The Chemistry of Smell

Rui M.

Life in NYC is not easy. One of the biggest problems is the food. Of course, I can eat out a few times since the city is filled with wonderful restaurants. But as living becomes more and more expensive, I have to force myself to eat at home. Cooking is a real challenge, especially since my spice tolerance is terribly low; I can’t eat food with a strong smell (I think this is a good explanation for why I’m a cheese and garlic hater, but people still think of me as a “weirdo”). My oldest and probably only friend, D, never understood my own personal preferences about food. After she cooked for me this afternoon, my whole apartment ended up with some interesting smells – the smell of garlic and camembert. Of course I know she did it on purpose!

Why do camembert and garlic have such mysterious smells? I found a blog that gave me the perfect answer to my question, although it was sometimes so academic that I couldn’t understand a word. The blogger suggested that camembert has such a strong smell because of the wide range of compounds that are produced during the ripening process. The chemicals with scary names include dactyl, which makes the cheese buttery, methanol, which gives the cheese the smell of boiled potatoes, methanethiol (the smell of cabbage), and 1-octen-3-one (the smell of mushrooms). I guess I can stand the smell of each chemical in isolation, but after they are mixed up, all I want to do is stay as far away as I can.

However, that’s not the whole story about camembert.  There is another compound that makes it even more unbearable: ammonia. This compound is produced by the deamination of amino acids and its amount increases as the camembert becomes ripe. So as time passes, the smell may become unexpectedly strong and then no one can bear it–not only me.

Similar to camembert, garlic has its own chemical contributors that lead to its unique smell, including diallyl disulfide, allyl methyl sulfide, allyl mercaptan, and methyl disulfide. These compounds are absorbed and passed into the bloodstream, and then passed on to other organs. The compounds travel through the body and are eventually excreted though the skin and breath. These compounds are what cause  “garlic breath”. Allicin, on the other hand, is a chemical that is responsible for the smell of chopped garlic. This compound is formed when the garlic clove is damaged and the enzymes break down alliin, which eventually becomes allicin.

Although I hate the smell of garlic, I understand that many people love it. So I have  good news for people who love garlic dishes but worry about garlic breath: there are plenty of foods that can reduce garlic breath. For example, milk, apples, parsley, and mint can all help. However, the mechanism behind this reduction still remains unclear. Some researchers think that chlorophyll, which is usually found in vegetables, is the main contributor to this reduction effect. Other researchers do not agree with this hypothesis. They suggest that an enzymatic action is the main reason, since enzymes break down most of the organosulfur compounds. Hope our future chemists can solve this problem one day.

Obviously, the smell of camembert and garlic, no matter whether I like it or not, is all about chemistry! So choosing food is like choosing the correct chemicals:  each individual has his or her own preference. Some people prefer the strong smell of onions while others prefer the faint aroma of apples. Chemicals are the contributors! Chemistry is found everywhere in the world, but most people simply ignore it (OK, I have to admit that I’m one of them). After I read the chemist’s blog, I was attracted to this study of compounds. I decided to apply to a college and study chemistry from now on. Fantastic decision, right?

Friends, it’s time for dinner. D is mad at me right now. Hopefully, I’ll post more interesting facts about chemistry later. See you next week!


The Chemistry of Camembert

What Compounds Cause Garlic Breath? – The Chemistry of Garlic

Chemistry Matters Symposium

Chemistry Matters Symposium

Rui Ma

Why chemistry matters? Because it is the foundation of life and development. We witness thousands of chemical reactions every day, from a small cup of coffee to the components of the atmosphere. However, while a few of people can truly appreciate the importance of each molecular interaction and how it affects our lives, most of us just ignore it. The Chemistry Matters Symposium was a great opportunity for us to learn some facts about chemistry, beyond the textbooks. During the symposium, I was impressed by the information and insightfulness of each presentation, and I chose three of them as my personal top presentations.

In my opinion, the top presentation was Chocolate—the New Health Food, or Is It?, presented by Catherine U.

This presentation was primarily about the reasons why chocolate is simultaneously considered to be both beneficial and harmful. It is healthy because it contains anandamide, a chemical produced by the brain which blocks out depression. Also, chocolate contains polyphenols, which belong to a group of antioxidants that could protect cells against free radical molecules. Flavanols, a group of chemicals present in cocoa, could increase nitric oxide levels in blood and thus improve heart health. At the same time, however, chocolate can be harmful because of it contains saturated fats, which result in high caloric content. Also, the chocolate-making process, especially roasting and fermenting, can significantly  decrease the amount of antioxidants found in the product.

Catherine’s presentation was very organized. She presented the beneficial and harmful aspects separately and gave her own suggestions about how we should consume chocolate. She provided the audience with many details about the chemicals present in chocolate and how they affect the human body. By using this information, she successfully made a connection between chemistry and our lives. Catherine was also familiar with her topic and this familiarity lead to confidence. She had good eye contact and appropriate body language, so her presentation was relaxing and engaging. Overall, Catherine’s professional and well-organized information made her one of the best presenters in the symposium.

