What is very unusual about umami is that the intensity of the taste it imparts is not solely dependent on how much glutamate is present. To a much greater extent, it is affected by synergistic interactions with other substances that increase its gustatory intensity. Most often this involves a 5’-ribonudeotide, especially inosinate and guanylate. Somewhat imprecisely and proverbially, it has been said that the taste imparted by equal amounts of glutamate and a nucleotide is eight times stronger than that produced by glutamate alone. As we will see, however, the synergistic effect can be much stronger.
In the explanation that follows, we will refer to the two aspects of umami as a basal contribution, based on free glutamate, and a strengthening or synergistic contribution, which is due to the presence of 5’-ribonucleotides.
The fantastic synergy between glutamate and nucleotides can best be illustrated by a simple example. The threshold for being able to taste pure glutamate in water is 0.01–0.03 percent weight/volume (w/v). But if a small amount of inosinate, which has no taste, is also present in the water, the threshold falls to 0.0001 percent w/v, about one hundred times less. (See the tables at the back of the book.) Guanylate is more than twice as effective as inosinate. We also know that there can be similar synergistic interactions between different substances that produce a sweet taste, but they are far less powerful than those associated with umami.
Naturally, cooks in all parts of the world have, throughout the ages, had empirical knowledge of this synergistic effect, but it was not quantified or explained scientifically. It is only recently that we seem to have come closer to an understanding of this mechanism. Paradoxically, the synergistic effect makes it much harder to evaluate the taste of pure inosinate, because human saliva normally contains a miniscule amount of glutamate, about 0.00015 percent.
The culinary arts can be said to be a study of how to maximize umami by taking advantage of the gustatory synergy produced by combining different ingredients. In the preparation of a dish, one will typically incorporate some ingredients that contribute glutamate and others with nucleotides. (See the tables at the back of the book.) Examples of this can be found in just about any cuisine anywhere in the world. But there are none that have a single central element that has put the stamp of umami on an entire food culture in the way that dashi has on Japanese cuisine. As explained a little later in this chapter, this was why we chose to take this versatile soup stock from the kitchen to the laboratory, in an effort to unlock more of the secrets of umami.
The Japanese researcher Shizuko Yamaguchi carried out a seminal study based on psychophysical observations, which resulted in an actual formula for the synergy in umami. As shown in the following illustration, the subjective experience of taste intensity increases when glutamate and inosinate are present at the same time. In the experiment, the total concentration of the two substances remains constant (50 mg/100 g), but the proportion of each varies. At this concentration, both pure glutamate and pure inosinate result in very weak taste intensity, but when they are mixed together, the intensity increases and is strongest when there are equal amounts of each. The bell curve derived from these measurements has given rise to the popular saying about synergy in umami: 1 + 1 = 8.
Curve showing the subjective perceptions of the taste intensity of umami produced by a mixture of MSG and IMP, where the proportion of the two components in the mixture varies but the combined amount is constant and lies below the detection threshold of each of the two components. The curve shows that when small quantities of one are added to the other, the taste intensity rises dramatically. Taste intensity is strongest when there are approximately equal amounts of the two components.
Recent brain scans of research subjects who tasted liquids with umami, in the form of both pure MSG and mixtures of MSG and IMP, support these classical psychophysical measurements. The scans show that there is an area of the brain that responds very actively to umami and that this response is not linear. Measurements of the same type indicate that the area of the brain in question also responds to sweet tastes. Interestingly, the scientists think that this area, part of the orbitofrontal cortex, is the seat of a sort of reward system that is activated when there are advantages to be gained by the individual. This correlates well with the hypothesis that sweetness and umami, from the earliest times, signaled foodstuffs that were rich sources of energy and nutrition, respectively.
Brain scan of the orbitofrontal cortex of a research subject who is tasting something sweet (glucose) and substances imparting umami (MSG and IMP separately and in combination). The images show that sweetness and umami are registered in the same area of the brain.
Dashi is mentioned for the first time in Japanese writings from the eighth century in connection with the fish sauce katsuo-irori, an extract of dried bonito (katsuo) boiled in water. Dashi can be loosely translated as ‘cooked extract.’ It is a water extract made up of two ingredients, konbu and katsuobushi, which contribute glutamate and ribonucleotides, respectively. Dashi is the textbook example of umami synergy.
The preparation of dashi starts by placing konbu in cold water. Most recipes stress that the water is then to be warmed up to just under the boiling point, at which time the seaweed is promptly removed. Under no circumstances is the water to boil, because that will result in a more bitter extract. There are, however, indications that having more control over the extraction process will yield a better outcome. Experiments have shown that a temperature of 60–65°C is optimal and that the best results are achieved by allowing the seaweed to steep at this temperature for an hour in a vacuum-sealed bag in a water bath. Some chefs have asserted that higher temperatures break down glutamate, but this is not correct, given that glutamic acid is stable up to at least 150°C.
Freshly shaved flakes of katsuobushi are then added to the extract, which starts to give off a wonderful, aromatic smell of smoked fish. Again, the best result is achieved if the temperature is not too high, preferably 60–70°C. Any foam that forms on the surface is skimmed off, as it imparts a disagreeable and slightly astringent taste of oxidized fats. The stock is strained to remove the fish flakes. If the stock is not to be used immediately, it is cooled to prevent the volatile taste substances from evaporating. The newly made dashi keeps in the refrigerator for a couple of days and in the freezer for up to 3 months.
