Tag Archive for: flavor chemistry

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.

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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

Ginger

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Photo Credit: Jim Lightfoot (112095551@N02/Flickr)

Photo Credit: Jim Lightfoot (112095551@N02/Flickr)

One rhizome, many tastes. Ginger can be charmingly sweet as candied ginger, gingerbread, and ginger ale. Just as easily, this root can be spiritedly pungent, as in gari (sushi ginger) or unsweetened ginger tea. From sugary snacks to savory dishes, ginger shares similar flavor versatility as cardamom, which should come as no surprise; the two spices are practically cousins. All ginger plants are of the genus Zingiber, which belongs to the same family as cardamom plants, Zingiberaceae [1]. However, the supermarket ginger that most people are familiar with is the knobby, root-like rhizome of Z. officinale, better known as the garden ginger.

Fresh ginger gets its pungency and aroma from the flavor compound, gingerol. Studies have extolled gingerol for its many pharmacological abilities, including antipyretic (fever reducer), analgesic (pain reliever), anti-inflammatory, and antibacterial [2]. The best part? Chemically altering gingerol ends up tweaking ginger’s flavor profile, which helps give ginger its flavor versatility. No laboratories or fancy equipment are needed; as long as there’s a kitchen and a love for ginger-flavored foods, fine-tuning the flavor of ginger is rather straightforward.

Gingerol

Heating a ginger rhizome causes gingerol to undergo a reverse aldol reaction, transforming it to zingerone, a molecule that is completely absent in fresh ginger. Like gingerol, zingerone is responsible for the pungency of cooked ginger, but it also lends a sweeter note to the flavor. For this reason, cooked ginger makes a delightful treat as candied ginger. Zingerone also boasts quite a few pharmacological benefits, notably, its many anti-obesity actions [3]. For instance, zingerone was shown to inhibit obesity-induced inflammation, as well as stimulate the release of catecholamine, a hormone that aids in decreasing fat cells [3].

Zingerone

Drying a piece of ginger triggers a dehydration reaction, changing gingerol to shogaol. Shogaol is twice as spicy as gingerol, which is why dried ginger packs more heat than its fresh counterpart. Additionally, shogaol retains gingerol’s bioactivity, reported to act as an antioxidant, anti-neuroinflammatory, and even memory-enhancing agent [4].

Shogaol

With a multitude of benefits and just as many ways to serve it, there’s really no wrong way to enjoy ginger.

References cited

  1. Zingiber. The Plant List (2010). Version 1. Published on the Internet; (accessed 13 August, 2014).
  2. Young H.-Y, et al. Analgesic and anti-inflammatory activities of [6]-gingerol. Journal of Ethnopharmacology. Jan 2005; 96(2):207-210.
  3. Pulbutr P. et al. Lipolytic Effects of zingerone in adipocytes isolated from normal diet-fed rats and high fat diet-fed rats. International Journal of Pharmacology. Jul 2011; 7(5):29-34.
  4. Moon M, et al. 6-Shogaol, an active constituent of ginger, attenuates neuroinflammation and cognitive deficits in animal models of dementia. Biochemical and Biophysical Research Communications. June 2014; 449(1):8-13.

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

Coffee Brewing Chemistry: Hot Brew vs. Cold Brew

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Chemex. Photo Credit: Nick Webb (nickwebb/Flickr)

Hot or cold, temperature won’t stop many from obtaining their caffeine fix. Depending on the weather and personal preferences, coffee drinkers at home can brew coffee by one of two ways: hot brew or cold brew.

Many are familiar with hot brew coffee. The equipments used for hot brew are widely recognized, and even iconic: the moka pot, French press, Vietnamese coffee filter, and Chemex, to name a few. These equipments, as with all hot brew techniques, involve pouring hot water over a bed of coffee grounds, at a general proportion of 1 oz. coffee to 8 oz. hot water [1]. (That’s 2 level tablespoons per 1 cup of water, on a more home-friendly scale.) The resulting liquid, coffee, is then separated from the grounds and ideally consumed as soon as possible.

Left: Moka pot. Photo Credit: Bill Rice (billrice/Flickr) | Middle: French press/press pot. Photo Credit: Bodum | Right: Vietnamese coffee filter. Photo Credit: Marko Mikkonen (markomikkonen/Flickr)

Cold brew demands more patience. In a Mason jar, French press, or Toddy system, coffee grounds are mixed with room temperature water, and then left to sit for hours—anywhere from three to twenty-four hours—before the solids are filtered out. Cold brew recipes often call for a higher coffee to water ratio: 1 part coffee to 4 parts tepid water, which compared to hot brew, is 2 oz. coffee per 8 oz. water (roughly 4 tablespoons per 1 cup water). Once the grounds are removed, what’s left is black coffee concentrate that is thinned with water or milk before it is served.

