Flavor without the Calories: Scientists Create a Digital Taste Simulator

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Think of any task and chances are someone is developing a new mobile electronic device for it. Technologies exist that pay for your coffee, track your UV light exposure, and even drive your car, but can one also simulate flavor? With that question in mind, scientists led by Nimesha Ranasinghe at the National University of Singapore are developing a device that can scintillate your tongue with sour, bitter, salty, and sweet tastes without the use of any chemicals or actual food.

The “Tongue Mounted Digital Taste Interface” uses a two-probe system to send electrical and thermal signals to the tongue to produce taste. By altering the magnitude of the electric currentA (20 – 200 mA), frequency of electric pulsesB (50-1000 Hz), and temperature (20 – 35 °C [68 – 95°F] ), the interface changes the flavor profile and intensity the wearer experiences. For example, increasing the magnitude of the electrical current strengthens sour, bitter, and salty sensations1.

Tongue_interface

Figure 1: Schematic of the Tongue Interface1

device_tongue

Figure 2: Interface applied to tongue1

To understand how this system works, you have to first understand the anatomy of a taste bud (Figure 3).

Taste_bud

Figure 3: Diagram of a Taste Bud2.

When food enters the mouth, it is broken by chewing and mixed with saliva, which dissolves small food molecules like salts and sugars. These small molecules enter the taste pore and react with taste receptor cells. These taste receptor cells activate attached nerves, which transfer electrical signals to the brain that transmit the sensation of taste. In other words, a molecular signal is converted into an electrical one. Direct stimulation of taste receptors with electricity bypasses the need for initiating the signal using molecules and directly triggers signals to the attached nerves cells, which produce taste. This is supported by research that shows electric stimulation of the tongue alone has produced sour, bitter, and salty sensations2.

In addition to an electrode, a temperature probe was also included, as changing temperatures can trigger taste sensations. For example, a previous study found that warming the front of the tongue evoked a sweet sensation, while cooling caused a salty/sour taste3. These scientists suggested this property of taste might be part of the hard wiring of the taste bud because the reverse had been shown to occur. Temperature specific nerve cells in the mouth were shown to respond to bitter and sour substances. Therefore, if temperature receptors can respond to taste, then taste receptors may also react to temperature.

While this technology is still in its infancy, it has the potential to enhance the overall gastronomic experience. Movies, video games, and TV shows could have flavor simulators that immerse your sense of taste into their world. Alternatively, chefs might be able to share the flavors of their dish remotely with patrons in the comfort of their own homes. Whatever its ultimate use, Nimesha Ranasinghe and his team’s work challenges our expectations of how flavor can be experienced and encourages others to push the boundaries of how new technologies interact with food.

Learn more about Digital Taste Interface

http://www.nimesha.info/digitaltaste.html#dti

 

References Cited

  1. Ranasinghe, N. et al. 2012. Tongue mounted interface for digitally actuating the sense of taste. 2012 16th Annual International Symposium on Wearable Computers (ISWC): 80-87
  2. Chandrashekar, J. et al. 2006. The receptors and cells for mammalian taste. Nature 444 (7117): 288-294
  3. Plattig, K. and Innitzer, J. 1976. Taste qualities elicited by electric stimulation of single human tongue papillae. Pflugers Archive European Journal of Physiology 361(2):115–120
  4. Cruz, A. and Green, B. 2000. Thermal stimulation of taste. Nature 403 (6772): 889-892.

Footnotes

  • A altering the magnitude of the electric current: The electric current, a measure of the flow of electric charges across a surface, is measured in amperes. A portable hearing aid is powered by about 0.7 microamperes, which is 3.5 times higher than the upper range of the taste electrode.
  • B frequency the electric pulses: The frequency of electric pulses is measured in hertz, which is defined as cycles per second. It is standard for the electricity (AC current) that you receive from an outlet in the US to operate at 60 Hz.

Vince ReyesAbout the author: Vince C Reyes earned his Ph.D. in Civil Engineering at UCLA. Vince loves to explore the deliciousness of all things edible.