Water quality can make an enormous difference in the taste of the dashi, just as it does with tea. Hard water is a less effective medium, whereas soft water will extract more of the salts and the result will be a tastier stock. The hardness of water, which varies from place to place, is determined by its content of calcium and magnesium salts. Soft water, preferably with less than 50 milligrams of calcium oxide per liter, is considered the best for making dashi. In those areas where the tap water supply is quite hard, it can be advantageous to use soft, non-sparkling mineral water instead.
Even though the basic recipe for dashi is very simple, it is still possible to vary it in a number of ways to draw out more, or fewer, harmonious umami tastes. This is because the stock is a water extract that is prepared over a relatively short period of time. This differs from the usual approach in Western cuisines, where meat or soup bones, together with vegetables, are typically simmered for hours, yielding a very robust stock. It is often said that if one puts ten cooks to work making Japanese dashi, they will produce ten different types.
AN EXPERIMENT IN UMAMI SYNERGY
All you need to perform this little kitchen experiment is a can of water-packed tuna and a little tomato paste. The tuna contains inosinate and the tomato has glutamate, which together will create synergy, intensifying the taste of umami.
Drain the tuna and taste it. Rinse your mouth with clean water. Then take a little piece of tuna and crush it with a fork. Add a small amount of tomato paste and mix it in thoroughly. Taste the mixture and note the difference.
There are many ways of making dashi using a variety of ingredients, but they are all based on extracting glutamate from seaweed (konbu) to obtain basal umami. The outcome depends on the quality and freshness of the raw ingredients, as well as on the care taken in preparing the stock. Different cooks all have their own ideas about steeping time, water quality, temperature, and the shelf life of the stock. The traditional way of making dashi uses konbu and katsuobushi. Usually two extracts, first dashi (ichiban dashi) and second dashi (niban dashi), are made one after the other, reusing the ingredients. Only a portion of the glutamate in the seaweed is extracted into the dashi; the amount depends on the type of konbu, the hardness of the water, and the method used to make the stock. The recipes that follow also incorporate suggestions about alternative ingredients that you can use if you are not able to find konbu and katsuobushi or wish to make a purely vegetarian stock.
FIRST DASHI
The first extraction is the finest, yielding the clearest, most delicate dashi. Place the seaweed in water, preferably soft, for about half an hour. Then warm the liquid to a temperature of about 60ºC (140ºF) and keep it at that temperature for half an hour. It is easiest to do this using a water bath. Remove the seaweed and heat the liquid to 60–70ºC (140–160ºF), and then add the katsuobushi flakes. When the flakes have sunk to the bottom, skim off any froth that has formed on the surface and quickly strain the liquid through a very fine-mesh sieve to remove the fish flakes. The dashi is now ready for use, for example, in a consommé.
1 L (4 ¼ c) soft water • 10 g (⅓ oz) dried konbu • 25 g (1 oz) katsuobushi
SECOND DASHI
The second extraction reuses the seaweed and katsuobushi. Water is added to it and it is heated to the boiling point and then allowed to simmer for about 10 minutes. Strain the liquid through a fine-mesh sieve to remove the seaweed and katsuobushi. This extract is darker and has a stronger taste than the first one. The higher temperature has drawn out more glutamate, but also bitter substances. For this reason, the second dashi is suitable for heartier soups, such as miso soup.
konbu and katsuobushi from first dashi • ½ L (2⅛ c) water
The katsuobushi in first and second dashi can be replaced by small dried fish such as anchovies or sardines, known as niboshi, which are a more robust and stronger-tasting source of inosinate. The heads and stomachs of the dried niboshi should be removed before use, as they will otherwise impart a bitter taste. Soak konbu and niboshi in cold, soft water for about half an hour. Then heat the solution to the boiling point. Skim off any froth that may form on the surface and pour the solution through a fine-mesh sieve to strain out the solid pieces. Niboshi dashi is a strong-tasting, robust stock, which is most suitable for miso soup.
KONBU DASHI
If you want to avoid using fish in order to prepare a truly vegetarian dashi, you can make an extraction based solely on konbu. This will yield a dashi with glutamate, but because it lacks the inosinate from fish the umami taste will be less intense and complex.
This simple konbu extract is commonly prepared according to either of these two ways. To make a very clear, light stock, simply soak the seaweed in cold water for about a day. Or you can follow the method with a warm-water extraction as for first dashi, but without adding the katsuobushi. The warm water extract is a little darker and has a slightly stronger taste than the one made with cold water.
1 L (4¼ c) soft water • 10 g (⅓ oz) dried konbu
SHŌJIN DASHI
Shōjin dashi is also a vegetarian stock, but it is a true dashi in the sense that it depends on synergy to attain a perfect umami taste. As in all other Japanese dashi, glutamate is obtained from seaweed (konbu), but 5’-ribonucleotides are obtained from guanylate in dried fungi, especially shiitake mushrooms, rather than from inosinate in fish. It is important to use dried mushrooms, as these have a greater concentration of guanylate than fresh ones.
