All posts by shelly01pd2014

Fermented Food

Everyday at dinner, my mother would bring Kimchi to the table. I myself am not a big fan of the taste of Kimchi, but in my opinion, my mother, like all Koreans, might be. During the SARS outbreak 11 years ago, my uncle convinced me to eat Kimchi by telling me that the reason Korea was not affected by SARS was that all Koreans ate Kimchi. 11 years later, I am still asking myself what is so special about this fermented vegetable that Koreans and a few foreigners are crazy about. So I came up with the research question for this blog post: What are the positive and negative effects of consuming fermented food, and what is the chemistry behind them?

Kimchi is not the only type of food that has been through fermentation. Our favorites such as cheese, yoghurt, and smoked salmon have also been through this process. So, to begin, what is the definition of fermented food? According to Peter Sahlin at Lund Institute of Technology, fermented food is any foods influenced by lactic acid producing microorganisms. Similarly, fermentation was categorized by the World Health Organization as a “technique for preparation/storage of food.” This is because in the developing countries, one tenth of the children below the age of five die because of dehydration because of diarrhoea caused by unhygienic conditions. In this case, lactic acid fermentation has been discovered to “reduce the risk of having pathogenic microorganisms grow in the food.” (Sahlin, 1999)

Fermentation of foods has been an ancient traditional practice. Tiberius the Roman emperor always had a barrel of sauerkraut when he traveled to the Middle East because Romans knew of the effects of lactic acid that included protection from intestine infections. (Schachter, R. ) Over the years, fermented foods have continued to be known to create beneficial probiotics to our guts. Having healthier guts lead to healthier digestion, which means having better absorption of nutrients, vitamins and minerals, improving overall health. In addition, fermented foods have helped in relief from lactose intolerance, prevention of colon cancer and  prevention of reoccurrence of bowel disease. (Sisson, M., n.d.)

The beneficial effects of fermented food are caused by the lactic acid bacteria that form during fermentation which increases the acidity of the food (decrease the pH) as the bacteria convert energy from sugars and starches into lactic acid. (Erickson, Fayet, Kakumanu & Davis) Lactic acid bacteria, according to Sally Fellon, writer of Nourishing Traditions are ‘beneficial organisms that produce numerous helpful enzymes as well as antibiotic and an anti-carcinogenic substances.” (Pickl-It., n.d.) From what I have previously learned, acids such as lemon are able to kill harmful bacteria. When I connect this fact to my research, I could most likely conclude that when fermenting food, the food is not only stored at a state where harmful bacteria are not able to cultivate, but also the production of beneficial enzymes are not interfered, hence resulting in the beneficial effects of fermented food, such as improvement in digestion.

Figure 1: Lactic Acid Structure

However, when fermented food are over consumed, there can be negative health impacts.

Even though aldehydes are not toxic substances, if one encounters a high toxic level of aldehydes through foods such as kombucha tea, some pickles, wine and beer, one’s health may be damaged. Aldehydes are a type of organic compound produced by fermenting organisms, or oxidation of alcohols. They commonly contaminate cigarette and other smoke such as smog, vehicle and factory exhaust, synthetic fragrances, and others. (Schachter, R., n.d.) The human body has enzymes that are able to convert the aldehydes into a less-harmful substance, but when there is a high level of aldehydes, the aldehydes can become toxic and travel to the brain, causing neurological diseases. Another harmful effect of aldehydes is that it damages red blood cell membranes. What this  means is that red blood cells will become “less flexible in passing through tiny capillaries, altering hemoglobin” (oxygen transporter in RBC). In other words, there will be less oxygen available to the cells in the body, especially the brain. (Pierini, C., ASCP, C., & CNC. n.d.)

Figure 2: Aldehyde Structure
Figure 2: Aldehyde Structure

Despite that my sources suggest both negative and positive health implications of fermented food, they are not clear about the specific diseases that can be caused by the negative impacts of fermented food, but only clear about the specific diseases that can be prevented by the positive impacts. From this, I may be able to assume that the positive consequences of eating fermented food may be greater than the negative consequences, and if I would like to avoid the negative consequences, I may need to avoid certain types, such as alcohol, although this may not be a problem as I am not an alcohol consumer.

