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Taste Tripping With Miracle Berries

May 6, 2014/in Science & Food/by Grant Alkin

Miracle Berries (Wikimedia Commons)

Imagine eating a lemon and puckering to incredibly sour…no wait, incredibly sweet citrus syrup. Then you try some tart goat cheese, but to your surprise, it tastes like sugary frosting. An underripe pineapple? Better than candy. Salt and vinegar chips? Dessert!

This fantastical taste-changing sensation is the real-life effect of a West African fruit called Synsepalum dulcificum (Richardella Dulcifica), or the “miracle berry”, which physically alters taste receptors and causes sour foods to taste sweet.

How does this work?

The secret is a protein found in miracle berries called miraculin.

Miraculin Protein (Wikimedia Commons)

When a miracle berry is eaten, its molecules attach to the thousands of taste receptor cells located on taste buds lining the mouth, tongue, throat, and esophagus. Humans have at least five different kinds of taste receptors to detect five basic tastes: sweet, salty, sour, bitter, and umami. (Note that evidence in the last decade suggests that there may be additional taste receptors for lipids [1] – which may explain our natural affinity for fatty foods!) Miraculin, in particular, binds directly to the sweet-sensing taste receptor known as hT1R2-hT1R3.

The earliest scheme of miraculin-hT1R2-hT1R3 binding was based on a pH-dependent conformational change of the sweet receptor-protein complex. In this model, miraculin binds somewhere near the sweet receptor site (so there is no sweet taste at first), but at a lower pH (in sour or acidic environments), the receptor changes its shape so that miraculin can bind directly on the sweet receptor site and elicits a sweet taste [2]. That’s how miraculin causes a lemon, which creates a sour, acidic environment in your mouth, to taste so sweet!

More recent studies have found additional evidence that miraculin actually starts off directly attached to sweet receptor hT1R2-hT1R3 in neutral pH and activates it in the same place in an acidic environment. Experiments have shown that sweet receptors bound with miraculin are most responsive in acidic pH (4.8-6.5), but in general, the more sour environments lead to a greater intensity of sweet taste sensation [2]. In neutral pH (when miraculin is not activating the sweet receptors), miraculin actually has another effect: it blocks other sweeteners such as aspartame, sucrose, and saccharin, and other sweetness-inducing proteins like thaumatic and brazzein, from attaching to the hT1R2-hT1R3 receptor. Basically, miraculin claims the sweet receptor site for itself so that it can reactivate the site, allowing the magical sensations of sweetness to last for up to an hour.

Even if miraculin can manipulate sweet taste receptors to make a lemon taste sweet, shouldn’t a lemon still taste sour? Little is currently known about whether or not miraculin actually inhibits sour taste receptors, but a neuroimaging study in 2006 has suggested that the electrical signals that transmit sour taste information diminish en route to the brain stem, and that only sweet taste signals even reach the brain for processing. In the study, participants were able to still detect both citric acid and sucrose after miraculin treatment, but the sweet taste dominated because 20% of the sourness may be suppressed at the receptor level, and most of it is suppressed in the central nervous system [3].

Miracle berries were historically used by West Africans to improve the taste of fermented bread and sour palm wine, but today’s applications may be life-changing. Miraculin is being studied as a therapy for chemotherapy patients suffering from dysgeusia, which is an unpleasant metallic taste distortion. In a 2012 pilot study, eight chemotherapy patients, who reported that most foods, including water, tasted metallic, bitter, or “spoiled”, were recruited to test the effects of miracle berries. After eating miracle berries for two weeks, patients showed substantial improvement in appetite, nutrition, and response to treatment because the miraculin either masked or eliminated the unpleasant tastes altogether [4]. In the meantime, expect to see an increased production of recombinant miraculin in transgenic fruits, booming commercial demand for miracle berries as low-calorie sweeteners, and some invites to trendy “taste tripping” miracle berry parties.

