Tag Archive for: taste

Texture and Color of Sashimi

photo credits (sake puppets/flickr)

Whether or not you like eating sashimi, such a fine specimen of fish is undeniably an incredibly beautiful food. The subtle flavors, delicate texture and vivid colors make sushi and sashimi such a unique eating experience. To whet your appetite for The Science of Sushi at UCLA, here are some bits of sashimi science we learned from Ole G. Mouritsen’s book, Sushi: Food for the Eye, the Body, and the Soul.

Sashim刺身

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Salmon and Tuna Sashimi – Photo Credits: (avlxyz/flickr)

Why are fish muscles soft?

If you used your finger to poke a raw filet of a bony fish like salmon or tuna, then tried this on meat from a terrestrial animal like beef or pork, you would notice that fish muscle is significantly softer than terrestrial meat. On a very fresh piece of fish, you could poke your finger through the muscle. From a basic understanding of meat texture, it seems strange that the meat of a fast-swimming predator is soft while the flesh of a slow-moving grazer is firm; typically the more an animal uses its muscles, the tougher its muscles.

Yet fish tend to have the same density as the water in which they live, so they do not use their muscles to bear their own weight; fish need only to exert their muscles when they want to move. By contrast, terrestrial animals frequently use their muscles to counter gravity and remain upright. Fish simply have less work to do, and so their muscles do not develop the same chewy texture that land animals do. But not all fish have smooth and tender muscles; some species like shark have tougher meat. Why? Sharks’ bodies happen to have a specific gravity greater than the water they inhabit, so they must exert their muscles at all times to keep afloat, and thus their muscles more closely resemble a ruminant’s in firmness.

Fresh is best

About six hours after the fish is killed a phenomenon common to all animals, rigor mortis, sets in. During rigor mortis calcium ions of the proteins embedded in the muscle fibers are released, causing the muscle fibers to contract and become stiff.

To delay rigor mortis for up to a few days, fish can be deep-frozen immediately after they are caught. Once the process of rigor mortis has run its course, the fish begins to decompose, the muscle fibers separate, and the connective tissue loosens. At this point it is ideal to consume the fish, as it is at its peak of softness and freshness. This type of sushi is called nojime, the type made from fish that are not kept alive after being caught. The opposite is ikijime sushi, prepared from fish with firmer muscles as they are kept alive until the last moment and prepared before rigor mortis can set in.

A rainbow of fish

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Orange, pink, red, white; there is remarkable variation in fish meat color. Photo Credit: Kake Pugh (kake/flickr)

Orange and pink

The muscles of wild salmon and sea trout are typically orange-pink in color. The origins of this distinct shade of salmon begins at the bottom of food chain, with plankton. These little organisms contain a pigment astaxanthin. It belongs to the family of pigments called carotenoids, which includes the pigment that makes carrots orange. Tiny crustaceans eat plankton, and thus ingest astaxanthin, whereupon it is bound to proteins called crustacyanins in the animals’ tough shell. While bound to these proteins, the pigment is blue-green or a dark red-brown. This will seem familiar if you have ever seen live crab or lobster. When a fish comes along and eats the crustacean, the crustacyanins are denatured and they release the pigment, allowing its own red-orange color to become visible. The color change that occurs upon cooking crustacean shells is caused by the same protein-denaturation and pigment-release process that occurs in fishes’ digestion systems.

Red Fish

Although the proteins that form the muscles themselves are colorless, a lot of fish meat is deep red, like tuna. These colored muscles are classified as slow muscles, as they take care of work that has to be carried out on an on-going basis, namely, continuous swimming. Since they require a continuous oxygen supply to produce energy, they contain myoglobin. Myoglobin is responsible for the transport of oxygen within muscle tissues. Each myoglobin molecule can bind one oxygen molecule to form oxy-myoglobin, which is bright red.

White fish

In contrast to slow muscles, fast muscles undertake smaller and more rapid movements like the slapping of fins and tail. These muscles do not contain myoglobin; instead they use the colorless starch glycogen to supply energy. No myoglobin means that these muscles stay colorless or white.

Interested in learning more sushi science from the experts? UCLA Science & Food’s public lecture, The Science of Sushi, is on April 23rd. In this lecture, Dr. Ole Mouritsen will illuminate the science underlying sashimi, nori, sushi rice, umami, and more.  He will be joined by Chef Morihiro Onodera who will share his approach to sushi as well as an inside look into his partnership with a rice farm in Uruguay.

