in many of the foods we eat and is essential to life.

Defining Umami

First, let me re-clarify that Umami is not MSG. Although MSG was the creation of Dr. Ikeda as a type of seasoning like salt or sugar it is not the isolated taste of Umami. Umami is the taste of free amino acids which come in many forms; glutamate just happens to be the most plentiful in nature. All amino acids whether essential, non-essential or non-protein have an Umami taste. But whether or not we can detect the taste is determined on if they are free or bonded. The term free means in a state ready for our bodies to use. Free amino acids are instantaneously absorbed by the body and are very restorative (think chicken soup). They do not need to be broken down and extracted through digestion but rather can be absorbed or tasted by the tongue. Many amino acids are bound to a protein, so to taste them they must be freed. Amino acids can be freed from their protein bond by either cooking or by some other type of enzymatic action such as fermenting or curing.

Had Dr. Ikeda continued to investigate Umami he would have discovered that amino acids, such as glutamate, are only one part of a two-part taste sensation. Here is where things get a bit geeky and confusing. The Umami taste receptor contains two parts, a trigger known as amino acids, and an intensifier known as nucleotides (DNA and RNA). The trigger stimulates specific papillae on the taste buds, while the intensifier intensifies the taste of Umami. MSG only contains the trigger, which is why tasting it alone is not a good indicator of the Umami taste. The other unique aspect of this two-part taste is that when they are both activated they also interact with the other four taste sensations. Umami intensifies the taste of salt and sweet, and balances bitter and sour. This interaction draws our attention away from the Umami taste allowing the more well know tastes to take center stage. The aspect that is hardest to describe about Umami is the tactile sensation that is involved with the taste. Mouth filling, meaty, rich and supple are terms commonly used by people experiencing Umami.

So to define Umami as a single taste stimulated by a single factor, like sweet or salty, is incorrect and difficult to do. Umami is a taste that is stimulated by amino acids and nucleotides. It is a savory, mouth filling, brothy, flavor intensifier that you experience regularly but may have never identified. This is why I think of it as a three dimensional taste.

Umami Taste Experiment

This palate training experiment really helped me isolate the Umami Taste and I highly urge any food or wine geek out there to try it. I have done palate training exercises for years in my wine sales and service seminars, but was never able to replicate the Umami sensation. David and Anna Kaspian wrote a book called The Fifth Taste: Cooking with Umami, and in it they have the same type of tasting experiment but include an Umami solution. It is brilliant!

Prepare the following solutions:
• Sweet: 1 cup water with 2 teaspoon sugar
• Salty: 1 cup water with 1 teaspoon salt
• Sour: 1 cup water with ½ teaspoon cream of tarter which is tartaric acid
• Bitter: ½ teaspoon unsweetened baking chocolate - do not mix with water rather chew and coat the mouth with it
• Umami: 1 cup water with 1 tablespoon dried shiitake mushrooms – boil it and then let it cool

By tasting each solution individually you will be able to isolate each individual taste. Make sure you rinse your mouth thoroughly with plain water before tasting each new solution. Taste each solution multiple times to make sure your taste receptors understand their differences. Then taste each solution again but add a small amount of the Umami solution to it. Pay close attention and you will find that the salt and sweet solution become more intense while the sour and bitter sensation are muted or rounded. Remember only add a small amount of the Umami solution, too much will distort the results.

Umami Rich Alcoholic Beverages

Any food that undergoes fermentation or curing for preservation such as pickles or prosciutto has elevated levels of Umami. The same thing holds true for fermented beverages. During the fermentation process, proteins are broken down into simple amino acids. As long as theses acids are unbound they can be perceived by the taste receptors in the mouth. I sampled several beverages to see how Umami taste buds are impacted. Umami is more abundant in old world wines than new world and it seems to intensify as a wine ages. Here are a few examples of beverages rich with Umami:

White Wine
5 year old Sauvignon Blanc from Sancerre or Pouilly-Fumé
10 year old German Riesling from the Rhiengau, Spätlese ripeness or higher
5 year old Smaragd Grüner Veltliner from Austria
10 year old Chardonnay from Burgundy

Red Wine
10 year old Pinot Noir from Burgundy
5 year old Barbera from Piedmont
5 year old Grand Reserva Rioja from Spain
10 year old Côte-Rôtie from the Rhône Valley

Fortified Wine
20 year Tawny Port
Amontillado or Oloroso Sherries
15 year Sercial or Malmsey Madeira

Misc. Beverages
All Sakes
Dark Ales rich with hops
Well-aged Brandies or Whiskey

Umami Rich Foods

The best source for Umami based foods and recipes is also the book The Fifth Taste: Cooking with Umami by David and Anna Kasbian. I researched many books and websites and this book was by far the most detailed and complete. For quick reference the foods are separated into two categories: Umami Triggers and Umami Intensifier.

Umami Triggers
Vegetables: Kombu, corn, peas, tomatoes, winter squash (Umami most noticeable when raw).
Proteins: Dry aged beef, braised or slow cooked proteins, turkey, most seafood, shellfish and all stocks made from these foods.
Cheeses: Aged hard cheeses such as parmesan and blue veined cheeses such as Gorgonzola.
Miscellaneous: Soy sauce, catsup, Worcestershire, miso and dark mushrooms.

Umami Intensifiers

Vegetables: Asparagus, spinach, kidney beans (Umami most noticeable when cooked).
Protiens: Kidneys, liver, veal, venison and cured meats like prosciutto.
Miscellaneous: Pickles, olives, pickled ginger and sauerkraut.

This is only the beginning of new tastes to be explored. Scientists have only recently discovered the fat taste receptor in rats and believe that we have taste receptors for capsaicin as well. It's only a matter of time before scientists discover what I already know to be true: I salivate at the idea of eating foods rich with fat or chili peppers. The more you know about these tastes the more you can explore and exploit them for your own enjoyment.