Step 1: Understanding the Concept:
The question identifies "cheesy" as a specific off-flavor in butter, distinct from sour, rancid, or cooked flavors, and asks for its cause.
Step 2: Detailed Explanation:
(A) Growth of proteolytic bacteria in cream: Proteolytic bacteria produce proteases, enzymes that break down casein proteins. This breakdown generates peptides and compounds characteristic of aged cheese flavors. Growth of these bacteria in cream before churning transfers these flavors to the butter, causing the cheesy defect. This is the correct answer.
(B) Over heating of cream: Overheating causes a "cooked" or "scorched" flavor due to whey protein denaturation and heat-induced reactions.
(C) Over neutralization of cream: Excessive neutralizer addition results in a soapy or "neutralizer" flavor.
(D) Use of sour cream: Sour cream (high acidity) produces butter with a sour or acidic taste, not a cheesy flavor.
Step 3: Final Answer:
The cheesy flavor defect in butter is due to protein breakdown products from proteolytic bacteria growth in the cream.