My second choice for top presentation was The Sweet Science of Candy Making, presented by Hannah H.

This presentation was about how intermolecular forces affect the textures of candies. Hannah divided her presentation into three parts: rock candy, small crystals of fudge, and candy with no crystals. The crystallization process of rock candy can be explained by Le Chatelier’s principle: as the temperature increases, the energy decreases. Since the breakup of the bond absorbs energy, the sucrose molecules dissolve in the solution and form crystals. Candy with small crystals, like fudge, requires stirring to push sucrose molecules into each other, thus forming small crystal seeds. For candy without crystals, the cooling process must be rapid so that crystals have no time to form.

Hannah’s presentation was as well-organized as Catherine’s. She divided her presentation into three smaller sections, which helped the audience gain a better understanding of each of the subtopics. Her language was at an appropriate level so even people who were not familiar with chemistry could understand her presentation; this is something that most of the presenters failed to do. Moreover, she successfully related chemistry to the candy-making industry.

My third place presentation was Natural, Braided, Bleached, Colored, Straight, and Curly Hair, presented by Tyler D.

Tyler’s presentation was focused on hair products and how they affect our hair, especially hair dyes. He divided hair dyes into three subcategories: temporary, semi-permanent, and permanent. In temporary hair dyes, the color pigments are large so they do not penetrate the hair’s cuticle layer. The semi-permanent hair dyes affect the hair shaft but do not remove the hair pigments, whereas permanent hair dyes remove the hair pigments by using hydrogen peroxide, and then introduce the new color pigment into the hair through the use of p-aminophenol.

Tyler’s presentation had many subunits, so he could only focus on a few of them. I think he did a great job balancing each topic. He did not give too many details about all of the available hair products; instead, he mainly focused on hair dyes so the audience could follow along more easily. Since his topic was not an easy one, he used visual aids (pictures) to make his information more straightforward and interesting. He had good eye contact and clear language, and although sometimes he seemed to be nervous, his overall presentation was professional and impressive.

All of these presenters not only shared with me so many interesting facts about chemistry, they  also taught me how to become a better presenter. Proper eye contact and body language can make the presentation relaxing and engaging; but the most important skill is to use an appropriate level of language: that is what defines a good presentation. These presenters successfully simplified the information they had and gave clear explanations about each of the unfamiliar concepts, instead of overwhelming the audience with difficult chemicals and reactions. Even someone who does not know chemistry could follow their presentations, so everyone can truly understand that chemistry does matter in our lives.

Truth About Chemical-Free Products

Rui Ma

“Chemical-free” products become more and more popular recently since consumers are increasingly aware of the bad consequences caused by harsh chemicals. However, I think “chemical-free” is actually a misleading concept because everything that exists on the Earth is made up of chemical compounds of different elements. So I guess the marketers do not mean that their products contain 0% of chemicals, what they are trying to convey with this label is that their products are natural, organic and without any harmful chemicals.

When I searched for chemical-free products on the internet, a shampoo caught my eyes immediately: Aloe Vera by Jason Natural. Many online sellers claimed it is a shampoo which free of chemicals. On the front side of the product, it is labeled as “pure natural shampoo”. I have no idea whether it is a natural and organic shampoo or not, what I know is that the producers and sellers are giving wrong concept to the consumers. On the back side of the bottle of shampoo, the producer gives the consumers a list of “all-natural” ingredients: Aloe Barbadensis leaf juice, aqua (water), glycerin, sodium chloride, citric acid… (1) All these ingredients are made up of chemical compounds, so how could a person claim it as “free of chemicals”?

A simple example which can break this unreal label is banana. Since a banana is all-natural, so people may expect that it has to be “chemical-free”. But in reality, a banana is filled with chemicals: water, sugars, glutamic acid, aspartic acid, histidine, leucine, oleic acid, valine, alanine, E460,E462 and other tons of unfamiliar ingredients.(2) It is interesting to imagine that if someone just heard about an unnamed food which contains phylloquinone, ethyl butanoate and isoleucine, would he or she still eat it without hesitation? Not really. I guess that person will refuse to eat that food despite the fact it is just a banana.

Similarly, consumers would feel panic about an “unnatural” shampoo with tons of strange chemicals in it, that it is why so many producers label their products in a misleading way. But since the label is inappropriate,the producers may choose a better one to convey the consumers. To be more specific, SLS (Sodium Lauryl Sulfate) is a typical chemical which is considered to be unhealthy and harmful in shampoo companies, so if their products is truly free of SLS, all they need to do is label it as “SLS-free” rather than “chemical-free”. The producers must to be more specific in order to become more convincible about their products.

As a consumer, I believe that it would be wiser to gain necessary information of a product and fundamental chemistry knowledges than to fully trust a “all-natural” label. Because there is nothing that is truly free of chemicals and not all man-made chemicals are harmful to human body. It is important for us to be more aware of what we are consuming and never become negative about chemicals which are necessary for human needs.



(2)Novak, Matt. 2014. All Natural Bananas Are Filled With Chemicals.