Read more by Vince Reyes

Cardamom

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Green & Black Cardamom

Photo Credit: Robin (FotoosVanRobin/Flickr)

Cardamom is the third most expensive spice by weight, behind only saffron and vanilla. But with a captivatingly complex flavor profile crammed into such a small package, there’s little mystery behind its steep price. This spice delivers a pungent taste that’s smokey, yet contains hints of coolness reminiscent of mint and lemon, packed inside the tiny black seeds of the small cardamom seed pod. The cardamom genera belong in the ginger family, Zingiberaceae. True cardamom, also known as green cardamom, falls within the genus Elettaria and is grown in India and Malaysia. Black cardamom is of the genus Amomum and grown primarily in Asia and Australia.

While popular in foods and drinks, cardamom is equally admired in traditional medicine. Therapeutic uses range from antiseptic, expectorant, stimulant, and tonic [1]. Cardamom oil is especially known to help alleviate digestive system problems, working as a laxative, colic, stomachic, and diuretic [1]. Perhaps most interesting is its airway relaxant potential in the treatment of asthma [2]. Cardamom contains flavenoids, which exhibit bronchodilatory activity, essential to asthma relief by relaxing constricted bronchial tubes [2]. Moreover, cardamom extracts were observed to relax carbachol- and potassium-induced contractions in tracheal tissues [2], effectively relieving bronchospasms in asthma attacks. Bronchospasms occur in instances of high levels of carbachol or potassium, which are able to cause tracheal tissue contractions by simultaneously opening L-type calcium channels and stimulating muscarinic receptors. Both calcium channels and muscarinic receptors regulate signals for smooth muscle thickening; carbachol and potassium interaction with these signaling pathways leads to airway constrictions. In the study, cardamom showed inhibitory effects against carbachol and potassium, enabling relaxation of the contracted tissues.

Whether the ailment is asthma, digestive problems, or simply thirst, cardamom is all the more reason to enjoy a spicy cup of masala chai.

References cited

  1. “Cardamom Essential Oil (a.k.a. Cardomon Essential Oil) Information.”Cardamom Oil (Elettaria Cardamomum). N.p., 29 May 2014.
  2. Khan A, Khan Q, Gilani A. Pharmacological Basis for the Medicinal Use of Cardamom in Asthma. Bangladesh Journal of Pharmacology. June 2011;6(1):34-37.

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

Harnessing Creativity & The Science of Pie (Event Recap)

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On your mark…
Get set…
GO!

As the doors swung open, guests eagerly awaiting the final Science & Food lecture series were transported to a place nothing short of a Pie-Palooza. Twenty student teams stood confidently next to their baked confection and explained to the judges how they employed the scientific method to creatively reimagine the art of baking the perfect pie. Some developed aqueous solutions to modify the flakiness of their pie crusts while others sought to improve filling texture by altering pH levels and used techniques such as microscopy to measure their results. Whatever their approach, the students proved that a little bit of science goes a long way in mastering the craft of pie baking.

Dr. Paul Barber (Associate Professor, UCLA) and Dave Arnold carefully evaluate the students pie presentations

Dr. Paul Barber (Associate Professor, UCLA) and Dave Arnold carefully evaluate the student pie presentations

Special guest judges, Nicole Rucker of Gjelina Take Away and food critic, Jonathan Gold

Nicole Rucker (Pastry Chef, Gjelina Take Away) and Jonathan Gold (Food Critic, LA Times) partner up as special guest judges


Lena Kwak and Dr. Rachelle Crosbie-Watson (Associate Professor, UCLA) take a closer look at student posters

Lena Kwak and Dr. Rachelle Crosbie-Watson (Associate Professor, UCLA) take a closer look at student posters