Rinse the mushrooms and soak them in cold water for 5 to 6 hours. To speed up the process, you can shred the mushrooms before soaking them. Strain the resulting extract and reserve it. As for first dashi, soak the seaweed and then warm it to 60ºC (140ºF) for about half an hour. Remove the seaweed and mix in the extract from the mushrooms. The shōjin dashi is now ready for use, for instance, in a consommé with vegetables and tofu.
1 L (4¼ c) soft water • 100 g (3½ oz) dried shiitake mushrooms 1 L (4¼ c) soft water • 10 g (⅓ oz) dried konbu
INSTANT DASHI
If you do not have time to make dashi from scratch, a dry soup powder, e.g., Hon-dashi, consisting of dehydrated dashi containing katsuobushi, often with some MSG added to it, can come to the rescue. Packaged preparations for Japanese consommé or miso soup are generally based on dashi powder. Pure konbu dashi powder is also commercially available.
Once one has realized that it takes two components, namely, glutamate and one or more ribonucleotides, to make a clear dashi with good umami, there is nothing to stop one from improvising with local ingredients. These can be chosen by consulting the tables at the back of the book. And then, armed with knowledge of the synergistic properties of umami, all that remains is to experiment with different combinations and methods of preparation until the desired taste is achieved. It becomes an exciting venture into the realm of molecular gastronomy.
Practitioners of the New Nordic Cuisine have a dogma that all ingredients must be from the region. One can remain faithful to the idea of the traditional Japanese dashi while using local seaweeds, such as sugar kelp, winged kelp, or dulse, as a source of glutamate. The problem, however, is that there is nothing that is truly equivalent to katsuobushi. But it could be replaced by dried Nordic mushrooms, cured pork, or prepared chicken. Even though the Nordic varieties of seaweeds have much less free glutamate than konbu, and even though neither mushrooms, pork, nor chicken have as much guanylate or inosinate as katsuobushi, experimentation has shown that one can make a reasonably tasty dashi by using another alga such as dulse or winged kelp. The finished stock is mild, with a slightly floral taste.
Three types of dashi, from top to bottom: konbu dashi, first dashi, and dashi made with the red alga dulse.
It is, however, possible to go one step further and create another type of dashi, resembling a vegetarian shōjin dashi, using ingredients that are available practically anywhere in the world. It calls for only two things—water in which potatoes have been boiled and dried porcini or button mushrooms. When unpeeled potatoes are boiled in lightly salted water, glutamate is drawn out. Older potatoes, especially those that have started to sprout, yield a stronger extract. The sprouting process causes the potato proteins to break down, thereby releasing more free glutamate.
The quest for umami and our wish to participate in a pioneering experiment to create a truly Nordic dashi took Ole to the very epicenter of the new northern gastronomy movement—Nordic Food Lab, located in a small gray houseboat anchored in a side canal in the old inner harbor area of Copenhagen. This unusual food laboratory was established as an offshoot of the standard-bearer of the New Nordic Cuisine, Restaurant noma, which is located nearby on the main canal in one of the beautiful, renovated old warehouses of the North Atlantic House complex. This center is a cooperative effort among Denmark, Iceland, Greenland, and the Faroe Islands, dedicated to preserving and promoting their culture and arts. So both the laboratory and the restaurant are in a setting that is Nordic to the core.
Nordic Food Lab provides the framework for a culinary research project that is based on the idea of seeking out deliciousness in Nordic ingredients. It functions as a kitchen in which one tries to combine a chef’s intuition and experience with scientific knowledge and methods, using a systematic approach. We had set aside two days to go hunting for a Nordic counterpart to Japanese dashi, a new northern ‘mother stock’ for imparting umami.
A large kitchen with a panoramic view of Copenhagen’s harbor has been installed on the uppermost deck of the houseboat. The large room is filled with light reflecting off the water of the inner harbor, which bustles with the comings and goings of small boats. Even though there are counters, sinks, cooking stations, and a great deal of kitchenware, we should actually refer to this space as a laboratory. In contrast to a normal kitchen, plastic containers, all neatly labeled with descriptions of their contents, are systematically arranged on the work surfaces and stacked in the many refrigerators. This is where research on Nordic food ingredients is carried out. The underlying challenge is to create new dishes, the best of which may end up on the menu at noma. But the laboratory also has more ambitious goals. It wants to inject a breath of fresh air into traditional Nordic cuisine for the benefit of everyone, not just the patrons of an elite restaurant. It hopes to reawaken interest in the special tastes of local products, which are a reflection of the particular climatic and geographical conditions that prevail in these northern areas.
The small kitchen is a hive of activity from morning until night. The working language among the chefs and assistants, who are recruited via an international network, is overwhelmingly English. In fact, the atmosphere is surprisingly like that of a dedicated university research laboratory.
At Nordic Food Lab, one can find chefs who have worked at some of the best and most innovative restaurants in the world, such as The Fat Duck in Great Britain and El Bulli (now closed) in Spain. Others have won major prizes for their culinary skills. They are busily engaged in discussions, making notes and drawings on whiteboards. Those who are less experienced are instructed and mentored by those who are masters. Plans are made and the results of experiments are evaluated on an ongoing basis. Tasting spoons are dipped into the food and noses inhale aromas—technological progress notwithstanding, the most precise measuring instruments in the kitchen are still the human senses of taste and smell. Then there are the incredibly accurate quantitative tools—scales and thermometers and thermostats, which enable the cooks to weigh out fractions of grams and to control with great precision the temperature in pots and water baths.
