The Science of Flavor, Part II: Umami, the Taste of Life Itself

Despite the near global recognition of the scientific name of the most recognized molecule responsible for the umami experience, monosodium glutamate--and its ubiquitously recognized and shunned acronym MSG --not many people truly understand what this taste is, where it comes from, and why it has remained controversial over the past many decades.

The sensation of umami was first described (and also named) by Japanese food scientist Kikunae Ikeda in the early 1900s.  Ikeda also founded the company to start the manufacturing of this molecule, extracted from the Kombu sea vegetable (most likely the variant Saccharina japonica var. ochotensis). As a result, the study of Umami that subsequently followed in the decades to come was also predominantly in Japan. The use of umami-rich ingredients in foods is specifically concentrated in Japanese cooking, as was the extraction and popularization of MSG in cooking.  Ikeda was excited about his discovery because he thought to make otherwise bland (healthy) foods taste delicious, and by adding the isolated MSG to foods, would improve the national diet of Japan, encouraging children to eat otherwise less-than-tasty foods (and adults, likewise, though Ikeda viewed this as a less acute problem).

Despite all of the copious linkages between Japan and the umami experience, the negative reputation of this controversial molecule is actually rooted in racism in America against the Chinese, and the reactions to the molecule to this day are still based in what was once termed "Chinese Restaurant Syndrome." The racism is still continuing to this day, pervasive even in conversation I have personally had in just the last week. Despite incontrovertible evidence that there is no traceable toxicity of this particular molecule. Celebrity chef David Chang has pushed back hard against this nonsense.

 “In the public imagination though, it looms largest as an additive to Americanized Chinese food. Chang has been making the point that racism largely underlines the MSG stigma as long as he’s been a famous chef, including in a 2012 talk at the MAD Symposium, a yearly conference for chefs and other food-industry insiders, as well as on his podcast and his Netflix show, Ugly Delicious. “Chang often points to Doritos to highlight cultural assumptions about MSG, and about Asian food being somehow foreign and suspect. He’s right; very few people complain about getting headaches or heart palpitations from eating Doritos, or from dousing pizza in Hidden Valley Ranch dressing.” (1)

MSG is an additive currently used a lot in cheap cooking, and certainly not just Chinese food. It is safe to add to foods, and was envisioned by the scientists who discovered it, Dr. Ikeda, as a solution to make otherwise bland foods taste delicious, thus improving the national diet of Japan.  MSG can be purchased as Aji-No-Moto in Asian grocery stores, usually right next to the salts.  Doritos, and most fried 7-11 style snack foods include MSG in their exhaustively long ingredient list.  As intimated in the quote above, It is the predominant addictive “taste” in Hidden Valley Ranch.  It is nearly ubiquitous among processed foods, and is often added to kimchi and other fresh food items as flavor enhancers.  The reason for the addition of this particular molecule is the desire it creates when we are in its presence.  Umami is so desirable, that MSG is often referred to euphemistically as “legal crack.” Eating a whole bag of Doritos is not exactly a difficult task, though no one says they feel great after doing so.

But why? Why is Umami so desirable and why is our tongue so designed as to alert us to the presence of this particular molecule?  As usual, the answer is to be found in the chemistry.

Amino Acids--understood to be the primary ingredients of umami--are special molecules needed for protein synthesis to build other protein related molecules in the body.  All animals and plants use a combination of 20 different amino acids to construct their DNA and RNA, which is then used to code for the production of various proteins, enzymes and complex chemistry of organic chemistry and biochem. These 20 pieces are essentially the palette of basic lego blocks from which our DNA and RNA draws from to paint the incredibly complex forms that make our bodies function. Essential Amino Acids are amino acids needed for protein synthesis in our body, but are not produced within the body, and therefore must be acquired from external sources, namely, food. Adults humans can produce 11 of the 20 amino acids, but we must get the other 9 from our diets.  That being said, it is unclear if the amount of these “non-essential” aminos produced in the body are actually enough to sustain the body, or if they are only non-essential for a short time).