References

Degrace-Passilly P, Besnard P (2012) CD36 and taste of fat. Curr Opin Clin Nutr Metab Care 15: 107–111.
Koizumi A., et al. (2011) Human sweet taste receptor mediates acid-induced sweetness of miraculin. Proc. Natl. Acad. Sci. U.S.A. 108: 16819–16824.
Yamamoto C, et al. (2006) Cortical representation of taste-modifying action of miracle fruit in humans. Neuroimage 33:1145-1151.
Wilken M, Satiroff B (2012) Pilot study of “miracle fruit” to improve food palatability for patients receiving chemotherapy. Clinical Journal of Oncology Nursing 16:E173-E177.

About the author: Eunice Liu is studying Neuroscience and Linguistics at UCLA. She attributes her love of food science to an obsession with watching bread rise in the oven.

Read more by Eunice Liu

Dana Small

May 1, 2014/in Profiles/by Grant Alkin

Dr. Dana Small is a Professor in Psychiatry at Yale University, a Fellow at the John B. Pierce Laboratory, and visiting Professor at the University of Cologne. Her research focuses on understanding the mechanisms behind flavor preference formation, investigating the role of cognition in chemosensory perception, and determining how the modern food environment impacts brain circuitry. She currently serves on the executive committee for the Association for Chemoreception Sciences and the Society for the Study of Ingestive Behavior.

See Dana Small May 14, 2014 at “How We Taste”

What hooked you on science? On food?: I just loved biology class. It was love at first sight. I became a neuroscientist interested in flavor and food because I wanted to understand neural circuits that regulate appetitive behavior. Neuroimaging had just become available and I wanted to know if what we understood about the neurobiology of appetitive behavior in rodents applied to humans. The rodent work was based on studies where rats pressed a lever to have food pellets dispensed. I guess that means that rat chow got me hooked on food!

The coolest example of science in food?: Jelly beans because they are the perfect food to demonstrate that “taste” is mostly smell.

The food you find most fascinating?: Soufflé.

What scientific concept–food related or otherwise–do you find most fascinating?: Evolution. I am interested in understanding how the environment shapes biology—including the food environment.

Are there any analogies you like to use to explain difficult or counterintuitive food science concepts?

If I can speak of neuroscience of flavor, then I like to compare the oral capture illusion (which occurs when volatiles that are in the nose are referred to the mouth) with the visual capture that occurs when one watches TV. The sounds comes from the speakers but appears to come from the actors’ mouths.

How does your scientific knowledge or training impact the way you cook?: My scientific knowledge totally influences how I cook and eat. I avoid all artificial sweeteners and liquid calories (OK, except wine). I rarely eat processed food. I buy organic and try to eat locally. I eat a big breakfast and a light dinner. I avoid foods high in glycemic index (except on a special occasion) and search out high fat yogurt as a favorite lunch.

One kitchen tool you could not live without?: In truth I should be kept out of the kitchen!

Four things most likely to be found in your fridge?: Raspberries, blueberries, strawberries, blackberries.

Your all-time favorite ingredient?: Eggplant.

Your standard breakfast?: Steel cut oats, pomegranate seeds, blueberries, raspberries, and sliced almonds. Its my biggest meal of the day. Double latte.

Science of Sushi & Sushi in Space

April 10, 2014/in What We're Reading/by Grant Alkin

Dr. Ole G. Mouritsen discusses his book Sushi: Food for the Eye, the Body, and the Soul, and astronaut Soichi Noguchi prepares sushi aboard the ISS. Read more

Morihiro Onodera

April 8, 2014/in Profiles/by Grant Alkin

Chef Morihiro Onodera trained as a sushi chef in Tokyo, and at seminal Los Angeles restaurants including Katsu, R-23, Matsuhisa, and Takao as well as Hatsuhana in NY. By the time he opened his first restaurant, Mori Sushi in Los Angeles, he was preparing many of the same handmade ingredients, harvesting his own locally grown rice and creating handmade pottery to be used in the restaurant. After selling Mori Sushi in 2011, Mori began creating handmade pottery for several Michelin Guide restaurants in Los Angeles and established a partnership with rice farmer, Ichiro Tamaki. Tamaki farms in Uruguay will harvest its first crop in May of 2013 and will be available for distribution world-wide.

See Morihiro Onodera April 23, 2014 at “The Science of Sushi”

What hooked you on cooking?: The desire to want to eat and taste delicious food.

