Author: yuki0711

The Magic of Bread

Bread is a good thing. I regard it as the necessity on the dinner table and one of the indispensable developments and creations in the food industry. Bread can be eaten alone as breakfast or combined to other dishes to balance the flavor. As a big fan of bread, I think it may be a good idea to talk about the process of making bread and its charm in such a tender and beautiful spring day.

Bread-making contains four simple steps, but the chemistry behind it looks more complex than the straightforward recipe. Firstly, mix three of the four different ingredients: flour, water, and salt. This dough is the foundation of the bread. Then, knead the dough. The starch in flour will be converted into glucose, which acts as the food for yeast. The third step is to add the yeast and wait for the fermentation. Although simple and boring, kneading and fermentation are essential in bread-making because they determine the taste and how puffy your final product is. Finally, bake the well-fermented bread into the oven and wait for the magic, brown, yummy bread!

One reason I like bread is that it smells tasty. The aroma spreads out through the oven and stimulates my taste buds. I just cannot wait to have my wonderful accomplishment! But, wait a minute, where does the aroma come from…hmm, an interesting question to think about. There are three sources that where the aroma comes from: ingredients, fermentation, and baking. It is obvious that the ingredients you use in the bread can determine its smell; for example, you will add chocolates into the bread if you want to make chocolate bread, and chocolates bring the smell of themselves into the bread. However, this in only a minor contributor compared to the later chemicals. During the fermentation, yeast uses sugars created by the enzyme to produces chemical compounds, and the aroma is the byproduct of these productions. Maillard reactions happened in the baking process. It has two classes, between sugars and amino acids, and sugar caramelisation reaction. Both reactions create the brown color in the crust and produce the aroma and taste of the bread.

It is clear to learn about bread by the combination of bread-making process and its aromatic sources. Although each step in the process is important, the one that contributes the most to the smell is the baking process. Not surprisingly, crust and crumb contain different chemicals. For the crust, maltol and isomaltol are derived from the caramelisation reaction of sugar. They produce the malty aromas, which corresponds to their names. Another significant chemical called 2-acetyl-1-pyrroline (2AP) is formed in the Maillard reaction. It has a roasted and cracker-like smell. A higher level of yeast in the bread results in more 2AP. These compounds create not only the aroma but the brown coloration as well. On the other hand, crumb has lower levels of compounds I mentioned above. Furthermore, it has its own aroma sources and, strangely enough, they actually mimic the smell of other stuff. In the Maillard reaction, (E)-2-nonenal and (E,Z)-2,6-nonadienal have the smell of cucumber. (E)-2-nonenal is related to the odor of human as age increases. 2,3-butanedione, which is also known as diacetyl, creates the scent of potato. Even though all those compounds have their weird smell alone, the combination of them produces the smell of bread. Isn’t this cool! These compounds are the major but small parts of all the smell resources. The final aroma consists of a large collection of all chemical compounds formed in the bread. Overall, different types of bread have various compounds and create their unique aromas.

Food is for the enjoyment of its taste and appearance, but more importantly, food supports our health. A lot of people like bread and it is a good thing to me at least. However, we need to control and pay attention to the amount we take in per day. Fermentation is good for health but manufacturers put too much sugar and oil to ensure the flavor. Eating too much bread can cause obesity or even cardiovascular diseases. Hope you enjoy the yummy food and also, take care of yourself~


Baking Bread: The Chemistry of Bread-Making

Aroma Chemistry – The Smell of Freshly-Baked Bread


Chemistry Matters Symposium

Chem 131 held a Chemistry Matters Symposium last week during the lab session. We presented about various chemistry related matters or phenomenon in daily life and shared what we learned from the reading. The symposium was much more efficient and entertaining than study all those materials by oneself. Other than learning new stuff in chemistry, I also experienced different types and styles of presentations. My peers’ speeches kind of reflected overall how I did in my presentation. I started to think about how I can improve my presenting skills by listening to others.

Among all the eleven speakers, the top one in my mind belongs to Monica. Her topic was the sweet science of candy making. The first step of making candy is to dissolve the sugar in the water. In a sugar crystal, the sucrose molecules attract each other by intermolecular forces. When the sugar is added into the water, water molecules will bond sucrose molecules and pull them away from each other, so the sugar crystal starts to dissolve. The water, however, can only dissolve a certain amount of sugar and becomes saturated. Actually, at the start of adding sugar into the water, some sucrose molecules also crystallize because they constantly move in the solution, while others are attracted by water molecules. At this time, the speed of dissolving is faster than crystallizing, so it is hard to see any precipitation. As more sugar is added into the water, crystallization speeds up and dissolving slows down, and they finally reach the same speed. This is when saturation happens. If the amount of sugar excesses the saturated point, sugar cannot dissolve into the water anymore, but reaches the dynamic equilibrium with the solution. Water can dissolve more sugar at a high temperature by increasing the dissolving speed. When the water cools down, the sugar crystal forms to generate energy. Thus, rock candy is completed. Monica did a great job explaining the whole process. She walked us through principals clearly and humorously. She talked in a proper volume and speed with gestures. She kept having eye contacts with audiences. She came prepared and spoke fluently. She also did the experiment by herself, so she had a better understanding of how the process worked and what each step looked like. I did not feel that she was nervous. Her way of talking was more like having conversations with friends than giving a speech. I enjoyed listening to her and learned how to make candies.

