Savoring the Science of Salty and Sweet

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Photo Credit: Joanne Gallagher (Simple Salted Caramels Recipe/Inspired Taste)

Sea salt caramels. Hawaiian pizza. Chocolate-covered pretzels. Salt-and-chili covered mangos. Aside from being delicious snacks, what else do these delectable combinations have in common? They are all quintessential examples of the “sweet and salty” food craze that only continues to rise in popularity in the culinary world as well as the population at large. When combined, these two seemingly contradictory tastes create a unique interplay that heightens the more subtle tastes and brings new complexity to the dish.

Chaudhari, Nirupa, and Stephen D. Roper. “The Cell Biology of Taste.” The Journal of Cell Biology 190.3 (2010): 285-96. Web. 23 Nov. 2014.

Figure 1: The five basic tastes.
Photo credit: Chaudhari, Nirupa, and Stephen D. Roper. (“The Cell Biology of Taste.” The Journal of Cell Biology)

Sweet and salty are two of our five basic tastes (Figure 1). As we’ve previously discussed on the blog, taste is perceived as food is broken down into individual molecules that enter taste pores on the tongue. These molecules then interact with taste receptor cells, which in turn activate nerves that send an electrical signal to the brain to trigger taste perception[1] (Figure 2).

Kibiuk, Lydia V., and Devon Stuart. “Taste and Smell.” BrainFacts.org. 1 April 2012. Web. 10 Dec. 2014.

Figure 2: Taste receptor cells activate nerves that send an electrical signal to the brain.
Photo Credit: Kibiuk, Lydia V., and Devon Stuart. (Taste and Smell/BrainFacts.org)

When we eat, our tongues sense five basic tastes. While this may seem fairly straightforward, it turns out that these five tastes can influence each other. By studying how different pairwise combinations of taste sensations interact, scientists have sought to explain how the five tastes relate to each other on chemical, oral, and cognitive levels [4].

In the case of sweet and salty foods, let’s use an example of chocolate-covered pretzels. Pretzels are characterized by a slightly bitter taste that comes from the lye or baking soda solution the dough is soaked in before baking. (These highly alkaline solutions give pretzels their signature crunch and dark brown color [5].) When dusted with a bit of salt and covered in a layer of chocolate—presto! The pretzel transforms into a delightfully salty-yet-sweet treat without a hint of bitterness. Why does this happen? Sodium has been shown to orally suppress bitterness where it directly interferes with the perception of bitterness in taste pores, a phenomenon sometimes called ‘bitter blocking.’ Instead of directly enhancing sweetness, salt suppresses bitterness and therefore allows the more ‘favorable flavors,’ such as sweet, to shine through [6].

Scientists have also cited that our penchant for sweet and salty has evolved from our primal nutritional instincts. Because our hunter-gatherer ancestors were consistently moving to new areas and eating different plants, those with a distinguishing palate were better able to detect the differences between sweet-tasting high-energy foods and bitter-tasting poisonous foods. Our taste buds are therefore naturally wired to taste sources of energy and possible toxins [4]. This reasoning can be attributed to why we love sweet and salty – sweetness indicates carbohydrates, or energy, while salt is a necessary component in the body’s water balance and blood circulation. Therefore when the flavors are combined, the biological response is increased and our body detects the food as being extra tasty [7].

And even after you taste sweet and salty molecules on your tongue, your stomach continues to sample the molecules and send signals to your brain. This ‘post-oral signal’ can also contribute to the favorable sweet-and-salty response by forming a reward circuit increases our desire for similar tasting foods [8].

Salt’s ability to change the way we perceive taste has established it as an essential enhancer in cuisines worldwide. So the next time you reach for a sweet treat, try adding a dash of salt on top – you never know what surprises it can unearth!

