Final answer:
TCS foods should be discarded if they've been out of the temperature control zone (41°F-135°F) for more than 4 hours to ensure food safety and prevent foodborne illnesses.
Step-by-step explanation:
When the question asks to 'Discard TCS if out of temp. zone for more than ____,' it is referring to a guideline in food safety practices. TCS foods, or Time/Temperature Control for Safety foods, must be kept within specific temperature boundaries to prevent the growth of pathogenic microorganisms and the formation of toxins. The generally accepted rule in the foodservice industry is to discard TCS foods if they have been out of the temperature control zone, which is below 41°F (5°C) or above 135°F (57°C), for more than 4 hours. This is critical to ensure the safety and prevent foodborne illness.