The coolest example of science in your food?: My basic approach to cooking is to think about the natural ingredients and the climate (seasons) of its origin, ingredients that are kind to the body and to earth—a very simple-minded attempt with natural science at its core.

The food you find most fascinating?: I’m always seeking the true flavor of a given ingredient—that’s what fascinates me.

What scientific concept–food related or otherwise–do you find most fascinating?: Natural science.

Your best example of a food that is better because of science?: Konbu and natural salt.

How do you think science will impact your world of food in the next 5 years?: It will be interesting to see how the true flavors of ingredients change over time—how natural science will affect that change. Simultaneously, I will continue my studies in discovering and knowing what’s kind for the human body and our earth.

One kitchen tool you could not live without?: Rice cooker, including donabe (Japanese clay pot).

Five things most likely to be found in your fridge?: Fresh local vegetables, miso, umeboshi (pickled plum), homemade yuzu kosho (pepper), and leftover cooked brown rice. Outside of the fridge: dry goods, salted bran (used for pickling), rice, oil (sesame and olive), salt, konbu.

Your all-time favorite ingredient?: Rice.

Favorite cookbook?: Book series by Rosanjin (Kitaoji Rosanjin, Japanese artist and epicure).

Your standard breakfast?: Black tea (straight). Seasonal, local fruits. Bread or hot rice cereal. Sometimes eggs (steamed) cooked with sautéed spinach.

Ole G. Mouritsen

April 8, 2014/in Profiles/by Grant Alkin

Ole G. Mouritsen is a professor of molecular biophysics at the University of Southern Denmark. His research concentrates on basic science and its practical applications to biotechnology, biomedicine, gastrophysics, and gastronomy. He is an elected member of the Royal Danish Academy of Sciences and Letters, The Danish Academy of Technical Sciences, and the Danish Gastronomical Academy. His books include Life: As a Matter of Fat; Sushi: Food for the Eye, the Body, and the Soul; Seaweeds: Edible, Available, and Sustainable and Umami. Unlocking the Secrets of the Fifth Taste.

See Ole G. Mouritsen April 23, 2014 at “The Science of Sushi”

What hooked you on science? On food?: Science: Curiosity, in particular in the history of natural sciences (thermodynamics, statistical physics). Food: A combination of a continuously growing interest in cooking, a liking to eat good and challenging food (in particular Japanese food), a challenge to apply science principles to food and cooking, as well a deep interest in using food and taste as a vehicle for science communication.

The coolest example of science in your food?: Access to foodstuff from the ocean as a prime source for unsaturated essential fatty acids together with the invention of cooking for producing soft food as key driving forces for human evolution. Next to that, dairy products have a wonderful science content.

The food you find most fascinating?: Almost all traditional Japanese food, because of the combination of its cultural history, deliciousness, aesthetic looks, freshness, and bounty of good stuff from the ocean.

What scientific concept–food related or otherwise–do you find most fascinating?: Self-assembly and interface-active compounds.

Are there any analogies you like to use to explain difficult or counter-intuitive food science concepts?: I have found that a pacman analogy is a great way of making people understand the secrets of the synergy in the umami taste sensation. Not really counter-intuitive, but somewhat surprising and good to understand better what you already know.

How does your scientific knowledge or training impact the way you cook? Do you conduct science experiments in the kitchen?: I am an intuitive cook in my own kitchen and I have no patience for recipes, and hence never use cookbooks. Sometimes I ask science questions, but in most cases cooking to me is more like performing music (not that I know since I am not a musician). Also, the kitchen for me is a place for mental repair and relaxation, the foreplay being shopping at food markets.

One kitchen tool you could not live without?: My Japanese all-purpose kitchen knife.

Five things most likely to be found in your fridge?: Skyr (or yoghurt), a selection of tsukemono, marinated herring, miso, yuzu juice, and dried/smoked/aged sausages.

Your all-time favorite ingredient?: Avocado.

Favorite cookbook?: I have no favorite cookbook (don’t care much for cookbooks). My favorite food-related book is no doubt McGee’s On Food and Cooking.

Your standard breakfast?: At home, always skyr (or yoghurt), home-mixed basis muesli with no dried fruit but always with roasted buckwheat, topped with a sip of fresh orange juice and possibly some fresh blueberries, if in season. To drink, fresh orange juice with as much pulp I can get and black tea. When traveling, I am an omnivore and prefer to eat like the locals.

