To properly sanitize milk lines and equipment, water must be circulated in place at a minimum temperature of ________ for at least 5 minutes.

The correct answer is based on the requirement for effective sanitation of milk lines and equipment. To ensure that harmful microorganisms are effectively killed, it is essential to use water at an elevated temperature.

The choice of 77 degrees C (170 degrees F) is significant because this temperature is widely recognized as sufficiently high to achieve proper sanitation in dairy processing. At this temperature, the thermal energy penetrates surfaces, helping to dissolve and remove any residues, while also effectively inactivating bacteria, yeasts, and molds that could contaminate milk. The specified duration of at least 5 minutes is crucial; it allows the high-temperature water to circulate thoroughly, ensuring that all surfaces come into adequate contact with the sanitized water.

Lower temperatures, such as those found in the other options, might not be effective for the required sanitation process, as they fail to reach the levels necessary to reliably eliminate pathogens and ensure the safety and quality of the milk being processed.