Science Fair:

By: Reggan Kuhlman


Why does milk seem to calm a sour stomach? I wanted to see if I could demonstrate what happens when milk and citric acid are combined–how the milk neutralizes the acid in a person's stomach. So I decided to try different beverages (Monster, Red Bull, Sugar Free Red Bull, and Ocean Spray Orange Juice) that contain relatively high amounts of citric acid and mix them with milk to see what would happen. In theory, the beverage with the highest citric acid content should produce the most dramatic reaction when combined with the milk.


Because it is known that orange juice is highly acidic, I predict that the orange juice will have the greatest reaction with the milk.


Before I could experiment with each beverage, I first needed to gather my materials. The beverages I had needed were:

  • 2% milk
  • 1 can of Monster energy drink
  • 1 can of Sugar-Free Red Bull
  • 1 can of Regular Red Bull
  • 1 bottle of Ocean Spray Orange Juice

In addition, I also needed:

  • four small glasses
  • a liquid measuring cup
  • a timer/stopwatch
  • pencil/paper and a camera to document and evaluate the results

When I had gotten all of my supplies, I took a measuring cup and measured half of a cup of milk, and poured it into a glass. I repeated this 3 more times, rinsing the measuring cup out each time. I then poured the Ocean Spray orange juice into the rinsed-out measuring cup until it reached the 1/4 line, and poured it into 1 of the 4 glasses. Right after all of the orange juice was poured in, I pressed the "Start" button on a timer that I had set beforehand for 10 minutes. The other 3 beverages were also poured and started at the exact same time as the orange juice. After the 10 minutes, I simply repeated the steps 2 more times.

Background knowledge:

Before this experiment, I knew little information about this topic. In fact, all I knew about this topic was that milk calms a sour stomach. So I was very excited to do this experiment because I knew I could learn while doing it too.


The following pictures show how each beverage reacted to the milk.


As I went through my data, I discovered that overall, Monster had the greatest chemical reaction when mixed with the milk, considering tests 1 & 3. Orange juice, on the other hand, consistently reacted the poorest in all three tests. The results from both Red Bull varieties were fairly inconsistent, however the Sugar Free Red Bull seemed to out-perform the regular Red Bull. The Sugar Free Red Bull had different ratings, with it's first test having a rating of 3, it's second test having a 1, and its third test having a 2. As for the Regular Red Bull, it had a rating of 3 for the second & third tests, while it's 1st test had a 2.


After three different tests, it was determined that the Monster energy drink had the most dramatic reaction to being combined with the milk. The combining of the two liquids made the milk curdle the best, resulting in a change from a liquid to more of a solid state, which leads me to believe why milk is so effective at calming a person's sour stomach.