Science & Food 2014 Undergraduate Course

April 1, 2014/in Course Lectures/by Grant Alkin

This week marks the beginning of UCLA’s Spring Quarter, which can only mean one thing… It’s time for the Science & Food undergraduate course! We have a stellar lineup of chefs and farmers slated for our third annual offering of Science & Food: The Physical and Molecular Origins of What We Eat. Although the course is only open to current UCLA students, we will be posting highlights from the course right here on the blog. Until then, check out this year’s course speakers and brush up on some of the great science we’ve learned in past courses.

And don’t forget: the Science & Food 2014 Public Lecture Series is fast approaching, so be sure to get your tickets before they sell out. Hope to see you all there!

2014 Science & Food Course Lecturers

The Molecules of Food
Eve Lahijani, UCLA School of Public Health

Why Carrots Taste Sweeter in the Winter
Ashleigh Parsons, alma
Ari Taymor, alma
Brian D. Maynard, alma
Courtney Guerra, Courtney Guerra Farms

Molecules from Soil to Plants
Ernest Miller, Master Food Preservers of Los Angeles County

Self-Assembly: From Proteins and Lipids to Cheese
Ole Mouritsen, University of Southern Denmark

Apple Pie 101
Daryl Ansel, UCLA Dining Services

Why Lettuce is Crispy
Andrea Crawford, Kenter Canyon Farms

Meat Texture and Elasticity
Ari Rosenson, CUT

Viscosity: From Physiology to Pie Filling
Nicole Rucker, Gjelina Take Away

Microbes in Food
Alex Brown, Gourmet Imports

The Physiology of Taste
Juliet Han, Espresso Republic

Highlights From Past Science & Food Courses

Why Are Root Vegetables Sweeter in Cold Weather? – Alex Weiser, Weiser Family Farms

Milk: From Breast to Cheese – Dan Drake, Drake Family Farms

The Molecules of Food and Nutrition – Dr. Dena Herman, UCLA Fielding School of Public Health

Viscosity in French Sauces – Josiah Citrin, Mélisse

It’s All About Sugar – Barbara Spencer, Windrose Farm

The Molecules of Food– Jordan Kahn, Red Medicine

Pizza Nanophysics & The Bacon Genome

March 27, 2014/in What We're Reading/by Grant Alkin

As we saw earlier this week, scientific progress can collide with the food world in some truly unexpected ways. Continuing this theme, pizza tossing helps nanophysicists design tiny motors, while pig genome research holds the key to tastier bacon. Read more

Sky-High Spuds

March 25, 2014/in News & Views/by Grant Alkin

In the not-so-distant future, surfing the web at 35,000 feet will be just as reliable as going online at your favorite coffee shop. Who do we thank for this aeronautical innovation? Teams of engineers have been leading the charge to bring us quality in-flight internet, but there’s another WiFi hero you probably didn’t expect… potatoes!

Photo credit: Boeing

Providing strong and consistent WiFi throughout a crowded airplane cabin presents an interesting challenge. Because the human body can interfere with WiFi signals, a cabin full of passengers can wreak havoc on an otherwise stable internet connection. But running rigorous WiFi tests on a full, airborne flight is impractical. And holding passengers hostage for days in a grounded airplane cabin is just unthinkable.

Enter the potato. Potatoes and humans have comparable dielectric properties, meaning that they similarly interact (and interfere) with WiFi signals. Engineers at Boeing used this to their advantage, creating a new way to test the quality of airline WiFi sans humans. The aptly named “project SPUDS” (Synthetic Personnel Using Dielectric Substitution) used 20,000 pounds of potatoes to quickly optimize the effectiveness and safety of WiFi signals aboard decommissioned airplanes.

When this breakthrough hit newsstands back in 2012, Boeing made it clear that potatoes weren’t in their original plan. In reality, SPUDS serendipitously took off when the research team stumbled across a paper from the Journal of Food Science describing the dielectric properties of 15 fruits and vegetables.

