Editor’s note: Though the NHSJS usually features work by high schoolers, it occasionally gets the chance to showcase extraordinary research done by young scientists across the country. This project was done by a student in third grade – we hope you enjoy it.
The project investigates whether the external application of turmeric reduces the growth of fungi and bacteria in foods.
Turmeric (Curcuma longa) is a rhizomatous herbaceous perennial plant of the ginger family, Zingiberaceae. It is native to tropical South Asia and needs temperatures between 20 °C and 30 °C and a considerable amount of annual rainfall to thrive.1
When not used fresh, the rhizomes are boiled for several hours and then dried in hot ovens, after which they are ground into a deep orange-yellow powder commonly used as a spice in curries and other South Asian and Middle Eastern cuisine, for dyeing, and to impart color to mustard condiments. The active ingredient in turmeric is curcumin, which has a distinctly earthy, slightly bitter, peppery flavor and a mustard smell. Tumeric has been used for over 2500 years inIndia, originally as a dye. It has become the key ingredient for many Indian, Persian and Thai dishes, not only in curry, but also in many more foods. Turmeric, which has a food additive code of E100, is also used to protect food products from sunlight.2
The medicinal properties of this spice have been slowly revealing themselves over the centuries. Long known for its anti-inflammatory properties, turmeric has been deemed a natural wonder by recent research, proving beneficial in the treatment of many different health conditions from cancer to Alzheimer’s disease. It is also a natural antiseptic and antibacterial agent, useful in disinfecting cuts and burns.3
If turmeric is applied to foods, then the growth of bacteria and fungi will be suppressed.
- Two pieces of white bread
- Four pieces of strawberry
- One cup of milk
- Ten grams of turmeric powder
- Methylene Blue
- 4 test tubes
- Liquid Dropper
The control group in this experiment are the bread, strawberries, and milk without turmeric.
Steps to conduct experiment using milk:4
- Obtain 4 sterilized test tubes to begin the experiment.
- Fill each about 3/4th of each test tube with milk.
- Add 1 tsp of turmeric into 1 test tube creating turmeric milk solution into one test tube, 2 tsp in the 2nd test tube and 3 tsp in the 3rd test tube. Leave the last one as is with just plain milk.
- Add a drop of Methylene blue to each test tube.
- Measure and record the amount of time in days taken for the contents of each test tube to turn white.
Steps to conduct experiment using bread and strawberries:
- Take 2 pieces of white bread and 4 strawberries.
- Soak one piece of white bread and two strawberries in water for 5 seconds..
- Apply approximately one tea spoon of turmeric to one piece of white bread and two strawberries. Care should be taken that the turmeric covers the entire piece uniformly.
- Observe all pieces of bread and strawberries for the next 8 days. Check results and take photographs every day. The quantity of fungus should be categorized from 1-5,1 being the lowest amount and 5 being highest.
- The difference in pathogen levels between the control group and the experimental group should be documented on a daily basis.
Experiment 1: Milk Result: Hypothesis verified
The contents of the test tubes with turmeric took an average of 7 to 15 hours longer (depending on the amount of turmeric) to turn white in Meth. Blue Test compared to the control test tubes with plain milk. Graph1 below charts the amount of turmeric in milk to the time it took for the milk to spoil. This happens due to the fact that milk containing living bacteria (known commonly as “spoiled milk”) will decolorize methylene blue. The reaction in this instance is caused by an enzyme associated with the microorganisms, and most probably is an oxidation-reduction in which the methylene blue acts as a hydrogen acceptor5. Turmeric appears to inhibit microorganism growth in milk.
Graph 1: Charting the amount of turmeric to the growth of bacteria in milk.
Test tubes holding more turmeric took longer to change color than test tubes with less turmeric.
Figure 1: Test tubes with milk and turmeric Figure 2: Results of the milk experiment.
Experiment 2: Bread Result: Hypothesis partially verified
Bread with turmeric had less fungus than bread without turmeric. The difference in fungus quantity was noticeable but not too significant.
Figure 3: Bread pieces with and without turmeric
Experiment 3: Strawberry Result: Hypothesis not verified
There was not a very significant difference in the quantity of fungus on the strawberries. We used 4 strawberries for the experiment and 2 of them were coated with turmeric but all four of them seemed to spoil around the same time. However, a source of error could potentially be the difference in ripeness of the strawberry samples selected. Strawberries in general spoil really fast once taken out of the refrigerator, so it is possible that the effect of turmeric in reducing the amount of pathogen growth was not visible in the strawberries.
Graph 2: Results of experiment with bread and strawberry
The hypotheses were partially correct. I was able to demonstrate an antimicrobial effect of turmeric, but only with milk and partially with bread. There was no change observed with strawberries. In milk I observed a visible difference in the time it took for bacterial growth. Essentially when methylene blue is added to milk, the color initially changes from milky white to blue. However, as the milk spoils it turns white again. As mentioned before, milk containing living bacteria (known commonly as “spoiled milk”) will decolorize methylene blue.
This study has demonstrated that turmeric can prevent bacterial and fungal growth in selective foods, such as milk. Therefore adding turmeric to your diet may help in preventing or even treating food-borne bacterial illnesses. Further studies would test the efficacy of turmeric microbe inhibition on other foods, and perhaps deduce a mechanism by which turmeric acts to achieve this result.
- http://en.wikipedia.org/wiki/Turmeric [↩]
- Turmeric: the golden spice of life. (n.d.). Retrieved from http://www.turmeric.co.in/turmeric_powder.htm [↩]
- Goyal, Rajat. The study of turmeric as an effective antiseptic agent against Escherichia coli strain k-12 Bacteria, version 6, Knol. 18 Feb. 2010. [↩]
- Mital, Sonya. Got Turmeric? The Magic Spice! Investigating the Anti-Bacterial Properties of Turmeric on the Shelf Life of Milk, retrieved from http://www.usc.edu/CSSF/History/2009/Projects/J1716.pdf [↩]
- Whitehead, Hugh R. The reduction of methylene blue in milk; The influence of light. From the Dairy Research Institute, Massey Agricultural College, University of New Zealand. [↩]