Chapter 51: 1-3
Blessings After Eating
1. The blessing borey nefoshos... is recited after partaking of: fruit from
trees, with the exception of the seven fruits [with which Eretz Yisroel is
blessed], fruit that grows on the ground, vegetables, and all foods that
are not products of the land.
Both eating and drinking can be covered by a single blessing.
2. Neither, a b'rochoh achronoh nor the grace after meals should be recited
unless one ate the minimum measure of food that is considered significant -
i.e., a k'zayis.*
* {As mentioned, there is a debate among the authorities regarding the
equivalent of a k'zayis in modern measure. According to Shiurei Torah, this
measure is approximately 31 grams and the Chazon Ish, at approximately 36
grams.}
With regard to beverages, some maintain that a b'rochoh achronoh is
required only if one drank a revi'is,* while others maintain that even with
regard to liquids, a person who drinks a measure equal to a k'zayis is
obligated to recite a b'rochoh achronoh. Therefore, because of the doubt
involved, one should take care to drink less than a k'zayis or more than a
revi'is. There is no difference in this regard between alcoholic beverages
and other liquids.
3. There are certain authorities who maintain that everything which is by
nature a single entity - e.g., a single nut, or other fruit, even a single
bean - since it is a complete fruit, is significant enough to require a
b'rochoh achronoh even though is smaller than a k'zayis.
Others do not accept this principle. Therefore, to prevent a doubt from
arising, it is proper not to eat less than a k'zayis of such produce. If
the produce was divided before it was eaten, its unique importance is
nullified, and all authorities agree that a b'rochoh achronoh is not
recited for less than a k'zayis.