It turns out that food scientists have been studying the dielectric properties of fruits and vegetables for quite some time, as these properties determine how foods behave in a microwave oven. Dielectric properties describe how materials interact with electromagnetic waves, including those emitted by microwave ovens. In particular, dielectric properties determine how much energy a food can absorb in a microwave oven and how far into the food the microwaves will penetrate. Such information is especially useful to industrial food processors who often use microwaves to cook, pasteurize, dry, or preserve various food products.

WiFi signals are typically transmitted at a frequency (2.40 GHz) that is remarkably close to the frequency produced by microwave ovens (2.45 GHz). Thanks to the work of food science researchers, Boeing engineers could confidently choose the potato as their ideal human stand-in.

Thinking about this story, it’s hard not to marvel at the interconnectedness of science. Those food scientists probably never imagined that their work would eventually help improve internet access. And those Boeing engineers must have been pretty surprised to find themselves perusing the latest in food science research. It can be difficult to predict where our ongoing pursuit of knowledge will lead us, but one thing is clear—when it comes to expanding our view of science and making new connections, the sky’s the limit.

Read the paper: Sipahioglu O & Barringer SA (2003) Dielectric Properties of Vegetables and Fruits as a Function of Temperature, Ash, and Moisture Content. J Food Sci 68: 234–239.

About 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

Fancy Chocolate Treats

March 4, 2014/in DIY Kitchen Science/by Grant Alkin

Photo credit: Jesús Rodriguez (hezoos/Flickr)

Chocolate-covered strawberries have an innate beauty in their simplicity, making this snack both sweet and decadent. But this gourmet treat does not have to be expensive nor only savored at special events. Although it’s not quite as simple as dipping strawberries into soupy chocolate sauce, you can easily make chocolate-covered strawberries in your very own kitchen with a basket of strawberries, a bag of chocolate, and a little patience.

To perfect the crafting of chocolate-covered strawberries, it helps to first consider the composition of chocolate. Chocolate contains only a few ingredients: fat, sugars, proteins, and soy lecithin as emulsifier that holds everything together [1,2]. Cocoa butter, a fat that is derived from cocoa beans, makes up the majority of chocolate. Like many vegetable fats, cocoa butter is a mixture of fatty molecules called triacylglycerols. Different types of triacylglycerols—saturated, monounsaturated, polyunsaturated—have their own thermal and structural properties. Roughly 80% of cocoa butter are monounsaturated triacylglycerols [3]. The secret to chocolate perfection lies in the microscopic arrangement of these molecules. The texture (smooth vs. lumpy), appearance (glossy vs. dull), and melting temperature of chocolate (in your mouth at 98°F vs. in your hand at 82°F) all depend on how triacylglycerols pack together in the finished chocolate product.

Triacylglycerols are elongated, spindly molecules that can be packed together in different ways, sort of like long, skinny Legos. The three main ways that triacylglycerols can pack together are named α, β’, and β [3]. A pure mixture of triacylglycerols will form the most stable structure, β [4], and quality chocolate that is hard, smooth, and shiny will predominantly contain this β structure. Unfortunately, cocoa butter isn’t purely one type of triacylglycerol: while the 80% monounsaturated triacylglycerols will tend to pack together nicely into perfect β structures, the other 20% of cocoa butter fat molecules can interfere and lead to less stable α or β′ structures. As shown in Table 1, chocolate can take on different combinations of α, β′, and β structures, categorized in order of increasing stability as crystals I-VI [2,3]. Crystal V possesses only the β structure, and so it boasts the most desirable chocolate characteristics, such as good sheen, satisfying snap, and melt-in-your-mouth smoothness.

Table 1. Properties of chocolate crystals (adapted from [2]).