References Cited

  1. Gallagher, Joanne. “Simple Salted Caramels Recipe.” Inspired Taste. 8 Dec. 2012. Web. 23 Nov. 2014.
  2. Chaudhari, Nirupa, and Stephen D. Roper. “The Cell Biology of Taste.” The Journal of Cell Biology 190.3 (2010): 285-96. Web. 23 Nov. 2014.
  3. Kibiuk, Lydia V., and Devon Stuart. “Taste and Smell.” BrainFacts.org. 1 April 2012. Web. 10 Dec. 2014.
  4. Keast, Russell, and Paul A. Breslin. “An Overview of Binary Taste-Taste Interactions.” Food Quality and Preference 14.2 (2003): 111-124. Web. 9 Dec. 2014
  5. Friedrich, Paula. “For a Proper Pretzel Crust, Count on Chemistry and Memories.” NPR. 9 Aug. 2014. Web. 10 Dec. 2014.
  6. Keast, Russell, Paul A. Breslin, and Gary Beauchamp. “Suppression of Bitterness using Sodium Salts.” Chimia: International Journal for Chemistry 55.5 (2001): 441-447. Web. 10 Dec. 2014.
  7. Stuckey, Barb. Taste: Surprising Stories and Science about Why Food Tastes Good. New York: Atria Books, 2013. Print.
  8. Vanderbilt, Tom. “Why You Like What You Like.” Smithsonian Magazine. June 2013. Web. 22 Nov. 2014.

Ashton YoonAbout the author: Ashton Yoon received her B.S. in Environmental Science at UCLA and is currently pursuing a graduate degree in food science. Her favorite pastime is experimenting in the kitchen with new recipes and cooking techniques.

Read more by Ashton Yoon

Engineering the Perfect Gingerbread House

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Building gingerbread houses can be a frustrating process. An idyllic three-story building with crystal sugar snow, marshmallow snowmen, and gumdrop twinkle lights can quickly end in a collapsed mess, sending icing windows and candy cane gates into disarray. But don’t resort to those trusty milk cartons and graham crackers just yet – with a few changes in technique, your dream house can easily be obtained.

gingerbread houses

UCLA students built gingerbread houses at a recent Science & Food event

During our recent “Engineering the Perfect Gingerbread House” event, graduate student Kendra Nyberg taught UCLA students about the best practices for gingerbread construction. Her lecture delved into the molecular makeup of the materials and the physics behind the structure.

Base Construction Materials: Gingerbread and Icing

Gingerbread should be sturdy and demonstrate elasticity, which is the measure of its ability to resist deformation [1]. Because the gingerbread walls will be under stress from the roof, there needs to be sufficient resistance to avoid cracking or total collapse. Dough with a tough, springy consistency and decreased moisture content is ideal, and can be achieved by using flour with high protein content, such as bread flour. Higher-protein flours contain more glutenin and gliadin proteins, which create the springy gluten network that gives dough its elastic properties.

gingerbread houses_fig 1

Photo credit: Ionacolor.com

Icing serves as the glue that holds the entire structure together. The mixture should be just pliable enough to hold the gingerbread pieces together before drying into a hard, unmovable substance. Here egg whites are key. When beaten, the egg’s proteins denature and then coagulate, stabilizing air bubbles in the icing and creating white, foamy “peaks” that vary in their stiffness and resistance to gravity. Stiffer peaks are better for gingerbread icing, and more coagulated proteins can contribute to a stronger paste.

gingerbread houses_fig 2

Photo credit: Advanced Materials

Why use icing instead of frosting? Both confections contain copious amounts of sugar, but where icing contains egg whites, frosting typically incorporates butter. The additional fat globules from butter provide some thickness and stability to the frosting. However, since standard buttercream frosting does not contain egg whites, the only proteins present are those from the milk in the form of butter. Although these proteins are perfect for dense and creamy cupcake topping, they do not assemble into the stiff, strong networks needed for gingerbread house construction.

Stability and Height: Architectural design

Once the bricks and mortar of your gingerbread house have been created, you can move onto the creative part of the process – construction. There are many forces acting on a gingerbread house. Consider the roof: forces on the sloping gingerbread roof includes friction from the frosting, a normal force perpendicular to the gingerbread surface, and gravity pulling the roof toward the floor. These forces also show up to varying degrees in all of the upright walls of the gingerbread house. To avoid collapse, it is best to spread out the forces over many surfaces. For example, a wider structure with a flatter rooftop will be sturdier than a narrow house with a sloping roof.

Normal, friction, and gravity forces acting on a gingerbread roof Photo credit: dallassd.com

Normal, friction, and gravity forces acting on a gingerbread roof
Photo credit: dallassd.com

If the height of the house is very high, the gingerbread is also more sensitive to buckling under the added weight of the extra gingerbread. To prevent buckling, you can calculate the critical height at which buckling occurs, which depends on such factors as gingerbread density and the force of gravity [2].