In addition, all DNA is made up of long chains of 4 nucleotides: adenine, thymine, guanine, and cytosine.  The combination of these four DNA nucleotides, A, T, G and C, read from the DNA in nucleotide triplets (RNA replaces the T with a U--urici--with relatively the same function, though it is produced more efficiently) is what maps combinations from these 20 aminos to form the complex proteins coded for in the genes of all the DNA on earth. Perhaps not coincidentally, the nucleotides that make up the DNA and RNA are manufactured by the body from the amino acids glycine, glutamine and aspartate, the latter two of which are the free aminos that make up the Umami flavors in combination with these same free nucleotides.

The taste of umami is now understood to consist of some combination of the two free amino molecules--glutamic acid and aspartic acid--in combination with free 5’-nucleotides. Yes this seems complicated, but the true experience of Umami is the synergistic effects of the combination of the two; either part of the equation by themselves produce some umami taste, but together they amplify the experience greatly.  The 5’-nucleotides needs for synergy can be:  5’-inosine monophosphate (5’-IMP), 5’-guanosine monophosphate (5’-GMP), 5’-xanthosine monophosphate (5’-XMP), or 5’-adenoshine monophosphate (5’-AMP).  While free aminos are broken bits of proteins, which are made from long strands of aminos linked together,  5’-nucleotides are broken bits of DNA and RNA, or chemically synthesized backbones of the same molecules. Three of these nucleotides in a row in the DNA or RNA strand code for a specific amino acid, and it is these sets of three that determine the proteins our DNA manufactures from free aminos.

Since aminos are needed to quite literally build functional molecules in our bodies, and nucleotides are needed to code these aminos into this complex soup, perhaps it is no wonder that the most exciting and desirable taste is the presence of these molecules in combination in food.  We may be literally tasting the chemistry of our food and reacting to potential protein and genetic building-block content. A pleasing, savory taste, indeed.

In one lab experiment that shows just how tuned in tongues are to the bodies’ needs, researchers removed one single essential amino acid from the diets of several dogs(1).  They then provided a series or four different but identical bowls of food, only one of which was supplemented with the amino acid that had been denied them. 100% of the dogs went immediately to the food with the missing nutrient, suggesting that our tongue is even more tuned in to our nutritional needs than we even know. Cats tongues do not have taste buds sensitive to sugars, but to aminos. (3)

Similar to the desirability of sugar and the resulting obesity, perhaps misusing MSG and other products containing these free nucleotides and aminos might also be to blame for the crisis of obesity. We know that excess sugar is the direct culprit for any number of terribly ravaging diseases for the human body.  Most processed foods these days are nothing more than a combination of MSG, sugar, fat and other chemicals, hardly what the delicate sensors on the tongue were designed to detect, without the underlying promises.

That is, the sweet taste promised to be 1) rare and 2) an important store of energy for the coming winter--such as bears gorging on huckleberries before hibernating. The umami taste promises a protein rich diet full of nutrients such as potassium, phosphorus, and nitrogen, as well as essential amino acids, and protein in general.  But those promises have been broken by the modern food industry, capitalizing on our evolutionary knowledge without delivering the underlying goods.  We are drawn to sweet and savory for evolutionary survival, but with nothing but fat and chemicals under the hood in cheap foods, we are robbed of the true evolutionary satisfaction that both tastes promise, and the result is overeating, obesity, and disease. Through this lens, it is no wonder MSG is viewed suspiciously.

Measuring Umami

Flavor Scientists have created an equation to measure the synergistic effects that these compounds have in food to predict from chemistry the Umami-like flavor intensity.  EUC, or Equivalent Umami Concentration, is the observed experience of umami taste by human tasters, and through chemistry can be predicted by the above equation, with trained human tasters correlating nearly perfectly with the assumed results.

