Research Journeys Update: Dongjoo Kim, Citrus Greening Disease and the Benefits of Kombucha

Dongjoo Kim smiling at the camera, citrus greening disease | Food Science and Human Nutrition UF/IFASWe are thrilled to welcome back Dongjoo Kim, a recent graduate of the Food Science and Human Nutrition Department at the University of Florida! Last year, Dongjoo shared details of his research during the first semester of his food science master’s program in our Research Journeys series.

Now, he is back for another installment in which he discusses the results of his research into citrus greening disease, the changes in his project over time, and what he wishes he knew going into his graduate program.

In his first article, Dongjoo describes his research into the devastating Huanglongbing, or citrus greening disease. This disease has caused extreme damage to the Florida citrus industry. By developing products such as kombucha with citrus greening disease-tolerant cultivars, Dongjoo hoped to support the citrus industry in its recovery. Read on to learn how his project developed and concluded.

When we last heard from you, your research studying how kombucha made from Sugar Belle—a citrus greening disease-tolerant cultivar—could aid the Florida citrus industry was in its initial stages. What did you discover over the past year and a half?
Sugar Belle kombucha in a jar, citrus greening disease | Food Science and Human Nutrition UF/IFAS
Sugar Belle kombucha
Regular kombucha in a jar, citrus greening disease | Food Science and Human Nutrition UF/IFAS
Regular kombucha

I continued my research on Sugar Belle (SB) kombucha. After several failed fermentations, I finally learned how to ferment SB juice without messing up. My research focused on seeing the changes in aroma and taste compounds during kombucha fermentation and seeing the correlation between the chemical composition and the sensory attributes.

To do so, I used Gas Chromatography-Mass Spectrometry/Olfactometry (GC-MS/O) for aroma compounds and Liquid Chromatography-Mass Spectrometry/Mass spectrometry (LC-MS/MS) for taste compounds. I also conducted sensory testing for overall liking, flavor liking, and the intensity of the sensory attributes, such as sweet, sour, bitter, astringency, and so on—albeit with a small number of internal panelists due to the pandemic.

From these analyses, I discovered positive characteristics of the Sugar Belle kombucha.1 First, Sugar Belle kombucha showed higher levels of terpenes and terpenoids, compounds that have health benefits such as antidiabetic and antioxidant effects.2 Moreover, these terpenes positively correlated with overall liking and flavor liking. In terms of the taste compounds, Sugar Belle kombucha had higher concentrations of organic acids and flavonoids, which have anticancer and anti-inflammatory effects.3

The sensory testing also showed no significant differences in overall and flavor likings of the SB kombucha compared to regular kombucha made from fermented green or black tea. Since the market size of kombucha is expected to grow by 22.35 percent each year between 2022 to 2027,4 SB kombucha has the potential to reduce the negative effects of citrus greening disease by adding a lucrative use for the SB cultivar.

Four glass jars with plant extracts in a row
Plant extraction samples from Dongjoo’s work as a lab technician.
How did your research project change from the first semester of your graduate program to the last semester? Why did it change?
Jar with dark liquid on a lab bench
Plant extraction samples from Dongjoo’s work as a lab technician.

Initially, I had a broad concept and plan for my research and did not have any detailed research plans. My advisor, Dr. Yu Wang, taught me how to approach my work. Through trial and error during the fermentation process and analysis of the kombucha, I learned to be more independent in my research.

My original plan was to compare Sugar Belle kombucha and regular kombucha by studying their aroma and taste compounds as well as their sensory attributes. But as time went by, I was curious about other citrus fruits such as tangerines, grapefruits, and Valencia and Hamlin oranges. So I made kombuchas using those fruits and measured the pH and Brix (sugar content) during the fermentation. I found little difference among the citrus kombuchas except for the SB kombucha. To analyze the differences in aroma and taste compounds between kombuchas without being redundant, I chose to study Hamlin, a typical sweet orange, and Sugar Belle, an HLB-tolerant mandarin hybrid.

How did you relax and recharge while working on your research project?

I liked to go for walks near my research lab at the Citrus Research and Education Center (CREC) in Lake Alfred, FL. While walking, I would take a deep breath and get some fresh air. In the orange blossom season, you can smell a very sweet and pleasant aroma from the orange flowers near the center. This aroma wakes me up and organizes my mind.