Photo credit: Tim Jones (Zoonomian)

Photo credit: Tim Jones (Zoonomian)

You don’t have to be an engineer or an architect to construct the perfect gingerbread house. With the proper dough, frosting, and design considerations, the house of your dreams can be achieved – perfect to last as a display through the holidays. Now get building!

References cited

  1. Iona (2011) “Elasticity (TV set art) (3).” blog.ionacolor.com
  2. Tim Jones (2013) “Musings on Structural Gingerbread.”

Catherine HuAbout the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

Read more by Catherine Hu

Hydrogenation

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Photo Credits (flickr/veganbaking,net)

Photo Credits (flickr/veganbaking,net)

For the health-conscious members of society, there are several food fiats: thou shalt avoid high fructose corn syrup, steer clear of ingredients that sound like they could be found in jet fuel, and fear partially hydrogenated oils. Oil in and of itself is not inherently bad; how does adding hydrogen to transform it into the bane of all processed foods?

The general term “hydrogenation” refers to the “reaction of hydrogen with an organic compound.” The term organic compound refers to any molecular compound that contains carbon atoms. The process used to modify oils is technically known as “catalytic hydrogenation,” since it takes place in the presence of a catalyst, which helps speed up the reaction.

Hydrogenation is typically used to improve the flavor stability and keeping qualities of oil. An unhydrogenated oil can turn rancid because its unsaturated carbon atoms are free to bond to oxygen atoms from the air, forming peroxides, which give rancid fats their “off” flavor. Sometimes oils, particularly vegetable oils, are only partially hydrogenated. Complete hydrogenation creates a product containing only saturated fats, which typically has a solid and waxy consistency that is not appropriate for cooking, baking, or eating. Fully hydrogenated vegetable oils would resemble candle wax and have a melting point above 60°C [1].

So how is oil hydrogenated? Typically, a mixture of refined oil and finely powdered nickel (the catalyst) is pumped into a large capacity cylindrical pressure reactor. Heating coils heat the oil to 120-188°C (248-370°F) at 1-6 atmospheres pressure [1]. Hydrogen gas is pumped into the bottom of the reactor, and everything is continuously stirred to distribute the rising gas bubbles throughout the liquid oil. The high temperature, pressure, and the presence of the catalyst ensure that any carbons in the oil that are not at their full hydrogen bond capacity (the “unsaturated” carbons), form new chemical bonds with the hydrogen atoms, thus becoming more and more “saturated” with hydrogen. As they become fully hydrogenated, the oil molecules begin to straighten out and stick to one another, causing the liquid oil to solidify [2].

Screen Shot 2014-12-16 at 9.40.42 AM

What could be so bad about adding hydrogen atoms to oil molecules? With each hydrogen that is added to the molecule, one of the fat’s carbon-carbon double bonds is replaced with two new bonds, each to a hydrogen atom. If we continue this process until there are no more double bonds left, we would have a completely saturated fat. Because saturated fats are more linear, they stack up upon each other all too well, and can increase body cholesterol levels.  If during hydrogenation the fat molecule is left with one or a few double bonds, the molecule takes up either a trans or cis configuration. As you might have guessed, this is how the infamous trans fat comes to be. Both hydrogen atoms occupy the same side of the double bond, forcing the molecule to kink at the bond. In a trans fat, the hydrogens transverse the double bond, and no kink forms. It is a microscopic difference, but one that has profound effects on their biological roles. Several studies have demonstrated that consuming specifically more trans fats increases risk of cardiovascular disease. [5]

Screen Shot 2014-12-16 at 9.55.34 AM

But hydrogenation is not restricted to humans with access to pressure vats. Microorganisms that live in the rumen of cows and other ruminants can “biohydrogenate” fats without any fancy pressure vats or catalysts [3].

Photo Credits (Flickr/Ruud Cuypers)

Photo Credits (Flickr/Ruud Cuypers)

Scientists who study fats have long known that fats in the tissues of ruminants are more saturated than those of nonruminants [3]. Grass and other typical ruminant feedstuffs are rich in unsaturated fatty acids, yet these fats are only present at low concentrations in meat and milk.