References:

  1. Mouritsen, Ole G. Sushi: Food for the Eye, the Body & the Soul. New York: Springer, 2009. Print.

 


Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

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Wasabi

Photo credit: Jun OHWADA (しそ山葵) (june29/Flickr)

Photo credit: Jun OHWADA (しそ山葵) (june29/Flickr)

Wasabi packs quite a punch, but where exactly does that wallop of heat come from? That green dollop that accompanies sushi comes from the wasabi plant, also known as Japanese horseradish, which is not to be confused with its distant cousin, the more common and well-known European horseradish (Armoracia rusticana). As a member of the Cruciferae family, wasabi is actually more closely related to cabbage, cauliflower, broccoli, and mustard [1][2].

Grown primarily in Japan, the wild-type species (Wasabia tenuis) are only found mountainside in streambeds and river sand bars [2]. Cultivated wasabi plants (W. japonica), similar to the wild-type variety, comprise a cluster of long-stemmed heart-shaped leaves and delicate, spring-blooming, white flowers branching from a gnarled, thick, root-like stem known as a rhizome [3]. Wasabi grown under semi-aquatic conditions are called sawa, while those grown in fields are called oka [1][3]. Sawa is considered higher quality, as they produce larger rhizomes, thereby often cultivated for culinary purposes. Oka is largely cultivated for nutraceutical purposes, such as herbal supplements [3].

Wasabi rhizomes. Photo Credit: Jaden (Steamy Kitchen)

Wasabi leaves and rhizomes. Photo credit: Jaden (Steamy Kitchen)

The plants are notoriously difficult to cultivate, as they thrive best in running water [4]. Even under ideal conditions, wasabi is difficult to farm, especially on large-scale operations for commercial purposes. As such, real wasabi is expensive and rare outside of Japan. Due to the taste similarities between wasabi and horseradish, common wasabi substitutes are usually a mixture of horseradish, mustard, starch, and green food coloring. So how does one differentiate between real and imitation wasabi? Simply taste it.

Real wasabi is made by grating the wasabi rhizome into a fine powder. Due to the high volatility of the flavor compounds, after grating the rhizome, the heat will only last for, at most, fifteen minutes, whereas horseradish-based wasabi can be left overnight and still retain its heat [1]. Additionally, though the chemical makeup of horseradish and wasabi may be similar, it is different enough that each has a unique flavor profile. Both horseradish and wasabi rhizomes contain thioglucosides, a sugar glucose with sulfur-containing organic compounds. Maceration of the rhizome, such as by grating, breaks the cell walls and releases these thioglucosides, as well as an enzyme known as myrosinase [1]. Myrosinase is responsible for breaking the thioglucosides into glucose and a complex mixture of a class of compounds called isothiocyanates. Horseradish and wasabi contain varying isothiocyanate amounts and compositions. There are 1.9g total isothiocyanates per kilogram of horseradish, as opposed to 2.1g/kg in wasabi. The most abundant and stable of these compounds, allyl isothiocyanate, gives real and imitation wasabi its infamous pungency [1][4]. The next most abundant isothiocyanate compound is 2-phenylethyl isothiocyanate, which is only found in horseradish [1]. All other types of isothiocyanates exist in higher concentrations in wasabi than horseradish.

AllylIsothiocyanate_Wasabi-03

Allyl isothiocyanate produces a hotness in wasabi that is distinct from the spiciness of hot peppers. Hot peppers contain capsaicin, an oil-based molecule which stimulates the tongue. This spiciness can only be washed away with foods containing oils or fats, such as dairy products. Unlike capsaicin, allyl isothiocyanate vapors stimulate the nasal passages. Fortunately for heat-seekers, the amount of pain is directly related to the amount of wasabi consumed, and a little will go a long way. Fortunately for mild-lovers, because allyl isothiocyanate is not oil-based, the burning can easily be cleansed by consuming more of any food or liquid. Although real wasabi is expensive and only found at specialty stores or prepared to order at high-end restaurants, that sinus-opening sharpness is worth experiencing, even if only once.

References Cited

  1. Arnaud, CH. What’s That Stuff? Wasabi. Chemical & Engineering News. March 2010; 88(12): 48.
  2. Fresh Wasabi and Real Wasabi Paste – Technical Info.” Pacific Farms by Beaverton Foods. Beaverton Foods.
  3. The Story of Wasabia Japonica.” Wasabia Japonica, Oka Wasabi, Semi-aquatic Sawa Wasabi. Pacific Coast Wasabi.
  4. Wasabi (Wasabia Japonica (Miq.) Matsum.).” Gewürzseiten: Wasabi (Wasabia Japonica, Japanischer Meerrettich/Kren, わさび, 山葵).

