Making A Brachah Acharonah when Eating Less than a Kezayis
The minimum amount of food that requires a brachah acharonah, an after-blessing, to be said after eating it, is a kezayis, the volume of an olive, which according to halachah is approximately the equivalent of half an average-sized egg (or, according to some, just under a third of an egg). However, if one ate a briyah (a.k.a. beryah), a naturally whole item, even if it is smaller than a kezayis, such as a grape, a pea, or perhaps a single section of a mandarin, according to some poskim such an item requires a brachah acharonah to be said. In order to avoid this question, one should always eat more than a kezayis or not eat a briyah. If a person does not eat the pits or the seeds in a place where they are commonly eaten, or if a small piece is cut off and not eaten, it is not considered a whole briyah, and the question is rendered moot.