After the large-scale pie tasting, guest speakers, Lena Kwak and Dave Arnold, took the stage to share their insight on innovation in the culinary laboratory and emphasized how unforeseen mishaps often lead to novel discoveries. Co-Founder and President of Cup4Cup, Kwak discussed how her breakthrough formulation of gluten-free flour was a by-product of her fearlessness to try new techniques and make mistakes in the kitchen. Founder of the Museum of Food and Drink (MOFAD) and Owner of Booker & Dax, Arnold described how curiosity and relentless dedication to experimentation led to the development of many of his out-of-the-box culinary gadgets. Case in point: the Searzall, one of his latest inventions designed for hand-held blowtorches to evenly apply high temperature heat to sear foods while avoiding the remnants of unpleasant aromatics. He also invoked the audience to participate in an experiment where he challenged everyone to digest gymnemic acid, which dulls our sensory perception of sweetness. This exercise was designed to help guests unlock and appreciate the other factors (such as texture) that contribute to our understanding of taste.

Kwak addresses the audience's questions and reveals some of ingredients in her gluten-free flour

Kwak addresses the audience’s questions and reveals some of ingredients in her gluten-free flour


Dave Arnold explains his investigative process to developing his newest product, Searzall

Arnold explains and demonstrates the evolutionary process involved in developing the Searzall


Gymnemic acid, a sweetness inhibitor, made this bag of sweets taste completely bland!

Gymnemic acid, a sweetness inhibitor, made this bag of sweets taste completely bland

Finally, the panel of special guest judges shared with the audience their favorite pies from the student entries and awarded the students with prizes for the “Most Creative Pie”, “Most Qualified to Enter a Real Pie Contest”, “Best Scientific Pie”, “The People’s Choice Pie”, and “Best Overall Pie”.

Tom Folker and Eric Hirshfield-Yamanishi take home the "Most Qualified to Enter a Real Pie Contest" prize

Tom Folker and Eric Hirshfield-Yamanishi take home the “Most Qualified to Enter a Real Pie Contest” prize

Folker and Hirshfield-Yamanishi explored the effect alcohol, specifically Fireball whiskey, had on the overall flakiness of their pie crust and produced a pie the judges thought was worthy of a professional pie contest.

The "Most Creative Pie" went to Ying Zhi Lim and Jen So for their rosemary-infused deconstructed apple pie

The “Most Creative Pie” went to Ying Zhi Lim and Jen So for their imaginative apple pie

These creative young women, Lim and So, took the competition to the next level by presenting a deconstructed, rosemary-infused apple pie topped with a “reverse spherified” lemon zest cream cheese sauce to a create a harmoniously balanced and flavorful treat.

Christina Chung, Tori Schmitt, and Elliot Cheung impressed the judges and won the "Best Scientific Pie" award

Christina Chung, Tori Schmitt, and Elliot Cheung impressed the judges and won the “Best Scientific Pie” award

Chung, Schmitt, and Cheung added different combinations of liquids to generate their pie crust and recorded the amount of force required to alter the elasticity of the baked crust. Ultimately, the incorporation of beer into their pie crust recipe significantly altered texture as measured and quantified by the elastic modulus.

Apple Queens, Alina Naqvi and Ashley Upkins-Scott, stole the show and won both "The People's Choice Pie" and "Best Overall Pie" prize

Apple Queens, Alina Naqvi and Ashley Upkins-Scott, stole the show and won both “The People’s Choice Pie” and “Best Overall Pie” prize

Naqvi and Upkins-Scott of team Apple Queens took different varieties of apples, including Granny Smith, Red Delicious, Pink Lady, and Fiji, to produce a crumble top pie that garnered praise from both the audience and the judges.

Congratulations to all the winners!

All photos were captured by Patrick Tran. For more images from the event, visit this photo album.

Anthony MartinAbout the author: Anthony Martin received his Ph.D. in Genetic, Cellular and Molecular Biology at USC and is self-publishing a cookbook of his favorite Filipino dishes.

