。
Refrigerators prevent food from spoiling.
Literal
Refrigerator [topic-は] food [of-の] spoilage [object-を] prevents.
A concise, textbook-style definition. 腐敗 ('decay, spoilage') is the Sino-Japanese noun form of the verb 腐る ('to rot'). 防ぐ ('to prevent, defend against') takes を on the thing prevented. Using the Sino-Japanese noun form rather than the native verb gives a more formal framing — common in scientific or instructional writing.