A Summary of the Halakhot of Berakha Acharona
Just as one says a blessing before eating and drinking, so too afterwards one must express gratitude to God, through reciting a berakha acharona. In order to become obligated to say a berakha acharona, one must eat or drink a minimal amount, a shiur, within a certain amount of time. What is the shiur of food, or drink, one must consume, and within how much time? Furthermore, what is the halakha when one eats different foods, or foods and liquids?
The Shi’ur of Eating for a Berakha Acharona
The Talmud (Sukka 6a) teaches that “most of its measurements are a ke-zayit (the size of an olive).” Indeed, throughout the Talmud, we see that the minimum amount that one must eat in order to fulfill a mitzva or for which one is punished is generally a kezayit. In this context as well, regarding the berakha acharona, the Talmud (Berakhot 37b) relates:
Moreover, R. Hiyya b. Abba said: I have seen R. Yochanan eat salted olives and say a blessing both before and after… R. Yirmiya asked R. Zeira: How could R. Yochanan make a blessing over a salted olive? Since the stone had been removed, it was less than the minimum size! He replied: Do you think the size we require is that of a large olive? We require only that of a medium sized olive, and that was there, for the one they set before R. Yochanan was a large one, so that even when its stone had been removed, it was still of the requisite size. For so we have learnt: The olive spoken of means neither a small nor a large one, but a medium one.
The Rif (Berakhot 27a) derives from this passage that while one must say a blessing before eating even the smallest amount, as it is prohibited to benefit from this world without a blessing (Berakhot 35a), one only says a berakha acharona after eating the equivalent of a ke-zayit, the size of an olive. Tosafot (38a s.v. batzar), the Rosh (Berakot 6:16), and other Rishonim arrive at the same conclusion.
Why is a berakha acharona only said after eating a kezayit of food, unlike a berakha rishona, which is said before tasting even the smallest amount?
Rashi (39a, s.v. batzar) explains that the obligation to say Birkat Ha-Mazon, the model for every berakha acharona, is derived from the verse (Devarim 8:10), “And you shall eat, and be satisfied, and bless the Lord your God.” The minimum amount that is considered to be an act of “eating” is a ke-zayit. Thus, only eating a ke-zayit is considered to be an act of “eating” that warrants a berakha acharona. Alternatively, we might suggest that the Rabbis established that one must say a berakha acharona after deriving benefit from a “significant” quantity of food (and not just any benefit). Generally, a ke-zayit is viewed as a significant amount. Therefore, one who eats (and derives benefit from) a ke-zayit of food must say a berakha acharona.
There may be halakhic ramifications to this question.
Birya – A Complete and Natural Whole Unit of Food
The Yerushalmi (Berakhot 6:1) implies that one must say a berakha acharona even after eating a “birya,” something in its whole, natural form, such as a grape or a pomegranate seed.
Tosafot (ibid.) understand that the Yerushalmi argues with the Talmud Bavli – which, as we saw above, teaches that one says a berakha acharona after eating a ke-zayit – and the halakha is in accordance with the Bavli. This is the view of the Rif (ibid.) and the Rambam (Hilkhot Berkahot 3:12) as well. Other Rishonim (R. Yosef cited by Tosafot above; Rosh ibid.; Rashba 39a; Rabbeinu Yona 27b, et. al.) raise the possibility that the Yerushalmi does not argue with the Bavli; the passage from the Bavli refers to an olive that is not whole. The Rosh even recommends that one refrain from eating a birya that is less than a ke-zayit due to this debate.
Seemingly, we might suggest that according to Rashi, one should certainly not say a blessing after eating a birya smaller than a kezayit, as eating less than a ke-zayit is not considered to be an act of “eating.” However, if a berakha acharona is said after benefiting from a “significant” portion of food, then one could argue that although a birya lacks size, it has “importance” (as is seen in numerous other halakhot; see Makot 13a, Chullin 100b and 119b), and it is therefore worthy of a berakha acharona.
The Shulchan Arukh (210:1) rules that one should only say a berakha acharona after eating a ke-zayit of food. He cites the debate above and writes “some express doubt whether one says a blessing after [eating] over something which is a birya, such as a single grape or pomegranate seed, even though it is smaller than a ke-zayit; therefore, one should be careful not to eat a birya which is less than a ke-zayit.” If one bites into the birya and does need eat it in one bite or one does not eat its pit (such as the pit of a date, an olive, or a cherry), it is not considered to be a birya (see Mishna Berura 210:7).
The Shi’ur for Borei Nefashot
Interestingly, the Rishonim question whether the shiur of ke-zayit is relevant only to the blessing of Al Ha-Michya (and Birkat Ha-Mazon), or to Borei Nefashot as well. Tosafot (ibid.; see also Rosh ibid.) records:
The Ri says: Regarding Borei Nefashot, since it is not “an important blessing” (lav berakha chashuva hi), even [upon eating] less than the measurement [of a ke-zayit], one says Borei Nefashot. It seems that since Borei Nefashot corresponds to the blessing of Al Ha-Gefen, just like the Al Ha-Gefen requires a shi’ur, so too [Borei Nefashot] needs a shi’ur.
The Rambam (ibid.) and Rid (ibid.) clearly disagrees and maintain that even the blessing of Borei Nefashot is only said after eating (or drinking) a shiur.