When food enters the rumen (essentially a large fermentation vat intended to break down the animal’s fibrous meals), gut microbes catalyze a range of chemical transformations. For example, ruminal microbes transform lipids through both lipolysis and biohydrogenation.

Through lypolysis, microbes break the bonds of long fat molecules, thus producing simpler fatty acids. Unsaturated fatty acids are also biohydrogenized, a process very similar to industrial hydrogenation, but catalyzed by microbes instead of metal [3].

Because of this biohydrogenation, dairy products typically contain 5-10% trans fatty acids [2], which are consumed by anyone who drinks milk or eats butter, tallow, or beef. It is important to note, however, that the predominant trans fatty acid in ruminant fat (vaccenic acid) is not the same as the predominant trans fatty acid produced by hydrogenation of vegetable oil [2]. High consumption of trans fats from industrial hydrogenation are well documented as being linked to cardiovascular disease, while clinical and rodent studies of vaccenic acid have not documented such a strong correlation. [4] These ruminant fats may even protect our hearts from these diseases, but further research is necessary.[5]

Sources:

  1. http://www.joepastry.com/2012/so-how-does-hydrogenation-work/
  2. http://www.soyinfocenter.com/HSS/hydrogenation3.php
  3. http://www.journalofanimalscience.org/content/86/2/397.full
  4. http://www.nrcresearchpress.com/doi/full/10.1139/H09-079#.VI5yBr4mTww
  5. http://onlinelibrary.wiley.com/doi/10.1002/mnfr.201100700/full

 

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

Caramel

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Caramel flavor is a major component of desserts and candies, ranging from smooth, thick sauces to crispy, dark brown glazes of crème brûlées. Through caramelization, a browning process where sugar is heated to around 170 °C and broken down, over 100 compounds are formed that contribute to the color, flavors, and textures of what we know as caramel [1].

Photo credit: APN MJM/Wikimedia Commons

Photo credit: APN MJM/Wikimedia Commons

One simple way to caramelize table sugar is by heating: this process removes water from the disaccharide sucrose (a substance composed of two simple sugars) and breaks it down into monosaccharides fructose and glucose. Next, the monosaccharides react with each other to form new compounds, such as caramelan, caramelen, and caramelin [2]. These compounds aggregate to form brown particles of various sizes due to additional water elimination, contributing to the characteristic brown color of caramel. The stickiness of caramel can be attributed to the ring form of these molecules combined with the presence of free radicals [3]. Further, when in the presence of alkali, sulphite, or ammonia, these compounds can also result in colorants used in food products such as soy sauce and Coca-Cola [4].

In addition to these classic caramel compounds, many other molecules are produced that result in different aromas that contribute to caramel’s complex flavor profile, such as furans (nutty), diacetyl (buttery), maltol (toasty), and ethyl acetate (fruity) [3].

How to tune the flavor of your caramel? The temperature the sugar is heated to determines caramel flavor. “Light caramel” (180°C) can be used for glazes, is rich in flavor, and pale amber to golden-brown in color. By contrast, “dark caramel” (188-204°C) is dark and bitter in flavor due to increased oxidation of the sucrose molecules; it is usually used for coloring. Additional heating past this point will turn the caramel into a black and bitter mess, as the sugar breaks down into pure carbon [2].

Interestingly, caramel candies made with milk or butter do not undergo the caramelization process. Instead, the heating of the dairy product in the recipe causes Maillard reactions between sugar and amines that result in the brown color and flavors produced [1].

Next time you enjoy caramel flavor, you can revel in the smell and taste of all the aromas that result from complex chemical processes. Or, simply make your own with sugar, water, and a stove.

References Cited

  1. “Caramelization.” Accessed 21 October 2014.
  2. “Caramelization.” Accessed 21 October 2014.
  3. “The Chemistry of Caramel.” ScienceGeist. Accessed 21 October 2014.
  4. “E150 Caramel.” Accessed 21 October 2014.