Read more by Anthony Martin

Gluten Tolerance

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photo credits (whatsername?/flickr)

It seems that people love to hate gluten. Though it plays an important role in baking, gluten has a bad reputation. The market for gluten-free foods and beverages reached $4.2 billion in 2012; an increase of 28% since 2008.[1] It is actually difficult to go into Whole Foods and find a baking mix with gluten. But gluten isn’t necessarily bad; it’s just misunderstood. Have a heart, and let’s learn to better appreciate gluten for the remarkable protein network that it is.

Gluten is comprised of two proteins; gliadin and glutenin, that are conjoined with starch in the endosperm of various grass-relatedgrains. Endosperms of flowering plants are stored with protein to nourish embryonic plants during germination.[2] True gluten is typically defined as coming only from certain members of the grass family, namely wheat, but gluten may arise from other cereal grains, like barley and rye, as they also contain protein composites of similar proteins. When water and flour mix, glutenin molecules cross-link with gliadin, and form a sub-microscopic gluten network. Stirring and kneading help gluten stretch and organize into a stronger network, turning simple paste into dough. If dough is leavened with yeast, the fermenting microbes produce carbon dioxide bubbles that are trapped within the gluten network and cause the dough to rise. Baking dehydrates the dough as the protein foam structure solidifies.

The development of gluten affects the texture of baked goods. Kneading promotes the formation of gluten strands and cross-links, creating baked products that are chewier the longer you knead the dough, such as pizza crust and bagels. Less developed gluten yields tender pastry products. For this reason, bread flours are high in gluten, while pastry flours have a lower gluten content. When a tender, flaky product is desired, like a pie crust, a fat such as shortening can be used to inhibit cross-link formation, along with less kneading and low moisture content.

photo credits (Andrea_Nguyen/flickr)

photo credits (Andrea_Nguyen/flickr)

Gluten intolerance has recently become a very talked-about condition. The most prominent form of intolerance occurs in people with Celiac disease. When people with this disease eat foods containing gluten, their immune system produces antibodies, which damage the intestinal lining, causing inflammation and nutrient malabsorption. The cause of the disease is currently unknown. Some gene mutations seem to increase risk of developing Celiac, but not everyone with the mutation is gluten intolerant. A study published in the American Journal of Gastroenterology states that the prevalence of Celiac disease in the US is 0.71%. [4] Recently, another potential form of intolerance called non-celiac gluten sensitivity has garnered attention. After consuming gluten, people with gluten sensitivity may experience diarrhea, fatigue and joint pain, but their intestines are not damaged as would be in the case of Celiac. In 2011, this condition was lent credibility by Peter Gibson, a professor of gastroenterology at Monash University and director of the GI Unit at The Alfred Hospital in Melbourne, Australia, who published a study that found gluten to cause gastrointestinal distress in patients without Celiac disease.[5] The experiment was one of the strongest pieces of evidence to date that non-celiac gluten sensitivity is a genuine condition. However, his study had not revealed why his subjects reacted adversely to gluten. He resolved to rigorously repeat the trial, ensuring that no confounding factors affected the results.

The study was conducted as follows: A total of 37 subjects, all meeting the criteria for having non-celiac gluten sensitivity were provided every meal for the entire study period. Any and all potential dietary triggers were removed, including lactose, certain preservatives, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs. They were first fed a baseline diet low in FODMAPs for two weeks, then were given one of three diets (high gluten, low gluten, or placebo). Each subject cycled through each diet, and none ever knew what specific diet he or she was eating.

Regardless of which diet they were on, subjects reported similar degrees of worsened gastrointestinal ailments. Their reported pain, bloating, nausea, and gas all increased over the baseline diet. The data clearly indicated that a nocebo effect was occurring – in other words, participants were experiencing an entirely psychological phenomenon in which a harmless substance causes a harmful effect.

"A celiac looking in the window of a Parisian boulangerie." photo credits (justmakeit/flickr)

“A celiac looking in the window of a Parisian boulangerie.” photo credits (justmakeit/flickr)

So whether you eat gluten, cannot eat gluten, or choose to avoid it, it is a scientifically interesting substance that has spurred quite a bit of talk and research. Perhaps gluten is damages us psychologically more than it does health-wise. Despite the possibly nocebic effects of gluten, the booming popularity of gluten-free products has allowed people with Celiac a much greater range of food options, and has encouraged people to examine the ingredients of their foods more closely, though they may be avoiding the wrong substance.