The EUC number that is delivered by the equation relates the experience of umami in a food ingredient to the experience of pure MSG in the mouth. The number ranges from 0.01 to about 2.0. The rating of 1.38 EUC for Agaricus blazeii for example, means that 1 gram of agaricus blazeii, the experience would be equivalent of 1.38 grams of MSG. That is one of the highest EUC ratings in mushrooms, followed by the more common Agaricus bisporus (button, cremini, and portobello). Boletus edulis, for example, have an EUC rating of about .14, a tenth of A. blazei.  As one who loves porcini, I am sure that the volatile chemicals, aroma and even the tastes, play a greater role than the EUC rating in this case, but only the science will tell.

It is also important to understand that as with all chemistry it is not simply the case of whether something contains these compounds or does not contain these compounds.  Guanylate, for example, one of the free 5’nucleotides discussed above (GMP) is found in dried shiitakes, but not fresh shiitakes.  In addition, the process of drying the shiitake mushroom ramps up its glutamate contents by exponential degrees, due to enzyme reactions during the drying process. Even more important to unlocking these flavors in the cooking process, Guanylate can be enhanced by proper handling: the enzyme nuclease, which starts to increase guanylate at 50℃(122℉), and peaks at 60-70℃(140-158℉).  This but one example of why molecule-specific information is useful to cooking accuracy, and why exploring the chemical makeup of various mushrooms will help inform us on how to better prepare, highlight, preserve and extract mushroom flavors.

Maximizing Flavor

How we process our foods has a direct effect on the experience and taste of umami (and other flavors) in our mouths.  Heat and time are important factors, as well as the solvents used.  A solvent is a chemical term for a liquid that allows various chemicals to go into solution. Most people don’t think about water as a “solvent” in cooking, but in chemistry, it is one of the most readily available and incredible of such compounds, drawing from the various meats and vegetables nutrients, vitamins, and flavors!  The most obvious use of this chemical process, for example, is in the making of tea or broth.  We do not eat the solid materials in such recipes, because the water has drawn out everything nutritious and flavorful. Other edible solvents are fats and alcohol, as well as glycerine.

When extracting medicines from many tougher, medically significant fungi, the double extraction method of alcohol (95%; 1-6 months), followed by water (simmering or boiling; 1-2 hours) is used. The resulting solution combines the two in equal volumes, roughly 50% alcohol by volume.  This is a foolproof way to make delicious candy cap extract.  Fats can be solvents of the flavorful fat-soluble compounds and certain colors. Truffle oil is a fine example of this.  I personally had noticed this last fall that the skin of fresh lobster mushrooms from the Cascade Mountains in Oregon turned fats a beautiful saffron-yellow during cooking. I have found nothing about extracting color from mushrooms in cooking, though perhaps the world of mushroom dyers can contribute to this knowledge. (There is clearly more to explore here, and I will dedicate an essay to edible mushroom colors soon!)

It was the aqueous (water) extraction of MSG from Kombu that first attracted the attention of Dr. Ikeda that the Japanese had naturally been using as the basis for their cooking. The study of umami in mushrooms is probably the most molecule-specific research that has been collected regarding the science of cooking mushrooms.

The story of MSG is one of the unfortunate ironies of our modern food industry: patented as a means to better the national diet of Japan, intended to be used to make otherwise less-than-exciting foods more palatable.  And what could be less exciting than food manufactured in labs and filled with processed carbohydrates and manipulated fats? If only the trend had been to put MSG on broccoli instead, Dr. Ikeda. Perhaps we would be living in the healthier world that you envisioned.

Citations:
2) Hou, Y., Yin, Y., & Wu, G. (2015). Dietary essentiality of “nutritionally non-essential amino acids” for animals and humans. Experimental Biology and Medicine, 240(8), 997–1007. doi:10.1177/1535370215587913
3) Hall, J. A., Vondran, J. C., Vanchina, M. A., & Jewell, D. E. (2018). When fed foods with similar palatability, healthy adult dogs and cats choose different macronutrient compositions. The Journal of Experimental Biology, 221(14), jeb173450. doi:10.1242/jeb.173450