Catherine HuAbout the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

Read more by Catherine Hu

5 Things About Taste

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At our 2014 public lecture How We Taste, Chef Wylie Dufresne, Dr. Dana Small, and Peter Meehan explored the tantalizingly complex concept of flavor. The evening was full of scientific discovery, childhood memories, and culinary innovation. In honor of this enlightening event, here are 5 things you might not know about our sense of taste:

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Gymnemic Acid

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Photo Credits: (flickr/ mutolisp)

Photo Credits: (Flickr/ mutolisp)

Attendees of our Science of Pie event this past spring probably remember sampling gymnemic acid. For anyone who has never tried the bizarre substance, we describe here our first experience with it. Guest speaker Dave Arnold (Founder of the Museum of Food and Drink, and host of the radio show Cooking Issues), supplied everyone in the audience with a small capsule filled with a dusty green powder along with a strawberry, a sugar packet, and small amount of honey. He then instructed everyone to coat the surface of his or her tongue with the mysterious green powder, let it dissolve, and then swallow it. After the unpleasant herbal taste faded away, Arnold told the audience to empty the small sugar packet into his or her mouth. Now, sugar is usually the key to sweet desserts and happiness. But to anyone with a gymnemic-acid coated tongue, eating sugar was like face-planting at the beach and getting a mouthful of sand. The sugar was utterly unsweet. Eating honey felt like taking a swig of thick canola oil. The strawberry became tart and acidic. As the audience quickly realized, gymnemic acid has the peculiar property of inhibiting our perception of sweetness.

Gymnemic acid is precipitated from an aqueous extract of the leaves of Gymnema sylvestre, a tree found in Central and Western India, tropical Africa, and Australia. [1] The leaves of this tree have traditionally been used in Ayurvedic medicine. In fact, the Hindi name for the plant’s derivative, gurmar, means “destroyer of sugar.”[2] Only two other plants are known to have similar taste-altering effects: Bumelia dulcifica, which makes sweet and sour substances taste bitter, and of course the miracle berry of Synsepalum dulcificum, which makes sour things taste sweet. [1]

You may think to yourself, as anyone who has eaten gymnemic acid surely has, inhibiting sweetness is a miserable idea. Why are we manufacturing capsules of this? Gymnemic acid can do more than ruin your dessert. Today it is used to treat metabolic syndrome (a group of risk factors that raise one’s risk of heart disease, diabetes, and stroke), and even malaria. Gymnemic acid is also used to promote weight loss, stimulate digestion, and suppress appetite; it is also prescribed as a diuretic, laxative, and even a snake bite antidote. Gymnemic acid may treat diabetes, as it contains substances that inhibit the absorption of sugar from the intestine and stimulate the growth of cells in the pancreas, where insulin is produced. [2]

While the precise mechanisms of gymnemic acid on taste perception have not been completely elucidated, a few investigations have quantified the effects of gymnemic acid on taste and the timescales over which it operates. To determine the extent to which gymnemic acid diminishes sweet perception, a 1999 study measured the effect of a gymnemic acid oral rinse on taste perception. Their results showed that gymnemic acid reduced the sweetness intensities of sucrose and aspartame to 14% of reported pre-rinse levels. [3] These results also shed light on the timescale of taste alteration: Over a recovery period of 30 minutes, the sweetness intensity values increased linearly to a sweetness perception of 63% of the pre-rinse levels.

Another study performed at Kyushu University in Kukuoka, Japan has also shed some light on the molecular mechanisms underlying the behavior of this odd substance on our tongues. Gymnemic acid is not a pure, unique structure, but is composed of several types of homologues, or compounds of the same general formula. According to these studies, the transmembrane domain of Taste type 1 Receptor 3 (T1R3) is the primary site of the sweet-suppressing effect of gymnemic acids. The acid is predicted to dock to a binding pocket within the transmembrane domain of T1R3. [4] These findings could assist future drug design, and could perhaps lead to the synthesize of more substances that modify receptivity of sweetness. But maybe we should enjoy the wonderful sensation of sweetness as they are.

References cited

  1. Stoecklin, Walter. “Chemistry and Physiological Properties of Gymnemic Acid, the Antisaccharine Principle of the Leaves of Gymnema Sylvestre.” Journal of Agricultural and Food Chemistry 17.4 (1969): 704-08. ACS Publications. Web. 11 Sept. 2014.
  1. “Gymnema: Uses, Side Effects, Interactions and Warnings.” WebMD. WebMD, 2009. Web. 11 Sept. 2014.
  1. Gent, Janneane F., Thomas P. Hettinger, Marion E. Frank, and Lawrence E. Marks. “Taste Confusions following Gymnemic Acid Rinse.” Chemical Senses 24.4 (n.d.): 393-403. Chemse.oxfordjournals.org. Oxford Journals, 1999. Web. 23 Oct. 2014.
  1. Sanematsu, Keitsuke, Yuko Kusakabe, Noriatsu Shigemura, Takatsugu Hirokawa, Seiji Nakamura, Toshiaki Imoto, and Yuzo Ninomiya. “Molecular Mechanisms for Sweet-suppressing Effect of Gymnemic Acids.” Jbc.org. The Journal of Biological Chemistry, 23 July 2014. Web. 11 Sept. 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