After learning about the effects of fermented foods, I realized that it was no coincidence that my mother had intestinal problems. I learned that all this time, when my mother was bringing Kimchi to dinner table, she was eating the fermented vegetable for her health rather than for the taste.

Figure 3: Kimchi


1. Erickson, L., Fayet, E., Kakumanu, B., & Davis, L. (n.d.). Retrieved from Files/CH 5 – Lactic Acid Fermentation.pdf

2. Pickl-It: What is lactic acid?. (n.d.). Pickl-It. Retrieved September 15, 2013, from

3. Pierini, C., (ASCP), C., & CNC. (n.d.). A Health-Destroying Toxin We Can’t Avoid And Must Detoxify. Vitamin                         Research Products. Retrieved September 16, 2013, from http://


4. Sahlin, P. (1999). Fermentation as a method of food processing. Retrieved from:

5. Schachter, R. (n.d.). Risks and Benefits of Fermented Foods Consumption | Wake Up World. Wake Up World.

Retrieved September 14, 2013, from

benefits- of-fermented-foods-consumption/

6. Sisson, M. (n.d.). The Health Benefits of Fermented Foods | Mark’s Daily Apple. Mark’s Daily Apple. Retrieved                     September 14, 2013, from


7. Aldehydes and Ketones. (n.d.). Boundless. Retrieved September 15, 2013, from–2/functional-group-names-


8. Healthy Kimchi Burritos | Hungry Girl in Korea. (n.d.). Hungry Girl in Korea | The blog about healthy cooking and baking in Korea. Retrieved September 16, 2013, from

9. Helmenstine, A. M., & Ph.D.. (n.d.). Lactic Acid Chemical Structure. Chemistry – Chemistry Projects, Homework Help, Periodic Table. Retrieved September 16, 2013, from—L/Lactic-Acid.htm

Plastic- Why “Purchase”?

A few days ago, while I was at Cityshop waiting for the cashier to finish up her job, I was asked whether or not I wanted a plastic bag. I nodded as if it was an obvious answer, when the cashier added, “You will need to pay extra.” Since a few years ago, additional charge has been added to almost all plastic bags in China to reduce the use of plastic and promote alternative ways to transport groceries. Why? I vaguely knew that plastic took a long time to erode so when they are dumped into the ocean or buried in the soil, it caused harm to marine life, etc.  So I decided to do further research on the chemistry of plastic.

There are many properties of plastics. According to the official website of the Nobel Prize, the Greek word of plastic means “to mold”. This fits the properties of plastic perfectly as all plastics, during production, are “soft and moldable”, allowing productions such as carriers of vaccine. (Nobel Media AB, 2007) Additionally, plastics have low density and electrical conductivity, transparency and toughness. (Rodriguez)

So what are plastics? They are synthesized materials manufactured in factories. They are made up of small organic molecules that contain carbon compounds from petroleum and natural gas, and even from fibers, corn, or banana peels. These molecules are monomers that combine with other monomers and form polymers, long molecule chains. What is interesting about polymers is that they in a way imitate nature, for example DNA that carries genetic information. (Nobel Media AB, 2007) This covalent bond can be shown by the two types of chemical compositions of plastic: linear Carbon-chain and Heterochain polymers. Carbon-chain has only linear Carbon atoms in the backbone chain, while the latter compounds contain carbon, oxygen, nitrogen or sulfur atoms in the backbone chains. (Rodriguez)

Carbon-chain Polymers
Carbon-chain Polymers

(Picture 1: Examples of Carbon Chain)


(Picture 2: Example of Heterochain-polymers)