Sources

1. “Gluten-Free Foods and Beverages in the U.S., 4th Edition.” : Market Research Report. N.p., n.d. Web. 31 May 2014.

2. Castro, By Joseph. “What Is Gluten?” LiveScience. TechMedia Network, 17 Sept. 2013. Web. 28 May 2014.

3. “Celiac Disease.” Web log post. Webmd.com. N.p., n.d. Web.Pomeroy, Ross. “Non-Celiac Gluten Sensitivity May Not Exist.” RealClearScience. N.p.,

4. Rubio-Tapia, A., JF Ludvigsson, TL Brantner, JL Murray, and JE Everheart. “The Prevalence of Celiac Disease in the United States.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 25 May 2014.

5. Biesiekierski JR, Peters SL, Newnham ED, Rosella O, Muir JG, Gibson PR. “No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates.” Gastroenterology.

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.

Read more by Elsbeth Sites

Cinnamon

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Cinnamon

Photo credit: Hans Braxmeier (Hans/Pixabay)

Sweet and spicy, cinnamon is one of the oldest spices known to humans; it is also a favorite topping or secret ingredient in both sweet and savory recipes. This warm spice is obtained from the dried inner bark of several species of trees within the Cinnamomum genus. True cinnamon however, sometimes known as Ceylon cinnamon, comes from C. verum (also, C. zeylanicum, the antiquated botanical name for the species), indigenous to Sri Lanka. Other Cinnamomum species that are cultivated for commercial purposes are C. burmannii (Indonesian cinnamon), C. loureiroi (Saigon cinnamon or Vietnamese cinnamon), and C. cassia (Cassia or Chinese cinnamon) [1].

Analysis of the fragrant essential oil from cinnamon bark reveals the main compound responsible for the sharp taste and scent of cinnamon comes from cinnamaldehyde (also known as cinnamic aldehyde). Since its identification in 1834 by French scientists, Jean-Baptiste Dumas and Eugene Péligot, cinnamaldehyde has been found to be a rather useful molecule outside of the spice rack. Studies have suggested that cinnamaldehyde has antioxidant properties, which makes it a promising anticancer agent [2]. Further, cinnamaldehyde has been shown to work effectively as pesticide, fungicide, and antimicrobial agent [3].

Of course, one of the most useful properties of cinnamaldehyde is making apple pies extra delicious.

Cinnamaldehyde-04

References cited

  1. Culinary Herbs and Spices. The Seasoning and Spice Association.
  2. Nagle A, Fei-Fei G, Jones G, Choon-Leng S, Wells G, Eng-Hui C. Induction of Tumor Cell Death through Targeting Tubulin and Evoking Dysregulation of Cell Cycle Regulatory Proteins by Multifunctional Cinnamaldehydes. Plos ONE. Nov 2012;7(11):1-13.
  3. Shan B, Cai YZ, Brooks JD, Corke H. Antibacterial Properties and Major Bioactive Components of Cinnamon Stick (Cinnamomum burmannii): Activity against Foodborne Pathogenic Bacteria. Journal of Agricultural Food Chemistry. 2007;55(14): 5484-90

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

5 Things About Apples

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Our third and final lecture, Harnessing Creativity (and the Science of Pie), is coming up fast! At the event, students from the Science & Food undergraduate course will be serving up science and apple pies. To get ready, here are 5 fun facts related to apples:

Apples3

Apples5

Apples1

Apples2

Apples4

Liz Roth-JohnsonAbout 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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Taste Tripping With Miracle Berries

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MiracleBerries

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

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!

MiraculinSour

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.

