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Garlic

Image Credit: Robert Benner (mullica/Flickr)

Image Credit: Robert Benner (mullica/Flickr)

If you’ve ever made the mistake of devouring three bowls of James Beard’s Garlic Soup a few hours before The Job Interview Of Your Life (I’m not speaking from experience here), you will recognize the frantic moment in which you pray that 1) the handful of mints burning in your mouth have superpower strength, or 2) your interviewers cannot smell, or 3) whoever you’re meeting had four bowls of garlic soup. Ahhh, the allure and woe of garlic. Why do you hate me if I love you so much?

Known for its distinct aroma and taste, Allium sativum – or garlic, as most of us know it – makes dishes sweet and pungent while it turns breaths foul and fetid. But what exactly causes garlic breath? More importantly, how do you get rid of it?

Image Credit: (fiverlocker/Flickr)

“Dear god, what did this guy have for lunch?”  —  Image Credit: (fiverlocker/Flickr)


The Breakdown of Garlic Breath

Garlic contains many sulfur compounds, but the ones most responsible for garlic breath are: diallyl disulfide, allyl methyl disulfide, allyl mercaptan, methyl mercaptan, and allyl methyl sulfide (AMS). The gases released by all of these compounds, except forAMS, originate in the oral cavity when we mechanically crush garlic in our mouths, so brushing your teeth and tongue will reduce the presence of the mouth-originated odors. However, good dental hygiene doesn’t usually entirely get rid of the smell because AMS is what causes unwelcome garlic breath, and this can linger for several hours or even days.

Background Credit: Crispin Semmens (conskeptical/Flickr)

Allyl Methyl Sulfide (AMS), the unwanted pungent houseguest that overstays its welcome. — Background Credit: Crispin Semmens (conskeptical/Flickr)

AMS is a sulfur compound formed inside the body from allyl mercaptan, so instead of originating in the mouth, AMS is produced in the microflora of the gut. The resultant gas quickly evaporates into the bloodstream, which then diffuses to the lungs and infuses each breath of air that leaves our bodies with traces of strong-smelling allyl methyl sulfide. And if that isn’t wonderful enough, the compound is also released through pores of the skin, which is why you may notice a lingering body odor after garlic-heavy meals. Unfortunately, AMS does not get metabolized in your gut and liver like many other molecules that we eat, so it takes much longer for AMS to breakdown – which is why the AMS stays in the body for many hours later. [1]

SOLUTIONS: When brushing your teeth (sadly) isn’t enough

Image Credit: Robert Bertholf (robbertholf/Flickr)

Image Credit: Robert Bertholf (robbertholf/Flickr)

  • EAT THIS: Parsley, Spinach, Mint, Apples, Pears, plus any fruits and veggies that are prone to browning (think avocados, bananas, potatoes, etc.)

    WHY: These foods contain an enzyme called polyphenol oxidase. (The same enzyme is what makes your fruit salad look brown!). When this compound is exposed to oxygen, it reacts in a way that reduces both the odors of the volatile compounds and the formation of more AMS. [2]

Image Credit: A Girl With Tea (agirlwithtea/Flickr)

Image Credit: A Girl With Tea (agirlwithtea/Flickr)

  • DRINK THIS: Green Tea, Coffee,  Ku-Ding-Cha (a bitter-tasting Chinese tea),  Prune Juice

    WHY: These drinks contain a polyphenolic compound called chlorogenic acid, which is another chemical that works to deodorize garlic-derived sulfur compounds on human breath. [2]

Image Credit: (Unsplash/pixabay)

Image Credit: (Unsplash/Pixabay)

  • ALSO DRINK THIS: Lemon juice, Soft Drinks, Beer, Hot Cocoa (and other acidic foods/beverages)

    WHY: When garlic cloves are cut or crushed open, they release an enzyme called alliinase that facilitates the reactions which produce compounds responsible for the smell of garlic. Because these drinks have a pH below 3.6, they quickly destroy alliinase and minimize the formation of garlic volatiles. [2]

Image Credit: Mike Mozart (jeepersmedia/flickr)

Image Credit: Mike Mozart (jeepersmedia/flickr)

  • DRINK THIS INSTEAD OF WATER: Milk!

    WHY: While drinking water works extremely well for reducing garlic breath, milk works even better because of its extra fat, protein, and sugar. Specifically, whole milk is effective in the reduction of the hydrophobic compounds diallyl disulfide and allyl methyl disulfide because of its high fat content. Note that drinking milk during a garlic-heavy meal does a better job of killing garlic breath than drinking milk afterwards, because the milk is able to directly react with the volatile compounds when it is mixed with garlic. [3]

Makes me think garlic ice cream might actually be a genius all-in-one odor-neutralizing dessert!

References Cited:

  1. Suarez, F., Springfield, J., Furne, J., Levitt. M. Differentiation of mouth versus gut as site of origin of odoriferous breath gases after garlic ingestion. Am J Physiol. 1999; 276(2):425–30.[http://ajpgi.physiology.org/content/276/2/G425]

  2. Munch, R., Barringer, S.A. Deodorization of Garlic Breath Volatiles by Food and Food Components. Journal of Food Science. March 2014; 79(4): C536-533.

  1. Hansanugrum, A. Barringer, S.A. Effect of Milk on the Deodorization of Malodorous Breath after Garlic Ingestion. Journal of Food Science. August 2010; 75(6): C549-558.


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.

Read more by Eunice Liu


Coffee Brewing Chemistry: Hot Brew vs. Cold Brew

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