Plays an essential role in chain termination during de novo fatty acid synthesis (Probable). Possesses thioesterase activity for medium chain acyl-ACPs. Main substrate is 14:0 (PubMed:21831316). H2O + tetradecanoyl-[ACP] = H(+) + holo-[ACP] + tetradecanoate Belongs to the acyl-ACP thioesterase family.