Yogurt is a fermented dairy product made with live healthy bacteria, specifically Lactobacillus bulgaricus and Streptococcus thermophilus. The bacteria convert lactose in the milk to lactic acid. The acid causes the denaturation of milk proteins resulting in curdling and thickening of the product.


  1. Whole milk
  2. Instant dry milk
  3. Plain yogurt
  4. 8-oz mason jars
  5. Water bath


Before the start of the lab, 8-ounce mason jars will be sterilized in boiling water.

  1. Weigh 5 grams of instant dry milk and add it to an 8-oz mason jar
  2. Weigh 30 grams of plain yogurt and add it to the jar
  3. Fill the jar with whole milk to the ring of the neck (approximately 200 ml of milk)
  4. Mix the contents to dissolve the milk solids and to distribute the yogurt
  5. Cover the jar and allow to sit in the water bath for about 12 hours
  6. Remove the jars from the water bath and cool in refrigerator until ready for use


  • Courtney Simons

    Dr. Courtney Simons has served as a food science researcher and educator for over a decade. He holds a Bachelor of Science in Food Science and a Ph.D. in Cereal Science from North Dakota State University.