The ruling on tasting Food during fasting
Question :
Is it permissible for the cook to taste his food to make sure that it tastes right while he is fasting?
Answer:
There is no harm in tasting the food if there is a need for it. This is by the person placing it on the tip of his tongue so that he may know its sweetness and saltiness and their opposites. However, he should not swallow any of it. Rather, he should spit it out or expel it from his mouth and his fast will not be corrupted by that, if Allâh, the Most High wills.
Source:
Ash-Shaykh Ibn Jibreen
Fatawa Islamiyah, Vol. 3 Page 264