Alice PhungAbout the author: Alice Phung once had her sights set on an English degree, but eventually switched over to chemistry and hasn’t looked back since.

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Chocolate

Photo credit: Eli Duke (eliduke/Flickr)

Photo credit: Eli Duke (eliduke/Flickr)

There are few things sweeter in life than chocolate, which is probably why it’s one of the most popular flavors in the world. We can thank the cacao trees (Theobroma cacao) for this gift, which are only grown within a region known as the Cocoa Belt, 10° to 20° north and south of the equator [1]. Chocolate is produced from the seeds of the pods that grow from the cacao trees; these seeds are better known as cocoa beans.

Chocolate is a complex flavor, containing over 200 different flavor compounds [3]. While the type and mixture of cocoa beans that go into a chocolate bar play a role in determining the final flavor, chocolate is the kind of food where its taste is influenced by how it’s made rather than what it’s made of [4]. The chocolate-making process varies among types of chocolate (milk, dark, bittersweet, etc.), but also depends on the style of the chocolate maker. So while the general principles and chemical processes at each step remain the same, chocolate-making is a delicious art form.

Straight off the trees, cocoa beans are bitter. When cacao pods are harvested, they are cracked open and left to sit for a couple of days, depending on the tree varietal. (5–6 days for forastero versus 1-3 days for criollo [2].) This allows the cocoa beans to undergo fermentation, a process that is carried out by naturally occurring yeast and bacteria. During fermentation, the microorganisms digest the pulp in the pods, which aids in converting the sugars in cocoa beans into acids. These acids decrease the overall bitterness of the beans. Notable flavor compounds, such as pyrazines, are also generated during fermentation, making the beans slightly more floral in aroma [2]. After fermentation, the beans are scraped from the pods to dry. Drying releases certain molecules from the beans that would otherwise make chocolate taste smoky and sour [2].

Roasted cocoa beans. Photo credit: AnubisAbyss/Flickr

Roasted cocoa beans. Photo credit: AnubisAbyss/Flickr

The dried cocoa beans now taste nutty, bitter, and acidic; to drive out volatile (easily evaporating) acidic molecules, the dried beans are further processed by roasting. The elevated temperatures of roasting (120–150°C) also facilitate Maillard reactions that yield flavor molecules that are distinct to chocolate [2]. These reactions are sensitive to both temperature and pH, so both the roasting temperature and bean acidity contribute to the final composition of flavor molecules that form during these Maillard reactions. Typically, milk and certain dark chocolates are made from beans that have been roasted at lower temperatures [2]. The shells of roasted beans are then removed, leaving behind pieces called cocoa nibs. Depending on the chocolate-maker, cocoa nibs may undergo alkalization, whereby they are treated with an alkaline solution in order to further decrease their acidity. Alkalization also causes flavonoids to polymerize (link together), which reduces the astringency of the nibs [2].

The final phase in chocolate manufacturing is a two-step process known as conching. At this stage, the nibs have a gritty texture; the first step in conching turns this into a paste through grinding and heating. Acidic compounds and water are evaporated in this process. More importantly, many flavor compounds formed during fermentation and roasting that are responsible for astringent and acidic notes become oxidized during conching, which mellows the flavor of the final product [2]. In the second step, cocoa butter and soy lecithin are added, decreasing the viscosity of the chocolate mixture to make it flow more easily.

Cocoa beans go through quite a long journey, from the cacao tree to the candy wrapper, where each step plays a role in producing the final combination of flavor molecules that makes chocolate such a beloved treat. This is just one of many reasons to savor your next taste of chocolate.

References Cited

  1. “Cacaoweb.” About the Cacao Tree and Cacao Varieties. <http://www.cacaoweb.net/cacao-tree.html>.
  2. Afoakwa EO, Paterson A, Fowler M, Ryan A. Flavor Formation and Character in Cocoa and Chocolate: A Critical Review. Critical Reviews in Food Science and Nutrition. October 2008; 48(9): 840-857, DOI: 10.1080/10408390701719272.
  3. Schieberle, P. and Pfnuer, P. Characterization of Key Odorants in Chocolate. Flavor Chemistry: 30 Years of Progress. 1999: 147–153, DOI: 10.1007/978-1-4615-4693-1_13.
  4. Ziegleder G, Biehl B. Analysis of Cocoa Flavour Components and Precursors. Analysis of Nonalcoholic Beverages: Modern Methods of Plant Analysis. 1988; 8: 321-393.