Harnessing Creativity

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Harnessing Creativity

Featuring Dave Arnold & Chef Lena Kwak

June 1, 2014

As part of our 2014 public lecture series, Dave Arnold (of Booker and Dax, the Museum of Food and Drink, and the Cooking Issues Podcast) discussed his latest culinary innovations and the role of creativity in food. He was joined by Chef Lena Kwak (of Cup4Cup) who shared her process of invention, research, and discovery in the kitchen.

Check out the highlights or watch the full lecture below.

Lena Kwak on the creation of Cup4Cup and the power of mistakes

“It was working with food that helped me get over the fear of imperfection. Making mistakes in the kitchen played a significant role in my recipe development. I found myself more daring [and] willing to experiment with different flavors and texture combinations…Take Cup4Cup. The original formula took me about year-and-a-half to finalize. A year-and-a-half is a very long time to make a lot of mistakes…. All the knowledge I gained through those mistakes has actually left me with [another] set of different products.”

Her biggest words of advice: “Go out there, makes mistakes—because you never know what those mistakes will lead you to.”

Dave Arnold on how to be creative in the kitchen

“What is important isn’t that you use a piece of technology or that you use a new piece of equipment. Really it’s that you try to understand what is going on while you’re cooking…. It’s to become unhinged in a very analytical way… that’s the whole premise of creativity.”

Dave Arnold uses gymnemic acid to flip our understanding of sweet foods

Dave Arnold gives the audience gymnemic acid to block their sweet taste receptors and then challenges them to try sweet treats like sugar, honey, strawberries and chocolate. He explains that erasing sweetness enables the taster to examine how other factors like texture and acidity influences the experience of sweet foods.

Arnold says this analytical approach to food is important: “Even if you have no idea why something happens, if you have a hypothesis … and you keep adapting and recording what your results are… you can get to the right place.”

Watch the entire lecture:

How We Taste

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How We Taste

Featuring Dr. Dana Small, Chef Wylie Dufresne, & Peter Meehan

May 14, 2014 

As part of our 2014 public lecture series, we explored the concept of taste from the perspectives of a scientist, a chef, and a food writer. Dr. Dana Small described how our brains respond to flavors. Chef Wylie Dufresne of Wd~50 presented his creative approach to generating surprising food flavors and textures.  Peter Meehan shared his experiences with food and taste and how they have shaped his writing, both as a cookbook author and former writer for The New York Times.

Check out the highlights or watch the full lecture below

Wylie Dufresne on Science in the Kitchen and It’s Impact on WD~50

“Cooking is a lot of things and one of the things we discovered was that cooking is a science. There’s certainly some biology. There’s certainly some physics. There’s an awful lot of chemistry at play all the time when you’re cooking… One of the main reasons I opened up WD~50 … was to create a space where I could continue my culinary education, where my staff could continue their culinary education, and where you as a diner, if you so choose, could continue your culinary education.”

Wylie Dufresne on his Aerated Foie Gras 

“How could we, using some very modern technology, walk the idea of a mousse down the road? … Part of the problem with a mousse is that it usually has a lot of stuff in it besides the main ingredient… So what we wanted to do was to figure out if we could create a mousse of foie gras, or if we could aerate foie gras without adding or taking too much away from the flavor.”

Peter Meehan on Developing Taste and Eating Everything

“The first step in developing the taste to become a restaurant critic: Eat … I tried to just each everything… the more I ate the more I understood about food and the more I could draw connections about one thing and another… You start to make these mental points on a map of where flavors are in relation to each other.”

Dr. Dana Small Defines Taste

“There’s molecules and ions in the foods that we eat and they bind to cells on these elongated taste receptors [tastebuds]. When enough binds, the cells get excited. They send a signal to the brain that the brain then interprets as a taste … Taste evolved to detect the presence of nutrients and toxics … You’re born knowing that you like sweet and dislike bitter … because you don’t want to have to learn that sweet is energy and bitter is toxin.”

