Science, Tech, Math › Science How to Test for Protein in Food An Easy Method Using Calcium Oxide Share Flipboard Email Print Science Activities for Every Subject Introduction Weather Make a Storm Glass to Predict the Weather Make a Simple Weather Barometer Make Real Snow Make a Cloud in a Bottle Determine Why the Sky Is Blue Food and Cooking Determine Vitamin C by Iodine Titration Make Biodiesel From Vegetable Oil Test for Protein in Food Experiment With Fruit Ripening and Ethylene See How Much Sugar Is in Soda Fire and Smoke Make Colored Fire Make a Smoke Bomb Make Chemical Fire Perform Magic Tricks With Fire Make a Sparkler Bubbles Make Bubbles That Don't Pop Make Glowing Bubbles Make a Giant Bubble Using Dry Ice Make a Bubble Rainbow Crystals Grow Bismuth Crystals Grow a Big Alum Crustal Grow a Borax Crystal Snowflake Grow Copper Sulfate Crystals Grow Table Salt or Sodium Chloride Crystals Chemical Reactions Build a Baking Soda Volcano Make Sulfuric Acid at Home Make Homemade Dry Ice Make Hydrogen Gas Make "Elephant Toothpaste" Maximilian Stock Ltd. / Getty Images By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated November 07, 2019 Protein is an essential nutrient that builds muscle in the body. It's also easy to test for. Here's how: Protein Test Materials Calcium oxide (sold as quicklime in building supply stores)Red litmus paper (or another method to test pH) WaterCandle, burner, or another heat sourceEye-dropperTest tubeMilk or other foods to test Procedure Because milk contains casein and other proteins, it's a good food to start your testing with. Once you understand what to expect from testing milk, you can examine other foods. Add a small amount of calcium oxide and five drops of milk to a test tube.Add three drops of water.Dampen the litmus paper with water. Water has a neutral pH, so it should not change the color of the paper. If the paper does change color, start again using distilled water rather than tap water.Carefully heat the test tube over a flame. Hold the damp litmus paper over the mouth of the test tube and observe any color change.If protein is present in a food, the litmus paper will change color from red to blue. Also, smell the test tube: If protein is present, you should be able to detect the odor of ammonia. Both of these indicate a positive test for protein. If protein is not present in the test sample (or is in insufficient concentration to produce adequate ammonia during testing), the litmus paper will not turn blue, resulting in a negative test for protein. Notes About the Protein Test Calcium oxide reacts with protein to break it down into ammonia. The ammonia changes the acidity of the sample, causing a pH change. If your food is already very alkaline, you won't be able to use this test to detect protein. Test the pH of food to see if it changes the litmus paper prior to performing the protein test.Milk is an easy food to test because it's a liquid. To test solids, such as meat, cheese, or vegetables, you must first grind the food by hand or by using a blender. You may need to mix the food with some water to make a sample you can test.The test registers a change in pH, which is the concentration of hydrogen ions in an aqueous or water-based solution. Most foods contain water, so they work fine for the test. However, oily foods may not work as well. You can't test pure vegetable oil, for example, because it doesn't contain any water. If you test greasy foods, such as french fries or potato chips, you'll need to mash them up and mix them with a bit of water first.