Why curd turns bitter sometimes?

Curd can turn bitter due to several reasons, primarily related to bacterial activity. Certain bacteria, such as Bacillus cereus, can produce bitter-tasting compounds during fermentation or spoilage. Additionally, if the milk used to make the curd is of low quality or has been stored improperly, it can lead to the growth of undesirable microorganisms that contribute to bitterness. Lastly, excessive heat during pasteurization or cooking can also affect the flavor profile of the curd.