What is
Clabber is a food produced by allowing unpasteurized milk to turn sour at a specific humidity and temperature. Over time, the milk thickens or curdles into a yogurt-like substance with a strong, sour flavor.
  
Soured milk is a food product, distinguished from spoiled milk, and is a general term for milk that has acquired a tart taste, either through the addition of an acid, such as lemon juice or vinegar, or through bacterial fermentation.