Now that we know the properties and structures of plastic, we need to find out more on how they are made through the process of polymerization. As mentioned earlier, plastics are made up of carbon molecules, or the ethylene molecule (C2H4). Nobel Media also mentions that Polymerization begins by joining monomers into a polymer chain through a catalyst (results in chemical reaction without any permanent chemical change). The resulting polymers are called resin, and or polyethylene resin in the case of polymerization of ethylene. Resins are then purchased by factories, and added into different additives to form the properties of intended product, for example plastic bags that I “purchased” at Cityshop, fibers for sweater, etc. (Nobel Media AB, 2007)

There are two types of plastics, Thermoplastics and Thermosets. According to Nobel Media, 80% of plastics produced are thermoplastics and 70% most widely used. The reason would be that thermoplastics can be reshaped, melted, and easy to recycle due to its long and linear polymer chains that are weakly bonded and easily broken. Thermosets on the other hand cannot be reshaped due to their cross-linked structure and strong chemical bonds that prevent reshaping of the plastics. This is hard to recycle, so they are crushed into a fine powder to use as fillers in reinforced thermosets. (Nobel Media AB, 2007)

After all the information, I have learned that the plastic bag I “purchased” at Cityshop was a type of thermoplastics, meaning it can easily be recycled and reformed into another product. However, if that is where the story ends, consumers like me should not even need to pay for the widely used plastic bags. Therefore, I did some more research on the effects of plastics in the environment that might have caused the discouragement of using plastic bags.

It turned out that plastic contributed to environmental issues in a lot of ways. First, according to Nobel Media, the production of plastics involved excessive energy and water use. What this means is that the production of plastic itself contributes to climate change affecting both humans in depletion of natural resources and the extinction of wildlife, a major global issue today. Secondly, according to Chemistry Daily, plastic cannot be broken down completely, even though some biodegradable plastics can be mixed with starch in order to degrade more easily. When the carbon that is “locked up” in the plastics is released into the atmosphere, the greenhouse gas emission once again contributes to global warming. In addition to global warming, the increasing production of plastic will also increase in the existence of plastic and its harmful consequences. In addition, even if plastics decay, some produce acidic gases when they decay. This results in the building up of a sealed environment. (An environment that does not “connect to the external environment and runs on the closed loop.” (Biksa) ) A few days ago as I was searching through a topic for Economics IA, I found an article related to the effect of plastic use on marine life. Dr Boxall said in an interview for BBC, “These plastic particles are like sponges, they’re a bit like magnets for other contaminants, things like Tributyltin, the anti-fouling material. The tiny plastic particles absorb these materials and effectively become quite toxic.” This implies that excessive use of plastic not only affects humans directly, but also indirectly by affecting marine lives that humans consume. In the long term, global warming will no longer be the only major issue in the world, but also marine life pollution.

Plastic in Sea
Plastic in Sea

(Picture 3: Tiny pieces of Plastic found in the sea)

For many years for humans, we have been taking advantage of the distinct properties such as lightness and durability of plastics. It is true that there were certain benefits that allowed ease in handling daily materials in the short term, however, in the long term, we will have to face the consequences of not looking ahead for the environmental causes. So next time you go to Cityshop, would you “purchase” a plastic bag, or would you just bring along an alternative bag to reduce the use of plastics?


Biksa, E. (n.d.). Simply hydroponics and organics. Retrieved from

Chemistry daily. (2007, April 01). Retrieved from

Lister, T., & Renshaw, J. (2004). Conservation chemistry: An introduction. London: Royal Society of Chemistry Publishing. Retrieved from decay chemistry&source=bl&ots=u9Aa2j0LGm&sig=a_ebfKDR9PX01iXYX8d2YHMalZc&hl=en&sa=X&ei=ti8QUfHJDPKx0QGwxoGoAg&redir_esc=y&hl=zh-CN&sourceid=cndr

Nobel Media AB. (2007, August 28). Retrieved from

Rodriguez, F. (n.d.). Plastic. In Britannica. Retrieved from’

Watts, S. (n.d.). What are long term threats of plastic in our seas? Retrieved from


Rodriguez, F. (n.d.). Plastic. In Britannica. Retrieved from’

Watts, S. (n.d.). What are long term threats of plastic in our seas? Retrieved from