Related do Keritot 3:3

One who eats, one who drinks, and one who anoints himself with terumah [unwittingly must repay its value and a fifth (Ter. 6:1)]. If he ate [terumah] and came back and ate again, if the time [that elapsed from] when he started eating until he finished eating is less than the amount of time to eat a p'ras (half a loaf of bread), [the two acts of eating] join together [for purposes of liability], and if not, they do not join together. If he drank [terumah] and came back and drank again, if [the elapsed time] from the first drinking to the last drinking is less than the amount of time to drink a revi'it (a quarter-log), [the two acts of drinking] join together, and if not, they do not join together. [Moreover,] just as eating an olive's bulk [triggers liability], so too drinking an olive's bulk [triggers liability]. Eating and drinking do not join together [for purposes of liability]. If he ate an olive's bulk, even from five different types of food, behold, all these join together [if all the eating was in a short time period]. If he ate half of an olive's bulk, and it became known to him [that he was eating terumah], and then he came back and ate another half of an olive's bulk [of terumah] afterwards from a different kind [of food], behold, these do not combine.