Dr. Dana Small Defines Flavor and How It’s Different from Taste

“Flavor, on the other hand, preferences and liking for flavors is entirely learned. This has the advantage of allowing us to learn to like available energy sources and learn to avoid particular food items … The flavor allows us to identify a particular item that was associated with a particular consequence that we need to remember… whereas the taste provides just a signal about whether an energy source as in the case of sweet is present.”

Watch the Entire Lecture

Sugar Chemistry of Hard Candies

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Photo Credit: Adam Zivner (Wikimedia Commons)

Photo Credit: Adam Zivner (Wikimedia Commons)

Old-fashioned candy-making is a fascinating spectacle, if one ever gets the opportunity to watch. Fortunately, the Internet is full of videos like this one, which shows how hard candies (specifically, candy canes) are made by hand:

The process that turns ordinary, granulated table sugar into solid, glassy, hard candy is as dynamic on a molecular level as it is captivating to watch on an observable scale.

As a dry ingredient, table sugar comprises granules of sucrose crystals. Transforming these granules into a solid piece of candy begins by dissolving sugar—lots of sugar—in water. When stirred into water, the granules break apart into individual sucrose molecules. Hard candy recipes typically call for 2.5–4 parts sugar in 1 part water. However, sucrose has a solubility of only 2000 g/L, which is roughly 2 cups sugar in 1 cup room temperature water [1]. This is easily remedied by turning up the heat; sucrose solubility increases with temperature, meaning much more sugar can be dissolved in hot water compared to cold or room temperature water.

Boiling a mixture of sugar and water does more than simply allow larger volumes of sucrose to dissolve in water. As the temperature of the sugar solution rises, water evaporates and leaves behind the sugar in its molten form. This creates a very concentrated sugar solution. Different sugar concentrations correspond to different types of candies (Table 1). In the case of hard candy, confectioners and professional candy-makers typically bring the boiling sugar solution to about 150°C (302°F) before removing it from the heat.

Table 1: Stages of Sugar Cooking (Adapted from Crafty Baking.)

Stage Temp (°C/°F) Sugar conc. Candy examples
Thread 110-112/230-234 80% Sugar syrup, fruit liqueur
Soft ball 112-116/234-241 85% Fudge, pralines
Firm ball 118-120/244-248 87% Caramel candies
Hard ball 121-130/250-266 90% Nougat, toffee, rock candy
Soft crack 132-143/270-289 95% Taffy, butterscotch
Hard crack 146-154/295-309 99% Brittles, hard candy/lollipop
Clear liquid 160/320 100%
Brown liquid 170/338 100% Liquid caramel
Burnt sugar 177/351 100% Oops…

At this point, the sucrose has been concentrated to such a degree that it is considered supersaturated. Supersaturated solutions are unstable, in the sense that any type of agitation, such as stirring or bumping, will trigger sugar crystallization: sucrose molecules will transition out of the molten liquid solution into a crystalline, solid state [2]. Think of sucrose molecules as Legos; crystallization is the process of these molecules locking together into a solid structure. It may not seem like it, but crystallization is a big no-no in hard candies.

In broad terms, candies are categorized as crystalline or non-crystalline. Crystalline candies, such as fondants, fudges, and marshmallows, are soft, pliable, and creamy thanks to their sucrose crystal structures. Conversely, non-crystalline candies are firmer and include toffees, caramel candies, brittles, and hard candies. Unwanted crystals in these candies create a grainy, even gritty, candy texture. Hindering the crystallization process is crucial for making a successful batch of hard candies.

This is where corn syrup, another key candy ingredient, plays an important role. Corn syrup consists primarily of starch, which is nothing more than a string of sugar (glucose) molecules linked together. When heated, the starch breaks apart into its glucose components. These glucose molecules are smaller than sucrose and can impair crystallization by coming between the sucrose molecules, ultimately interfering with crystal formation [2]. In some recipes, invert sugar or honey may be added in lieu of corn syrup. Invert sugar and honey are both mixtures of glucose and fructose, which impede sucrose crystallization the same way as corn syrup.