MiraculinBlocksSweetReceptor

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

  1. Degrace-Passilly P, Besnard P (2012) CD36 and taste of fat. Curr Opin Clin Nutr Metab Care 15: 107–111.
  2. 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.
  3. Yamamoto C, et al. (2006) Cortical representation of taste-modifying action of miracle fruit in humans. Neuroimage 33:1145-1151.
  4. 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.

Eunice LiuAbout 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.

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Follow-Up Q&A with Ole G. Mouritsen

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Onodera, translator, and Mouritsen at Science of Sushi. Photo Credits: (Matthew Kang/Eater)

Onodera, translator, and Mouritsen at Science of Sushi. Photo Credit: Matthew Kang/Eater

The audience present at The Science of Sushi asked our guest lecturers some great questions, and quite a few of them! Unfortunately, there wasn’t enough time to answer them all, but Ole G. Mouritsen has been kind enough to answer some of the lingering questions that went unanswered. Below his responses, we have included some additional information to help quench your thirst for knowledge (and sake).

Q: Are parasites within fish common? Are they a passable health problem?

A: Parasites can be common in some species, e.g., cod, mackerel, herring, and wild salmon. If in doubt, always freeze or marinate fish before eating raw.

The FDA provides guidance under their Parasite Destruction Guarantee on the preparation of raw fish. Fish intended to be consumed raw must be “frozen and stored at a temperature of -20°C (-4°F) or below for a minimum of 168 hours (7 days)”. [1]

Photo Credits: (Antony Theobald/Flickr)

Photo Credit: Antony Theobald/Flickr

Q: What exactly is ‘sashimi/sushi grade’ fish?

A: Fish that can be eaten raw. If in doubt, ask a fishmonger you trust.

 In the United States, the term ‘sushi grade’ is unregulated. However, many suppliers have set up their own parameters for their products, often reserving the term for their most fresh fish.[2]

Photo Credits: (Marla Showfer/Flickr)

Photo Credit: Marla Showfer/Flickr

Q: What are your thoughts on using brown rice in sushi?

A: I don’t myself like brown rice in sushi. If you worry about the calories in white rice, don’t eat sushi.

During the milling process, the germ and bran layer of brown rice are left intact, and are not removed as they are in white rice. The only layer removed is the outermost layer, the hull. Some health-conscious people often opt for brown rice because several vitamins and dietary minerals are lost in this removal process and the subsequent polishing.

Photo Credits: (Thokrates/flickr)

Photo Credit: Thokrates/flickr

Q: What’s your thought on cooking rice with ‘bamboo charcoal’?

A: I don’t understand this question. In principle the source of heating does not matter (except if the cooking pot is open and takes taste from the burning material).

Q: Sake: does it add, hide, or subtract?

A: It is a matter of taste. An old Japanese proverb says that one should not drink sake with rice (too much of a good thing). So drink sake before the sushi meal, or after.

Sake, the alcoholic rice beverage officially known as “Seishu” is defined as one of the following:

  1. Fermented from rice, rice-koji (the mold used to convert the starch in rice into fermentable sugars), and water.
  2. Fermented from rice, water, Sake-Kasu (the lees that remain after pressing Sake; these can still contain fermentable elements), rice-koji, and anything else accepted by law.
  3. Sake to which Kasu has been added.

After any of these processes, the liquid is then strained through a mesh to produce a clear beverage. [3] 

Photo Credits: (atmtx/flickr)

Photo Credit: atmtx/flickr

 

References

  1. “FDA Food Code 2009 – Chapter 3 – Food.” Fda.gov. N.p., n.d. Web. 28 Apr. 2014.
  2. Ransom, Warren. “Sushi Grade Fish.” The Sushi FAQ. N.p., n.d. Web. 28 Apr. 2014. <http://www.sushifaq.com/sushi-sashimi-info/sushi-grade-fish/>.
  3. “Sake.com: Sake Making.” Sake.com: Sake Making. N.p., n.d. Web. 28 Apr. 2014.

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.

Read more by Elsbeth Sites

Texture and Color of Sashimi

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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.

Sashimi 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

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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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