Toddy System for cold brew. Photo credit: Toddy

On the surface, the distinctions between the two methods seem self-explanatory. Hot brew quickly produces fragrant java with bite and acidity, whereas cold brew rewards patience with condensed coffee that is smooth and sweet. To begin to understand the flavor profile differences, it helps to first get acquainted with the coffee grounds.

Coffee grounds contain a hodgepodge of volatile and non-volatile components, such as various oils, acids, and other aromatic molecules [2]. Collectively, these compounds that are found in coffee grounds are referred to as “coffee solubles” and significantly contribute to coffee flavor [2]. Brewing is the process of extracting these components from the grounds, so coffee beverages are technically a solution of coffee solubles and water. Given that coffee grounds are used in both of our brewing methods, the principle variables are temperature and time.

Temperature affects the solubility and volatility of the coffee solubles. Relative to brewing, solubility describes the ability of the solubles to dissolve out of the grounds and into the water; volatility refers to their ability to evaporate into the air. Coffee solubles dissolve best at an optimal temperature of 195-205°F [3]. With more coffee solubles extracted, hot brew coffees are described as more full-bodied and flavorful when compared to cold brew. Moreover, due to increased volatility with higher temperatures, the aromatics are more readily released from coffee, giving rise to that beloved scent of freshly-brewed coffee.

On the downside, oxidation and degradation also occur more rapidly at higher temperatures. The oils in coffee solubles can oxidize more quickly at elevated temperatures, causing coffee to taste sour. Acids also degrade, the most notable of which is chlorogenic acid into quinic and caffeic acid, causing coffee to taste bitter [2].

Where cold brew lacks in temperature, it makes up for in time. Coffee solubles have markedly decreased solubility in room temperature water. Increasing the brew time from a few minutes to many hours aims to maximize extraction of the solubles from the grounds. Even over twenty-four hours, not all the coffee solubles will have dissolved; this is why the amount of coffee grounds is doubled, in an effort to make up for the lower extraction rate. In comparison with hot brew, cold brew is sometimes described as tasting “dead” or “flat” due to the lower yield of coffee solubles [3]. Further, decreased volatility prevents aromatics from escaping from coffee as easily, so cold brew is much less perfumed than its hot brew counterpart.

Oxidation and degradation will still occur in cold brew methods, but this happens much more slowly; bitterness and acidity are just about absent in cold brew coffee, especially if it is kept cold. Though, cold brew doesn’t merely taste like hot brew without the bitterness. Fans of the cold brew method have emphasized that cold brews contain a completely different flavor profile that can’t be found with hot brews. Going back to the idea of solubility, not all flavor compounds of coffee solubles are equally soluble. A good majority of the coffee solubles are still able to leach out of the grounds, even in colder water. The compounds that don’t dissolve are the ones often attributed to unfavorable flavors [4]: these stay in the grounds that are subsequently tossed away. Consequently, cold brews take on a much sweeter, floral profile.

To note, brew time does not determine caffeine content, nor does bitterness indicate coffee strength. Caffeine is extracted early in the brewing process, so extending brew time, by either method, would only result in over-extracted coffee [1]. Coffee “strength” is defined as the amount of dissolved coffee solubles per unit of coffee volume [1]. On that train of thought, cold brew certainly produces stronger coffee, given that the brewing process purposely concentrates the coffee solubles. Though, keep in mind that rarely anyone drinks cold brew coffee straight up; many enjoy this smooth drink diluted with milk or water.

Whether you’re an adamant hot brew addict or a die-hard cold brew fanatic, at least coffee drinkers can agree that as long as there’s caffeine, everything’s mellow.

References cited

  1. Brewing—How to Get the Most Out of Your Coffee. Mountain City Coffee Roasters.
  2. Sunarharum W, Williams D, Smyth H. Complexity of coffee flavor: A compositional and sensory perspective. Food Research International. March 2014; 62: 315-325.
  3. Giuliano, Peter. “Why you should stop cold-brewing, and use the Japanese Iced Coffee Method.” Dymaxion.
  4. What Everyone Ought to Know About Iced Coffee & Cold Brew. (2012, June 26). Prima Coffee.

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

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