Experimenting with a Nordic version of dashi at Nordic Food Lab in Copenhagen, Denmark.
A whole series of preparations had been made for this set of experiments, which were aimed at creating a new version of dashi from purely Nordic ingredients. Inspired by the Japanese stock, the chefs had gathered ingredients that they hoped would impart sufficient umami. These included seaweeds from cold northern waters, in particular, Danish sugar kelp, Icelandic dulse, and winged kelp from Greenland. Their contribution would be glutamate. The chefs had also prepared several different types of dried chicken, which had first been cooked, smoked, or salted. The chicken was to be a source of inosinate, which works synergistically with the glutamate to yield more umami taste. Another synergistic umami substance, guanylate, could be extracted from the dried button and porcini mushrooms that were on hand. In addition, there was some air-dried smoked ham from the northern tip of Jutland. It could be used to add more glutamate, if the seaweeds turned out to have insufficient quantities.
It appeared that there would be a vast range of possibilities for making dashi. We could use different types of seaweeds and soak them in water at varying temperatures. The extraction could take place over shorter or longer periods of time. Each extraction could then be combined with cooked, smoked, or salted chicken, and the chicken could be cut up into smaller or larger pieces or granulated. Again, the temperature at which this was to take place and the duration of the cooking period could be adjusted. The question then arose as to whether or not to add the fungi to the dashi with the chicken, and whether the mushrooms should be shredded or chopped up first. And for how long and at what temperature should the mushrooms be in the solution? Finally, we also had the possibility of bringing the air-dried ham into the act. There were so many possible variations that it started to look as if working through all of them systematically would become a very time-consuming project.
We had to pare down the list and place our bets on a narrower range of possibilities. So at this point, the expertise and intuition of the chefs took over. We already knew from experience that extracting glutamate from seaweeds should not take place at too high a temperature. In the case of Japanese dashi, the konbu-water solution is traditionally heated to just below the boiling point in order to prevent the release of unwanted bitter substances. We also knew that the taste of dulse changes if it is steeped at over 60ºC. So we decided to steep all three types of seaweeds at 60ºC for half an hour. This would give us three different extracts as our basic dashi.
A tasting session came next. We quickly eliminated the extract made with sugar kelp. It neither tasted good nor smelled appetizing and, besides, the seaweed had exuded so much slime (actually, polysaccharides) that we could barely get it onto a spoon. Perhaps the blades of kelp that we used were too large or coarse; we had to mull over whether we should try again with some finer, thinner blades or possibly some dried blades that had aged for a while. It turns out that if one ages the sugar kelp for about a year, the taste greatly improves and the result is less slimy.
The dulse extract had a very light color and, in contrast to the extract from sugar kelp, it tasted wonderful. It had delicate floral notes of violets and pansies. Even though the taste was mild, it had an appreciably full mouthfeel. It was unmistakably umami, and there was little doubt that we were onto something that would take us further.
The winged kelp extract had a strong taste of the sea and seaweed. It was pale green and actually tasted rather like a vegetable, something along the lines of cabbage or the stalk of a cauliflower. This might be due to some sulfurous substances that had been drawn out of the seaweed. It was not obvious that it was worth pursuing this option further, but we decided to give it a second chance.
For our next step, we ran two systematic sets of experiments in parallel, using the dulse and the winged kelp stocks. The goal was to enhance umami with the addition of chicken. First we tasted the chicken samples and very quickly decided in flavor of the cooked chicken that had been lightly salted, dried, and toasted. But the sample that was only salted and dried was also a possible candidate. We tested them both in the dulse dashi. The pieces of chicken were shredded finely, and 2, 4, and 6 grams, respectively, were added to 250 grams warm dashi, which was kept at 60ºC. After they had soaked for 10 minutes, the liquid was put through a sieve. The clear stock was placed in carefully labeled containers and lined up on the counter. Keeping track of all the possible permutations was proving to be a challenge.
We then moved on to another set of taste tests, both when the dashi was warm and when it had cooled. More cooks were called in, and they arrived, armed with their tasting spoons, to sample and discuss the merits of the stocks. There was overwhelming agreement that the dulse dashi was still good and that the taste of umami in the one with the uncooked, but salted and dried, chicken was an improvement over the basic version. It would appear that there was synergy between the substances from the seaweed and those from the chicken.
We then moved on to another set of taste tests, both when the dashi was warm and when it had cooled. More cooks were called in, and they arrived, armed with their tasting spoons, to sample and discuss the merits of the stocks. There was overwhelming agreement that the dulse dashi was still good and that the taste of umami in the one with the uncooked, but salted and dried, chicken was an improvement over the basic version. It would appear that there was synergy between the substances from the seaweed and those from the chicken.
Much to our surprise, it turned out that the taste of the extract from the winged kelp had changed completely after the addition of the chicken, to the extent that there was now much more umami. At the same time, there was a delicate balance between it and the original interesting sea and vegetable tastes, which had been substantially dampened by the chicken. This was a totally unexpected result that had great potential.
