Yes, mold can grow on milk. Most mold thrives in temperatures between 60-80 degrees Fahrenheit, so typically milk will only mold if left out at room temperature. In the refrigerator, milk typically will curdle. This happens when there is an increase in lactococci, lactobacilli or other bacteria. Although the milk will stay white, it will have a sour smell and should not be consumed.
Updated on Wednesday, February 01 2012 at 01:08PM EST