What is the maximum microwave oven temperature (in Celsius) that should not be exceeded during processing?

• A. 68 C
• B. 100 C
• C. 25 C
• D. 0 C

Answer: (A)

When using microwaves to speed up tissue processing, heat must be controlled because excess temperature can denature proteins, distort tissue morphology, and even damage antigenicity. The upper limit commonly used in practice is about 68 C, which provides faster processing without pushing the tissue into thermal damage. Reaching 100 C would mean boiling, causing loss of reagents, tissue disruption, and artifacts. A temperature of 25 C is too low to drive the necessary chemical changes efficiently, and 0 C would freeze the tissue, stopping processing altogether. Therefore, the maximum safe temperature to avoid exceeding during processing is 68 C.