As the first day’s work to create a Nordic dashi was coming to an end, we decided to concentrate our next round of experimentation on the two leading candidates—one stock made with dulse and the other with winged kelp, both with the addition of 4 grams of uncooked chicken that had been salted and dried.
The next day, we took another step in the direction of complexity. We would add another synergistic element—namely, guanylate from dried fungi—to the two types of dashi. We quickly discovered that an extract with the dried porcini mushrooms did nothing for our taste buds. The fungi imbued the mixture with a very metallic taste, and the extract had a quite dark color. So we turned to the dried button mushrooms, which we grated into a light powder. We decided to use 1 gram of the powder for 250 grams of seaweed-chicken dashi. We let the ingredients steep together for 10 minutes and immediately realized that we were on the right track. We agreed that the mushrooms had added a new layer of complexity, which we had a hard time describing, but most likely it was umami. The tasting spoons went to work once more, and we invited any chefs passing through the laboratory to sample the result. We were beginning to feel that perhaps we had hit upon a usable dashi.
Of course, we could not leave without finding out whether the air-dried ham might also improve the dashi. But here we were disappointed. Its salty and smoky character had nothing to contribute, and it did not enhance umami. Fortunately, the ham was primarily there to be eaten, and it was whisked away to become part of our lunch. Another experiment that went by the wayside was our attempt to strengthen the umami taste of the dried mushrooms by first soaking them and then lightly toasting them in a pan. This was completely unsuccessful.
Our experimentation was almost at an end, but we thought that perhaps we should just try to fine-tune the salt content of our dashi. It is well known that table salt (sodium chloride) and sodium glutamate have a synergistic effect on the sensitivity of the taste buds toward saltiness. The result is that umami intensifies the taste of ordinary salt. We made a seaweed salt by toasting a little dried granulated winged kelp in a pan and then mixing it with a few tiny flakes of sea salt. The toasted seaweed had a slightly salty and bitter taste, with nutty overtones, and the sea salt added the final touch. It was now ready to be mixed into our dashi to bring it up to the desired degree of saltiness in perfect balance with umami.
The result of our attempts to create a Nordic dashi had produced two types of dashi that tasted good and had been made exclusively from Nordic raw materials. Even though we had not completely achieved our goal, we had shown that it could be done. There was ample reason to think that further experimentation would yield even more delicious results with more umami. All we would need to do is take into account the complexity of finding the optimal relationship in the proportion of the ingredients and the absolutely best methods of preparing them, invite the chefs to exercise their intuition and creativity, and apply them all in a systematic, scientific manner.
To increase the glutamate content of a vegetarian dashi, you can squeeze the juice out of whole sun-ripened tomatoes, seeds, pulp, and all. The resulting stock has only a faint taste of tomato but has a fair degree of sweetness due to the high sugar content.
We can come even closer to the taste of traditional Japanese dashi made from seaweeds and katsuobushi. The secret is to use smoked shellfish; we have had good results by using powder made from smoked shrimp heads. When combined with potato water or juice from sun-ripened tomatoes, this powder helps to produce a fantastic dashi with a slightly smoky taste reminiscent of katsuobushi. If only potato water and smoked shrimp heads are used, the stock is made entirely from kitchen waste products. 
Potato water dashi with smoked shrimp heads
Fish, especially those from saltwater, contain free amino acids, for example, glycine, which tastes somewhat sweet, and glutamic acid, which is a source of umami. In addition, a newly caught, very fresh fish has free nucleotides, especially inosinate and adenylate, which are formed when the cells of the fish produce energy by breaking down adenosine triphosphate. The nucleotides reinforce umami but, unfortunately, these delicious taste substances slowly start to dissipate after the fish has died.
A classical Japanese technique called kobujime involves wrapping fresh white fish in seaweed. Before the advent of refrigeration it was used to extend the length of time during which the fish could be kept without spoiling.
While the white fish generally has only about 12 milligrams of glutamate per 100 grams, it does contain inosinate. When a fillet of raw white fish—for example turbot, brill, or flounder—is wrapped in konbu or sea tangle and allowed to cure in the refrigerator for one or two days, glutamate is transferred from the seaweed to the fish, which ends up with more than 300 milligrams of glutamate per 100 grams. The glutamate interacts synergistically with the inosinate to produce a much more pronounced umami taste. This, incidentally, turns the white fish fillet into an ingredient that is eminently suitable for use as sashimi. The seaweed can be reused to make soup.
Shrimps are a good source of 5’-ribonucleotides, in particular inosinate and adenylate, providing for synergistic umami. The heads are usually discarded but can easily be turned into a versatile source of umami. First, the heads of small shrimps, either raw or lightly cooked, are smoked in a smoker. If you do not have access to a smoker, it is still possible to make them in a pot with a closed lid on the stove. Place some small grilling/smoking wood chips (for example, apple wood) in the bottom of the pot, place the shrimp heads in a strainer that fits completely inside the pot, and smoke at low heat for 10–15 minutes. Then put the smoked shrimp heads in a food dehydrator or spread them out on a baking sheet and dry them in the oven at 70ºC (160ºF) until they are fully dry. Grind the dried shrimp heads to a powder with a mortar and pestle or grind in a coffee mill. This powder can be stored in a closed container for months.