Alice PhungAbout the author: Alice Phung once had her sights set on an English degree, but eventually switched over to chemistry and hasn’t looked back since.

Read more by Alice Phung


Why Do We Bother to Eat Bitter?

Photo credit: Melissa McClellan/Flickr

Mustard Greens (photo credit: Melissa McClellan/Flickr)

Through exploration of the ancestral context of taste, scientists can better understand how modern humans use the sense of taste to make decisions and survive. Evolution has shaped our sense of taste to guide us to seek the food we need to survive, while steering clear of foods harmful to us. It is understandable that early humans who avoided spoiled meat and poisonous berries were able to pass down their genes, giving modern humans the ability to avoid them too. But what explains the countless humans who voluntarily consume, and even enjoy, some bitter foods? Why do we eat bitter greens? Brussels sprouts? Hoppy beers? Why do we tolerate some bitter flavors and not others?

Tastes can be positively or negatively palatable depending upon their context among other food flavors. Sour fruit flavors like grapefruit or cranberry can be refreshing and delicious to eat, but sour milk clearly signals that the food has expired. These matches between tastes and flavors are called flavor congruencies.

Most taste-odor flavor pairings are learned associatively through eating. Flavors associated with calories and nutrients become more pleasurable with time, whereas poisoning and illness teach us to associate foods with an unpleasant taste or disgust. For omnivores like us, learning the consequences of eating different foods is an indispensable survival tool. Because our range of food option is so vast, it is essential to sample many foods and connect their post-ingestive consequences with their perceived tastes. Bitter-tasting substances are innately disliked by infants and children presumably because most bitter compounds are toxic. Most children are drawn to all things sickeningly sweet, but as adults enjoy eating eat bitter Brussels sprouts. We learn to enjoy the taste of mildly bitter foods, especially when paired with positive metabolic and pharmacological outcomes. The more your body benefits from an ingested food, the more palatable it becomes [1].

Our bodies require phytonutrients such as flavonoids that cannot be physically separated from their vegetable carriers. Humans learn to tolerate low levels of bitterness in foods as they co-occur with nutrients in plants through a post-digestive reward/punishment system. For example, rhubarb contains 0.5% oxalic acid by weight, a substance that in large doses can cause joint pain and fatal kidney stones. The first time a child eats rhubarb, the initial taste response tells the brain that the food is bitter, toxic, and should be avoided. However, as the body begins to benefit from the essential nutrients in rhubarb without suffering any damage, the rhubarb becomes more and more palatable. Experiments show that rats can very quickly learn associations between tastes and metabolic and physiological consequences, perhaps in a matter of days. These associations occur after only a single trial and are strong enough to resist fading away even after multiple presentations of the food with no physiological consequences [2].

In humans, a large sugar molecule called maltooligosaccharide (MOS) presents a sweeter case of taste association. Human saliva transforms starch into MOS. Although MOS is tasteless, it activates brain reward centers in a manner similar to sugar, while non-nutritive sweeteners do not. Thus, a tasteless molecule that has positive metabolic outcomes can activate brain reward areas more effectively than a sweet-tasting substance that has little nutritional value [3].

The next time you eat mustard greens, stop to appreciate the complex process that allows you to taste and enjoy your leafy meal. Consider how your perception of taste has evolved, which has protected your ancestors from poisoning themselves. Reflect upon the incredible and complex mechanisms humans have developed to keep you well nourished. And if you still haven’t warmed up to greens, consider introducing them gradually into your diet.  By exploiting the body’s associative adaptation to taste, you could learn to love them.

References Cited

  1. Breslin, P. 2013, An Evolutionary Perspective on Food and Human Taste Current Biology, Vol. 23 Issue 9
  2. Sclafani, A., Azzara AV., Lucas, F. 1997, Flavor preferences conditioned by intragastric polycose in rats: more concentrated polycose is not always more reinforcing, Physiology & Behavior
  3. Chambers ES, Bridge MW, Jones DA., 2009, Carbohydrate sensing in the human mouth: effects on exercise performance and brain activity, The Journal of Physiology

Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

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Soda Consumption & Fat Perception

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Researchers at University of Alaska analyze carbon isotopes to measure soda consumption, while German scientists study how our psychological state affects how we taste and perceive fat.

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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.

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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
Tamari
Worcestershire sauce
Marmite
Truffle salt
Harissa

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