Telling the truth is very important as the Torah writes "distance yourself from a lie" (Shemot 23:7). The parameters of telling the truth vary though and there are four types of circumstances where one can bend the truth (adapted from Hershey H. Friedman and Abraham C. Weisel article on the topic)
- for the sake of peace (classic case is God changing Sara's works when repeating them to Avraham)
- to be pleasant with people (classic case is to praise a bride in front of her groom on their wedding day, Ketubot 17a)
- for the sake of humility, modesty or to protect others
- to protect oneself from financial harm
The first three are relevant to your case. The authors further bring R Isaiah diTrani (Tosefot RI"D) who notes that the opinion of the Sages is that one has to be pleasant with people even if it means that he has to lie. The Ritva states in an unambiguous manner that wherever one has to be concerned about "the ways of peace" there is no prohibition of "Distance yourself from a false matter."
Elsewhere R Ari Enkin brings writes "that bestowing an undeserved compliment is to be preferred over saying a truth which would insult another person" and, to your specific case, that "one should not say that the food one had been served tastes bad and is not how one would have preferred it."
Chabad also writes (using the above gemara in Ketubot) that "a white lie said in order to protect someone from embarrassment".
There is a story about R Moshe Feinstein (brought in his biography) that, before he married, his meals were prepared by a local woman where he ate for years. He always complimented his host on her cooking. Once, a sister came to visit and found the food horribly salted. R Moshe explained this was always the case but he couldn't bring himself to correct his host and possibly risk offending her.