Smoked shrimp heads.
½ kg (about 1 lb) mature potatoes, unpeeled
1 L (4¼ c) soft water, spring water if available
4 g (¾ tsp) salt
powder made from smoked shrimp heads
1. Scrub the potatoes thoroughly, add the water and salt, and boil them over low heat until they are tender.
2. Pass through a sieve to remove the solid pieces, and reserve the basic stock. Add the powder made from the smoked shrimp heads to taste.
THE FULL-BODIED VERSION
Cooking 100 g (3½ oz) of dried porcini mushrooms or edible field mushrooms along with the potatoes makes the stock even better. To add more umami, combine equal parts of potato water and tomato juice made by squeezing the insides of ripe tomatoes.
More than forty different chemical substances are now linked to umami, but glutamate is still the one that produces the most intense basal umami taste.
Umami is also ascribed to succinic acid, which is found in both shellfish and sake. The same is true of the amino acid theanine, which is the main ingredient in the taste substances found in tea leaves, where it accounts for half of the free amino acid content. Fermented tea like kombucha will have even more umami taste,. There is also a series of small peptides, which are said to draw out or enhance the umami taste.
It turns out that yet another 5’-ribonucleotide, adenylate or adenosine 5’-monophosphate (AMP), which is derived from a nucleic acid, adenylic acid, also interacts synergistically with umami. Adenylate is found in fish and shellfish, for example, and in particularly large quantities in lobster, shrimps, scallops, and squid.
A few years ago, a group of scientists led by Thomas Hofmann from the University of Münster, Germany, searching for new substances that might impart umami, found a chemical substance called alapyridaine. This substance is not present in the raw ingredients, but it is released as beef is cooked to make a soup stock. It can also be produced artificially in the laboratory by heating a sugar-amino acid mixture. Alapyridaine has a discernible effect on umami and is formed only when the raw ingredients are processed.
Alapyridaine itself has no taste. Quite surprisingly, however, it enhances not only the umami taste, which is due to glutamate, but also strengthens the sweet and salty tastes. On the other hand, it has no effect on bitter and sour substances. So it is actually a substance that can make candy and chocolate taste sweeter without the addition of more sugar. The researchers have found that alapyridaine also interacts synergistically with guanylate, resulting in another potential way to increase umami.
Alapyridaine is one of the first substances to be discovered that can enhance more than one of the five basic tastes. It is likely that many similar substances will be found in due course.
Monosodium glutamate has an effect on how we experience sour, sweet, salty, and bitter tastes, but the relationship is complex. The most dominant one is the way it harmonizes with salt, which so often determines whether the food has much taste at all.
Table salt is NaCl, which means that, like MSG, it contains sodium. When these two substances are dissolved in water, their sodium takes on the form of sodium ions (Na+). Taste tests have been carried out in which the sodium concentration from table salt and MSG together was kept constant in a food, but the relative proportion of each was varied. In all cases, the research subjects reported that decreasing the salt content while increasing that of the MSG made the food taste saltier and improved its palatability; there was, consequently, no reason to add more salt. The experiment demonstrated that the judicious use of MSG makes it possible to decrease the salt content of food without losing even a little of its salty taste. This is good news for people with high blood pressure, a health problem that is on the upswing in a large proportion of the population.
One can draw the conclusion that table salt interacts synergistically with glutamate but does not have the same effect on taste as MSG, even though the latter can have the effect of decreasing the amount of salt needed to make the food palatable. Furthermore, the actual taste threshold for salt is not changed by the presence of MSG.
MSG cannot be used as a replacement for sugar, but it seems to be able to intensify the taste of small amounts of sugar. Consequently, MSG can also moderate sour tastes in such products as sweet pickles, salad dressing, ketchup, tomato juice, and other foods with tomatoes, even though the actual taste threshold for sourness appears to be reduced slightly by the addition of MSG. On the other hand, the taste threshold for sweetness does not seem to change when MSG is also present.
The taste threshold for bitterness is the one on which MSG has the greatest impact. In some instances, it has been found that MSG can lower the taste threshold for detecting bitterness by up to thirty times. Still, MSG can be used to mask a bitter taste, because the intensity of bitter is diminished in the presence of umami.
To find out more about the interplay between salt and umami while at the same time gaining experience in recognizing umami, you can carry out this simple kitchen experiment suggested by Anna and David Kasabian.
Dissolve ¼ tsp table salt in 200 mL (⅘ c) demineralized water and let it come to room temperature. Divide the solution into two equal portions and add a pinch of glutamate to one of them. Taste the water that has the salt-only mixture and note the intensity of the saltiness. Then rinse your mouth thoroughly with clean, room-temperature water, repeat the taste test, and rinse again. Now taste the water with both salt and glutamate in the other container. Note that two things have changed. The salty taste is much stronger, and another taste sensation has put in an appearance. That new taste is umami.
UMAMI CAN TAKE THE EDGE OFF A BITTER TASTE
Another little kitchen experiment suggested by Anna and David Kasabian will show you how you can mask a bitter taste with umami.
