Final answer:
Potatoes should be blanched at a temperature between 150°C and 250°C when making french fries.
Step-by-step explanation:
When making french fries, potatoes should be blanched at a temperature of between 150°C and 250°C. This temperature range ensures that the potatoes are cooked through and have a crispy exterior. Blanching at a higher temperature results in a faster cooking time and a more crispy texture. It is important to consider the oil temperature and cooking time to achieve the desired result.