What flavor defect in milk is often associated with bacterial contamination?

Sour or rancid flavors in milk are commonly associated with bacterial contamination, particularly by the types of bacteria that produce lactic acid during fermentation. This process can result in a decrease in pH, resulting in a sour taste. Additionally, certain bacteria can produce off-flavors and can cause milk to develop rancidity by breaking down fats and creating undesirable compounds.

These defects are often the result of poor handling or storage practices, which allow bacteria to proliferate. Maintaining proper hygiene and refrigeration temperatures is essential to minimize the risk of bacterial growth and the resultant sour or rancid flavors in milk. Other flavor profiles such as sweet, chocolate, or spicy are not typically indicative of bacterial activity and arise from different factors, including milk source and additives or processing methods.