Coffee tastes bitter because it contains bitter substances such as caffeine. Let a cup of coffee cool to room temperature and taste it thoroughly, swirling it around in your mouth. Make a note of how bitter it tastes. Add a tiny pinch of glutamate to the coffee and ensure that it dissolves completely. Taste the coffee again and judge for yourself whether it is less or more bitter than it was at the beginning.
As a concrete example, let us examine one way in which umami interacts with bitterness. Liver from both fish and poultry has a bitter taste that can have a lingering and somewhat unpleasant aftertaste. By soaking the liver in water or milk, one can remove some of the bitter taste. But it is still important to retain some of it in order not to erase completely the characteristic taste of the liver. This amounts to a challenge to cooks to find a way for diners to encounter the bitterness in such a way that it is carefully balanced by the other taste impressions. It is possible to soften the liver’s bitter taste by introducing umami—for example, by adding tomatoes or anchovies to the recipe—and in that way attaining a balance between the two. An excellent example of this is the preparation of monkfish liver, which itself has some umami. Monkfish liver au gratin with crabmeat and vegetables (page 58)
Only a few decades ago, monkfish was disdained as a relatively uninteresting bycatch when trawling for groundfish or dredging for scallops. There is little question that its appearance worked against it, as it was considered to be one of the ugliest creatures in the sea. With its huge head and enormous mouth, a peculiar sort of antenna used to lure prey toward it, and clumsy mitten-like dorsal fins, it was unlikely to make an appearance on any dinner table as a grilled whole fish.
Monkfish liver.
In the past few years, though, monkfish has come to be appreciated for its taste, and it is now such a sought-after delicacy that there is no longer any justification for calling it ‘poor man’s lobster.’ The flesh from the tail and the cheeks costs a small fortune at the fish store. But there is yet another delicious part of the fish, namely its liver, which has not made many inroads in Western cuisine. This is puzzling, as monkfish liver is held in high esteem in Japan, and some, who have come to know it elsewhere, call it ‘foie gras from the sea,’ putting it on a par with goose liver.
Monkfish liver certainly deserves to take a place alongside the much more common cod liver, which is already a familiar item in some cuisines. It can be prepared so that it is soft and creamy, with good mouthfeel. It has tastes of the sea, but these are mingled with its fattiness and inherent slightly sweet and partly bitter and nutty tastes. In contrast to liver from poultry, or for that matter from cod, which is brownish, it is pale orange, providing a beautiful color contrast in a dish.
A fatty goose or duck liver can have a fat content of 50–60 percent. The fat, which is overwhelmingly made up of unsaturated fatty acids, is distributed throughout in small droplets, which results in a pleasing, delicate mouthfeel. Monkfish liver has only about half as much fat as goose liver, but it is also primarily made up of unsaturated fatty acids. The liver of a fully grown monkfish can be quite large, weighing as much as half a kilogram. Small livers from younger fish are much finer than the large ones, which have a more bitter taste and a coarser texture. Monkfish liver contains only about one tenth as much iron as goose liver, and it is consequently less characterized by the taste of iron than poultry liver is. But it is rich in umami, which can be enhanced by the way it is prepared.
In Japan, monkfish liver, or ankimo, is a major winter delicacy. According to the classical recipe, cleaning the fresh liver involves placing it in a 3 percent salt brine, to which sake has been added, for about half an hour. Then the large veins are removed. One or more livers, placed in cheesecloth or aluminum foil, are rolled tightly using a bamboo rolling mat to form a thick sausage, which is then steamed for 30–40 minutes. It must be cooled before serving and has the best consistency after being left in the refrigerator for about a day. Ankimo is served with a dressing made from soy sauce, yuzu juice (or ponzu sauce in place of both), dashi, and possibly a bit of sake.
It is best to presoak the liver under refrigeration for 12–30 hours to remove some of its bitter taste. This can be done in a 3 percent salt brine or, even better, in milk, which seems to be more effective. Next, the liver needs to be tidied up by removing the blood vessels.
Serves 4
250 g (½ lb) monkfish liver, presoaked in milk for 12 hours
500 g (about 1 lb) vegetables, as follows:
100 g (3¼ oz) ripe tomatoes
100 g (3¼ oz) porcini mushrooms
100 g (3¼ oz) red bell peppers
100 g (3¼ oz) eggplant
100 g (3¼ oz) celery
1 large clove garlic, puréed
2 shallots
¼ tsp fennel seeds
olive oil
1 Tbsp puréed tomato
1 small chile pepper
150 g (5¼ oz) crabmeat
2 egg yolks
1 small sprig fresh dill, chopped
salt and freshly ground black pepper 8 small pieces grilled bread or brioche salsa verde from basil, sage, parsley, anchovies, capers, and olive oil
baked tomatoes and dried olives, for garnish
1. Finely dice the monkfish liver together with the vegetables, puréed garlic, chile pepper, shallots, fennel seeds, puréed tomato, and chile pepper to make a coarse brunoise. Heat some olive oil in a large skillet over medium heat and cook the mixture, stirring constantly, until it has a uniform consistency.
2. Remove from the heat, allow to cool, and put through a food processor to make a coarse mince. Fold in the crabmeat, egg yolks, and dill. Season well with salt and black pepper.