During the final stages of candy-making, the sugar solution is poured onto a cooling table. As it cools, it takes on a more solid, plastic-like mass that is still very pliable. Flavors and dyes are added at this stage. Sometimes an acid, such as citric acid, is also added. These acids further prevent sucrose crystallization by hydrolyzing sucrose molecules into their basic components: glucose and fructose. The sugary mass is then aerated, often by rolling, pulling, or folding, so that it cools down quickly and becomes more solid. This is the creative stage in which the candy-maker kneads, rolls, molds, and cuts the candy into its final shape.

Hard candy is ready to eat once it cools down to and hardens at room temperature. At its completed stage, hard candy is similar to glass: it’s an amorphous solid that is shiny, rigid yet fragile, and sometimes transparent.

Who knew such simple, little candies could be so complex?

References cited

  1. Sucrose, International Chemical Safety Card 1507, Geneva: International Programme on Chemical Safety, November 2003.
  2. Ouiazzane, S., Messnaoui, B., Abderafi, S., Wouters, J., Bounahmidi, T. Modeling of sucrose crystallization kinetics: The influence of glucose and fructose. Journal of Crystal Growth, 2008; 310: 3498–3503.

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

Banana

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Photo Credit: Thomas Abbs (tabsinthe/Flickr)

Photo Credit: Thomas Abbs (tabsinthe/Flickr)

Among fruits, bananas enjoy huge popularity. The Market and Policy Analyses of Raw Materials, Horticulture and Tropical (RAMHOT) Products Team even reported that within the U.S. in 2012, per capita banana consumption was calculated at 13.8kg [1]. The humble banana even reigns as the main fruit in international trade, according to the Food and Agriculture Organization of the United Nations (FAO) [2]. But as a flavor? Banana candies are often the last flavor left in the bowl.

The disparity between the pleasant and sickening feelings which banana flavoring can invoke lies in the intricacy of banana flavor chemistry. The fruit itself contains a mixture of volatile compounds that are responsible for its characteristic flavor. Up to 42 molecules have been identified to contribute to the aromatic profile of bananas [2]. Each of these molecules, when isolated, has been reported to give off their own unique scent [2,3]. Most of the scents are described as floral, sweet, and generally fruity, which are expected when analyzing aroma compounds derived from bananas. However, there are a few volatile compounds that emit odors not usually associated with bananas. For instance, eugenol, one of the significantly abundant aromatic compounds found in bananas, smells spicy, like cinnamon [2,3].

Of all the volatile compounds detected in bananas and analyzed, one stands out as the banana flavor molecule: isoamyl acetate. With a scent often described as “over-ripe bananas”, pure solutions of isoamyl acetate are sold as “banana oil”. Isoamyl acetate is widely used as a flavorant to confer that over-ripe banana flavor in foods. Yet, as many can attest, pure “banana flavor” tastes awful, nothing like the actual fruit. Despite its presence in the banana itself, how does the banana-flavor molecule miss the mark so badly in candy?

Isoamyl Acetate

Chemical complexity is one explanation, as there are 30-40 other aroma compounds that contribute to natural banana flavor. Additionally, in a ripe banana, although isoamyl acetate is one of the key molecules in banana aromatics, it is found in small amounts compared to the other volatile compounds [2,3]. Yet, even though isoamyl acetate is not the most abundant compound in the aromatic profile of bananas, it is a heady flavor on its own: this molecule can be tasted in concentrations as low as 2 parts per million [4].

So, maybe a banana-flavored Laffy Taffy contains a higher concentration of isoamyl acetate than an actual banana. Until scientists and flavor chemists figure out how to make banana-flavored foods actually taste like bananas, at least the yellow Laffy Taffy has its small but dedicated fan base.

References cited

  1. Banana Market Review and Banana Statistics 2012-2013. (2014). Retrieved October 2, 2014.
  2. Jordán MJ, Tandon K, Shaw PE, Goodner KL. Aromatic profile of aqueous banana essence and banana fruit by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). J Agric Food Chem. Oct 2001;49(10):4813-7.
  3. Pino J, Febles Y. Odour-active compounds in banana fruit cv. Giant Cavendish. Food Chemistry. Mar 2013;141(2013):795-801.
  4. Bilbrey, J. (2014, July 30). Isoamyl acetate. Retrieved September 28, 2014.

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