Whoever eats fat, or dried meat, or wheat even if just a bite, must perform expiation; because this is intended for eating. However, if he chewed a sesame seed or something similar that requires expiation and it disintegrated while chewing, and he did not find any taste in it, then there is no expiation, and his fast is not invalidated. Refer to Bada'i' al-Sana'i' 2: 99-100.