3. Make a salsa verde from basil, sage, parsley, anchovies, capers, and olive oil according to taste.
4. Spread the liver mixture on grilled toast or pieces of brioche and grill in the oven for a couple of minutes.
5. Serve on a bed of salsa verde and garnish with baked tomatoes and dried olives.
Tip: Count on using a little less than 1 kg (2.2 lb) of crab claws, of which about one-fifth is actual crabmeat.
▶ Monkfish liver au gratin with crabmeat and vegetables.
Food pairing refers to a hypothesis that is popular among some chefs. In contrast to the traditional food pairing hypothesis, the principles underlying the synergy in the umami taste, enhanced by teaming up ingredients with glutamate and 5’-ribonucleotides, respectively, is based on a scientific rationale, involving the functioning of the umami receptor. Pairing umami compounds, therefore, has a physiological basis and seems not to be strongly dependent on tradition and regional food culture.
FOOD PAIRING HYPOTHESIS
According to this hypothesis, certain combinations of ingredients that share common flavor compounds taste better than those with no common compounds. This has led to surprising examples of pairings, for example, chocolate with caviar, which both contain trimethyl-amine; and chocolate with blue cheese, which have at least seventy-three flavor components in common. The hypothesis, which is not founded in any scientific rationale, has recently been investigated by a network analysis of 56,498 recipes covering several cultural regions. The investigation showed that, whereas the hypothesis found some support in Western cuisines, the opposite was true for Asian cuisines. The latter seem to avoid combining ingredients that have compounds in common. Hence, food pairing is probably more a matter of tradition and regional food culture than of physiological origin.
Building on discoveries about the nature of basic tastes and especially what brings out umami and synergizes with it, researchers have tried to mix together pure substances to mimic the taste of a particular food, for example, shellfish. Opinions vary as to whether or not this has been successful or if it can even be done. After all, there are still researchers who think that it is not feasible to evoke all other possible taste sensations with only the five basic tastes.
Experiments have been carried out to try to reproduce the taste of scallops. Tasters found that, in a synthetic mixture of glutamate, adenylate, glycine, aniline, and arginine, all the components played a part in simulating the taste of scallops with regard to the five basic tastes, as well as their aftertaste and palatability. On the other hand, inosinate had no effect on such a mixture, which makes sense seeing as scallops themselves have none. (See the tables at the back of the book.)
The food industry is very interested in finding as-yet-unknown natural substances or new synthetic substances that can not only improve the nutritional value and potential health benefits of a foodstuff but also impart a more interesting and appetizing taste. Artificial sweeteners are a case in point, as they produce a sweet taste without adding any calories. This is equally true for substances that result in an umami taste or interact synergistically to enhance it. Different chemical modifications of the known 5’-ribonucleotides have been shown to increase the synergistic effect by up to thirty times as much as the effect produced by guanylate.
Molecular investigations of taste receptors are, to a great extent, driven by commercial interests in systematically developing new taste enhancers and food additives. The degree to which many of the already discovered substances can actually activate the umami receptors continues, however, to be a subject of controversy.
▶ Hard cheeses being aged the traditional way, an excellent example of how to make the most of umami.
A representative selection of raw ingredients and processed food products that contain umami taste substances, ranging from very small quantities (on the left) to an abundance (on the right). The products on the top have basal umami (from glutamate, MSG), while those on the bottom have synergistic umami (from the nucleotides IMP, GMP, and AMP).
Note that the horizontal axes are not linear and the position of a given product on the axis does not correspond to its absolute content of umami substances. Instead, the individual products on each axis are placed in the correct relationship to each other. (See also the tables at the back of the book.)
Basal umami. Glutamate.
1: cow’s milk - 2: apple - 3: carrots - 4: egg
5: pork - 6: Worcestershire sauce - 7: mackerel
8: chicken - 9: green asparagus - 10: caviar
11: green peas - 12: oysters - 13: potatoes
14: ketchup - 15: air-dried ham - 16: miso paste
17: sun-dried tomatoes - 18: walnuts 19: soy sauce
20: dried shiitake mushrooms - 21: anchovies in brine
22: blue cheese - 23: Parmesan cheese - 24: fish sauce
25: Marmite - 26: dried seaweeds (konbu).
Synergistic umami. Nucleotides (IMP+GMP+AMP).
Synergistic umami
1: green asparagus - 2: oyster mushrooms
3: sun-ripened tomatoes - 4: crab - 5: beef
6: lobster - 7: dried shiitake mushrooms
8: scallop - 9: shrimp - 10: pork - 11: chicken
12: mackerel - 13: anchovy paste - 14: katsuobushi
Had we nothing sweeter than carrots or milk, our idea of the quality ‘sweet’ would be just as indistinct as is the case with this peculiar quality [umami]. Just as honey and sugar gave us so clear a notion of what sweet is, the salts of glutamic acid are destined to give us an equally definite idea of this peculiar taste quality.
もし人参あるいは牛乳より甘いものがないならば「甘い」という味の観念はこの独特の（うまみ）という観念の場合と同様に、明確に知ることができないであろう。蜂蜜や砂糖が甘味とは何であるかを教えてくれるようにグルタミン酸塩はその独特の呈味性(うま味)についてはっきりした認識を与えてくれる。
Kikunae Ikeda (1864–1936)