Crystal	Structure	Melting Temp (°F)	Chocolate Characteristics
I	β′sub(α)	63	Dull, soft, crumbly, melts too easily
II	α	70	Dull, soft, crumbly, melts too easily
III	β′2	79	Dull, firm, poor snap, melts too easily
IV	β′1	82	Dull, firm, poor snap, melts too easily
V	β2	93	Glossy, firm, best snap, melts near body temp
VI	β1	97	Hard, takes weeks to form

Unfortunately, getting chocolate to form the desired crystal type is easier said than done. When chocolate is melted and then left alone to re-harden on its own terms, uncontrolled crystallization occurs: any and all of the six crystal types will form at random. Chocolate that has been allowed to set this way ends up clumpy and chalky. To control crystallization and select for crystal V, the chocolate must be tempered. Through the tempering process, chocolate is first heated to 110-130°F to melt all the different crystal types. Most importantly, the temperature has to be higher than 82°F to melt the inferior crystals I-IV. Melted chocolate is then cooled down by adding “seeds” of chocolate that already contain only crystal V. These seeds are usually just pieces of chocolate that has already been tempered. Any piece of chocolate—chips, buttons, or chopped— can be used, as the majority of chocolate on the market has already been tempered. These seeds slowly cool the melted chocolate and act as a molecular template from which additional crystal V structures can grow [3]. As the chocolate cools, the stable crystal V will come together into a dense, even network, creating that lustrous, firm chocolate coating.

But beware: a drop of water can ruin all that hard work and perfectly tempered chocolate by causing it to seize. During the manufacturing process, water is removed from the chocolate, leaving behind a blend of fats and sugars. Introducing water to melted chocolate causes the sugar molecules to clump together in a process known as seizing [1]. These wet, sticky sugar clusters result in a grainy, thick batch of chocolate.

Seizing can happen when chocolate is melted in a double boiler, as water from the steam can get into the chocolate. It can also happen when pockets of chocolate are accidentally burnt. Burning is a chemical reaction that oxidizes the fats and sugars to produce carbon dioxide and water. Water that forms in the burnt pockets of chocolate will cause the rest of the batch to seize. But have no fear! Seized chocolate is not completely ruined: it can be saved by adding even more water or other liquids such as cream. Though it may seem counterintuitive, adding more water actually dissolves the sugar clumps, breaking them apart so that the chocolate can become smooth and creamy again [1]. Unfortunately, because there is now moisture in the chocolate, it will not dry and harden into a chocolate shell anymore. Chocolate rescued in this way can be used for hot chocolate, icings, fillings, or ganaches, which means you can still make an impressive chocolate treat even if the chocolate-covered strawberries don’t work out.

Chocolate-Covered Strawberries

1 lb. strawberries
16oz milk chocolate chips
Thermometer (optional, but would be helpful)

1. Melt half to two-thirds of the chocolate chips…

…In a double boiler: Stir constantly. Be sure steam doesn’t escape and sink into the chocolate. Do not cover.

…In the microwave: Heat on high 1 minute. Do not cover. Remove from the microwave and stir. If all the chocolate has not melted, heat again for 5-10 seconds. Repeat until completely melted
Note: If possible, avoid using a heat-retaining container like glass, which may burn the chocolate. Plastic is preferred.

2. Once completely melted, carefully continue heating until the temperature is 90-95°F.

3. Remove from heat, then add chocolate chips. Stir until the chips have melted and the chocolate is 82-88°F.

4. To test if the chocolate is ready, spread a thin layer on the back of a spoon or a piece of paper. It should harden in less than 3 minutes. If it doesn’t, stir in more chocolate chips.

5. When the chocolate is ready, carefully dip in strawberries. Make sure the strawberries are dry, before dipping. Allow dipped strawberries to dry on a sheet of parchment paper.

References Cited

Corriher, S. Chocolate, Chocolate, Chocolate. American Chemical Society: The Elements of Chocolate. October 2007; <http://acselementsofchocolate.typepad.com/elements_of_chocolate/Chocolate.html>
Loisel C, Keller G, Lecq G, Bourgaux C, Ollivon M. Phase Transitions and Polymorphism of Cocoa Butter. Journal of the American Oil Chemists’ Society. 1998; 75(4): 425-439.
Rowat A, Hollar K, Stone H, Rosenberg D. The Science of Chocolate: Interactive Activities on Phase Transitions, Emulsification, and Nucleation. Journal of Chemical Education. January 2011; 88(1): 29-33.
Weiss J, Decker E, McClements J, Kristbergsson K, Helgason T, Awad T. Solid Lipid Nanoparticles as Delivery Systems for Bioactive Food Components. Food Biophysics. June 2008; 3(2): 146-154

About 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.