During the weekends, I recharged myself by taking a nap, usually two to three hours long. I would also try something special that I don’t eat during the weekdays—a kind of special treat for me such as Dakgangjeong (sweet and spicy Korean fried chicken), Tteokbokki (Korean spicy rice cakes), or sushi.

Sunny day outside the Citrus Research and Education Center in Lake Alfred
The area outside the Citrus Research and Education Center in Lake Alfred where Dongjoo enjoyed taking walks.
What do you wish you had known going into your graduate program?
Dakgangjeong (sweet and spicy Korean fried chicken)
Tteokbokki (Korean spicy rice cakes)
Tteokbokki (Korean spicy rice cakes)

The COVID-19 pandemic started just after the spring break of my first semester. As we all know, the first year of COVID-19 began with a complete lockdown, so I did not get to enjoy life in Gainesville.

Since my lab is located in the CREC, I had to move down to Lake Alfred for my research in the second year of my master’s program after the lockdown measures started to lift. I wish I had known COVID-19 would strike so that I would have been more involved in social activities and made more trips to places in and near Gainesville before the pandemic hit.

You graduated last December—congratulations! What are you working on now?

I am a lab technician working in the same lab as my master’s program. Currently, I’m working with a postdoctoral associate on plant materials. We are studying the extraction of compounds. This research is different from what I did during the master’s program, so I am learning a lot. I think of this as an opportunity to broaden my research skills.

Is there anything else you would like to add about your experience in the FSHN graduate program?

Having worked as an intern in the FSHN department in 2018 and completed the master’s program during 2020-2021, I can say that the people in the department are all friendly and nice to each other. Students, faculty, and staff have been very supportive. The department has a positive energy that makes people comfortable. I could not do my master’s work without the efforts of those in the department. I would like to say thank you all!

Dongjoo was born and grown in the Seoul Metropolitan area of South Korea. He majored in chemistry and food & nutrition at Hanyang University in Seoul, South Korea and obtained a master’s degree in Food Science and Human Nutrition at the University of Florida. He is currently working as a lab technician specializing in flavor chemistry in Dr. Yu Wang’s lab in the Citrus Research and Education Center at the University of Florida, in Lake Alfred, FL. He is continuing his Ph.D. studies in food science at UF starting in the fall of 2022. In his free time, he often tries to make something delicious.

  1. Kim, D.; Wang, Y. Health‐beneficial Aroma and Taste Compounds in a Newly Developed Kombucha Using a Huanglongbing‐tolerant Mandarin Hybrid. Journal of Food Science 2022, 1750-3841.16170.
  2. Murali, R.; Saravanan, R. Antidiabetic Effect of D-Limonene, a Monoterpene in Streptozotocin-Induced Diabetic Rats. Biomedicine & Preventive Nutrition 2012, 2 (4), 269–275.
  3. Vīna, I.; Linde, R.; Patetko, A.; Semjonovs, P. Glucuronic Acid from Fermented Beverages: Biochemical Functions in Humans and Its Role in Health Protection. Int. J. Res. Rev. Appl. Sci. 2013, 14, 217–230.
  4. Mordor Intelligence. Mordor Intelligence. KOMBUCHA MARKET – GROWTH, TRENDS, COVID-19 IMPACT, AND FORECASTS (2022 – 2027); 2021.
Looking for more posts exploring graduate research projects in the Food Science and Human Nutrition Department at the University of Florida?

Revisit Dongjoo’s first year in M.S in Food Science program here.

Dive into the Research Journeys of other graduate students below.

M.S. Food Science
M.S. Nutritional Sciences
Ph.D. Food Science
Ph.D. Nutritional Sciences


Jessie Erwin, Nutrition Communications Consultant for the UF/IFAS FSHN department.
Posted: June 6, 2022

Category: Food Science & Human Nutrition
Tags: Citrus, Citrus Greening Disease, CREC, Dongjoo Kim, Dr. Yu Wang, Food Science Graduate Student, FSHN Research Journeys, Graduate Program, Graduate Research, Graduate Student, Hamlin Cultivar, Huanglongbing, Kombucha, Masters Student Research, Research Journeys, Research-journeys-food-science, Research-journeys-food-science-ms, Sugar Belle, Sugar Belle Kombucha, UF/IFAS Citrus Research And Education Center

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