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 http://fss.kstate.edu/FeaturedContent/CarcassDisposal/PDF 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:// www.vrp.com/digestive-health/a-


4. Sahlin, P. (1999). Fermentation as a method of food processing. Retrieved from: www.eden-foundation.org/project/articles_fermentation_thesis.pdf

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

Retrieved September 14, 2013, from http://wakeup-world.com/2013/04/01/risks-and-

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



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. About.com Chemistry – Chemistry Projects, Homework Help, Periodic Table. Retrieved September 16, 2013, from


One thought on “Fermented Food

  1. Looking on Shelly’s post on lactic acid that is present in foods through fermentation, it reminded me of the time when I learned about cellular respiration in AP Biology. As I could recall, there was also the mention of lactic acid but instead of being in food, it was located in the muscles cells. During AP Biology, the class focused more on aerobic respiration so the creation and effect of lactic acids was not studied thoroughly. I was very interested in how Shelly compared both the positive and negative side of lactic acid in food so I wondered if that also applied to lactic acid in the muscle cells. With a little biological knowledge, it is known that lactic acid creates the soreness that we feel after a workout but there never seems to be any mention of lactic acid doing any good in the body. This leads to my main question: To what extend is lactic acid considered good or considered good?

    In order to evaluated the goodness or badness of lactic acid in the muscle cells, one must first understand the process in which lactic acid is formed in the body, more specifically the muscle cells. The general process of the formation of the acid is when glucose is broken down into pyruvates, and then reduced to form lactic acid.

    In AP Biology, I learned that human skeletal muscles also carry out lactic acid fermentation when the blood cannot supply adequate oxygen to muscles during strenuous exercise. “The pyruvate molecules from glucose metabolism (glycolysis) may be fermented into lactic acid”(Helmenstine) Here is the chemical equation to modify the reaction. 2ATP + 1 Glucose = 2 pyruvate + 4ATP. Note that throughout this entire process all the way to the formation of lactic acid, there is no oxygen involved.

    Fermentation can generate ATP during anaerobic respiration only as long as there is an adequate supple of NAD+ to accept electrons during glycolysis. Without some mechanism to convert NADH to NAD+, glycolysis would shut down. The fermentation is the reaction that regenerates NAD+. It does so by oxidizing NADH to NAD+. As we know, lactic acid in the muscle causes fatigue and burning. The lactic acid continues to build up until the blood can supply the muscles with adequate oxygen to repay the oxygen debt. With normal oxygen levels, the muscle cells will revert to the more efficient aerobic respiration and the lactic acid is converted back to pyruvate in the liver.

    Lets start by examining the positives effects of lactic acid. We all hear the bad things about it but we are never presented with perhaps the good ones. In face, according to Kravitz, “ [lactic acid] is a temporary neutralizer or buffer to the cells elevated accumulation of protons during high-intensity exercise. [Therefore, lactic acid] is an excellent indirect market for the metabolic condition of the cell.” Lactic acid is actually not as bad as one would think. Since the negative side tends to be more noticeable then the good sides, the fact that lactic acid is an indicator for the body that the muscles are being worked too hard is not seen. As Kravitz says “ [lactic acid] production is therefore good and not bad for contracting muscle” According to Andersen, “lactic acid actually serves as a performance enhancing chemical, rather than being the cause of muscle fatigue.”

    Moving on to the negative effects, it is known that soreness is involved but there are actually more serve effects if lactic acid is allowed to be built up. As Quinn(2003) says, “It is necessary to maintain the proper degree of acidity in the cell because when acidity increase important contractile and metabolic functions are hindered.” As we know that there are optimal pH for enzymes in the body to work. Since lactic acid does have that much of effect on pH, there are still body functions that it can interrupt. It is important for people to know this because people could possibly neglect the importance of lactic acid build up. One might think that going to workout intensely for 3 hours and coming back to work he might have a clear mind. The lactic acid build up has already weakened his thought process, affecting his overall performance.

    It is seen that lactic acid can be both good and bad, depending on what perspective one is looking at the subject. If you are the person who gets annoyed when your muscle becomes sore, they you obviously won’t think high of it. If you appreciate the fact that lactic acid tells the body when it has to stop then it would be considered good.

    Andersen, J. B. (n.d.). LACTATE: GOOD, BAD OR BOTH?. The Journal of Experimental Biology. Retrieved January 13, 2014, from <a href="Andersen, J. B. (n.d.). LACTATE: GOOD, BAD OR BOTH?. The Journal of Experimental Biology. Retrieved January 13, 2014, from http://jeb.biologists.org/content/210/17/vii

    -Helmenstine, A. M. (n.d.). What Is Fermentation?. About.com Chemistry. Retrieved January 12, 2014, from http://chemistry.about.com/od/lecturenoteslab1/f/What-Is-Fermentation.htm

    -Kravitz, L. (n.d.). Lactate: Not Guilty as Charged. The University of New Mexico. Retrieved January 13, 2014, from http://www.unm.edu/~lkravitz/Article%20fo

    -Quinn, E. (2003, November 21). Lactic acid does more than cause fatigue.About.com Sports Medicine. Retrieved January 13, 2014, from http://sportsmedicine.about.com/cs/exercisep

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