Another great presentation was about coffee. Coffee is well known for awakening and bringing energy. But how can coffee be so useful? Coffee contains caffeine, the chemical that can alert the brain. After people drink coffee, the caffeine prevents adenosine, which can cause the drowsiness, to get in touch with adenosine receptor. People can stay awake for hours after drinking coffee. Besides alerting the brain, coffee is beneficial to health. Coffee can help people stay away from alcoholism and release stress. Although it is hard to believe, coffee can also protect teeth by preventing the growth bacteria. The deepest impression I had for this speaker was her professional. She wore formal clothes that showed respect to the presentation. Her power point was neat and organized that I could immediately get her outline and emphases. There were only phrases on the slides instead of sentences that I could focus on her talking while also know the main concepts. She pointed to the words on hand so I always followed her thoughts. She spoke calmly and reasonably that made her points easy to understand. The only thing she might improve was to add more pictures to the slides so that people could be more interested in and focused on the topic.

I was also impressed by the talk about chocolate by Lauren. I like her idea to reorganize the contents by her own thoughts and walked us through her reasoning. She divided the most important chemicals in chocolate into two parts, ones that made you feel good and ones that benefited your health. For the first category, chemicals like caffeine and theobromine can make people alert. Other chemicals can stimulate the brain by anandamide to make people feel happy and excited. For the second part, polyphenols, which belongs to antioxidants, is good at preventing Alzheimer’s disease, heart disease, and cancer. Chocolate can prevent the teeth decay as well. However, all these benefits are related to dark chocolates and require a high amount of cocoa. Many chocolates in the markets contain little cocoa and a lot of sugar to improve the taste. Lauren presented with the passion because she loved chocolates. Her passion could influence audiences and engage them more to her topic. She spoke with confidence that her voice was bright and firm. I like the feeling of hearing a story from her talk because she combined the knowledge with our daily lives. She also put some pictures on slides that helped me know the structures of those chemicals.

I like hearing other people presenting. Some people are really good at giving speeches, and I am attracted to them and never feel bored. I can always reflect on myself that if I show the same strengths as others or if I make the same mistakes that make audiences uncomfortable. The most important quality is to be confident and passionate. The speaker’s emotion will deliver to audiences and engage them in the talk. Eye contact is also important and can avoid losing their attention. Most essentially, well prepared before the talk. People can tell if you practice or not. Finally, enjoy the show!


I need chemical-free…or do I?

Every time I walk into a market, I prefer products that are labeled “natural, organic, or chemical free”. In our tuition, products that are more related to nature should be healthier and bring less harm to our body than others. After all, nature won’t hurt us. We would like to see the ones we use are derived from nature, especially for things like make-up, nail polish, and shampoo that contains toxic chemicals. However, there is an important notation that matters on earth are all made by chemicals, even the air we breathe and water we drink are composed by H and O, pure chemicals. That means, the nature, we love and admire, is about chemistry. Chemical-free is an impossible goal to meet, well, at least by technology nowadays.

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Before we discuss why chemical-free is inappropriate, let us focus on a daily product, NaturOil Soap Nut Shampoo. When you first see it, I guess you cannot stop your impulse to buy it immediately. It has nature in its name and is labeled both organic and chemical-free. What are we waiting for!! Hang on a second. Is it really chemical-free? Let’s check the ingredients first. The most obvious three are botanical glycerin, citric acid, and lauryl glucoside. We can easily recognize them as chemicals just from names. Next, this shampoo has several extracts from different leaves and seed oil. Although they look like really natural, the nature is made by chemistry. At last, this product is full of chemicals.

Based on the ingredients above, it is apparent that this NaturOil Soap Nut shampoo is not chemical-free. Furthermore, nothing on the earth is chemical-free, even the human body contains a lot of carbon. Then why do sellers place “chemical-free” on the shampoo? In my opinion, the “chemical” here is not referred to all chemicals, but to those harmful to human body. For example, as we know, the use of silicon in shampoo can make hair smooth and shiny. However, this does not mean your hair is really healthy. The smooth and shine is the fake phenomenon that caused by silicon’s chemical property. After using silicon shampoo for a long time, your hair will become thin and easily broken. Furthermore, large amount of silicon and sodium laureth sulphate, a common component in shampoo, increases the possibility of causing cancer. The use of “chemical-free” here is to clarify that this shampoo does not contain toxic chemicals, like silicon and SLS, which are harmful to your hair and body.

Based on the science aspect and in order to make more sense, changing “chemical-free” into “toxin free” may be a good choice for this shampoo. This can be more accurate than chemical-free and provide safe products for customers.

Chemical-free is inappropriate for everything around us. Chemistry is the foundation of our life. Although it sounds like unnatural and artificial, we should regard it with scientific mind. Chemical itself is not toxic, but we should choose correct chemicals for achieving certain task. Moreover, the usage and proportion of different chemicals in products are also significant. Excessive dosage can even turn medicine into poison. Thus, it is not necessary for us to have everything chemical-free. The only thing we need is to avoid excess harmful chemicals.

4 Chemical Free Shampoo Brands You Should Try