Here, we may suggest a fundamental difference between Al Ha-Michya and Borei Nefashot. As Rashi (above) explains, the blessing of Al Ha-Michya may depend upon an act of “eating,” which by definition entails eating a ke-zayit. However, Borei Nefashot doesn’t relate to a specific food, as we can see from the text of the blessing:
Blessed are You … Creator of numerous living beings and their needs, for all the things You have created with which to sustain the soul of every living being. Blessed is He who is the Life of the worlds.
Therefore, we may understand that the blessing of Borei Nefashot relates to deriving benefit from food or drink, and there therefore may be no need for a specific amount. The halakha is not in accordance with this view.
The Shi’ur Ke-Zayit and a Berakha Rishona
In this context, it is worth noting that almost all Rishonim assume that one says a blessing before eating even the smallest amount of food (or drink) so as not to “benefit from this world without a blessing” (Berakhot 35a). Some, however, note that the Talmud (Berakhot 35a) suggests that the obligation to say a berakha rishona may be derived from a kal ve-chomer from Brikat Ha-Mazon: “One says a blessing when he is satiated; all the more so when he is hungry!” Why, then, were the rabbis stricter regarding a berakha rishona than a berakha acharona?
The Kesef Mishna (Hilkhot Berakhot 6:13) explains:
It seems to me that they said that one should say a blessing on a small amount lest he change his mind and eat a shi’ur [i.e., a kezayit], in which case he needed to have said a blessing beforehand, and now he is unable to fix the matter.
This interpretation implies that theoretically, one should only say a blessing over eating a ke-zayit, an “act” of eating, but for technical reasons, the rabbis said one should say a blessing even when eating less.
Interestingly, the Kolbo (24) cites a view that maintains that whenever one eats less than a ke-zayit, one should say She-Hakol. He further cites R. Achai Gaon (the author of the She’iltot) as opining that one who eats less than a ke-zayit should not say any blessing.
These intriguing positions, which are not accepted le-halakha, seem to maintain that less than a ke-zayit is not considered an “act” of eating and one should therefore either say the generic She-Hakol blessing, which covers all benefit from eating (as we discussed previously), or not at all.
Similarly, the Talmidei Rabbeinu Yona (Berakhot 27b, s.v. ani) suggest that before eating less than a ke-zayit of mezonot, one says She-Hakol. Although one may view an amount of food smaller than the size of an olive as insignificant and not worthy of a separate blessing praising the specific food, one still may not benefit from this world without first reciting a blessing, and at least the blessing of She-Hakol should be recited. Again, the halakha is not in accordance with this view.
The Size of a Ke-Zayit
In Relation to an Egg
How does one measure the shiur of a ke-zayit?
Some Rishonim maintain that one must determine the size of a ke-zayit based upon its relation to the size of a ke-beitza. They arrive at this conclusion based upon an apparent contradiction between Talmudic passages. On the one hand, the Talmud (Yoma 80a) states that the Sages measured that the esophagus cannot hold more than the size of an egg. On the other hand, the Talmud elsewhere (Keritut 14a) teaches that the Rabbis have calculated that the gullet cannot hold more than two olive-sizes at a time. These passages seem to indicate that a ke-zayit is half the size of a ke-beitza.
Based on these passages, a number of Ashkenazic Rishonim, including the Ri (Tosafot, Eiruvin 80b, s.v. agav), the Ra’avia (525), the Terumat Ha-Deshen (139), and the Maharil (Seder Ha-Haggada 31) assert that a ke-zayit is the size of half of an egg (ke-beitza).
It is important to note in this context that an olive (generally 3-6 cc) is nowhere near the size of a half of an egg (generally 50-60 cc). It appears that the Rishonim from North Western Europe (i.e. Ashkenaz) never actually saw an olive, which only grows in the Mediterranean region! Indeed, R. Eliezer b. Yoel Ha-Levi (Germany, c.1140-c.1225), known as the Ra’avia, writes:
And wherever a ke-zayit is required, the food should be measured generously, since we are not familiar with the measurement of an olive, and so that the blessing should not be in vain. (Ra’avia, Berakhot 107)
Therefore, it is not surprising that Ashkenazic Rishonim based their calculation of the ke-zayit upon its relation to the egg, as described by the Talmud.
Other passages, however, point to a different size of a ke-zayit. Regarding the laws of eiruv chatzeirot, the Talmud rules (Eiruvin 80b) that the amount of food for two meals (shtei se’udot) is equivalent to the amount of 18 grogerot (dried figs). Elsewhere, regarding the laws of eiruvei techumin, the gemara (Eiruvin 82b) cites different opinions regarding the amount of food considered to be sufficient for shtei se’udot. According to R. Yochanan ben Beroka, two meals consist of a quantity equivalent to the size of six eggs, while according to R. Shimon, it is slightly less – five and a third eggs. Accordingly, according to R. Yochanan ben Beroka, a grogeret is about a third of the size of an egg (6/18, or 1/3), while according to R. Shimon, a grogeret is slightly larger (8/18).
Based upon these passages, the Rambam (Hilkhot Eiruvin 1:9) rules that two meals equals the volume of 18 grogerot, which are equivalent to 6 medium sized eggs. Since the gemara (Shabbat 91a) records that an olive (ke-zayit) is smaller than a grogeret, a ke-zayit must be smaller than a third of a ke-beitza.
The Shulchan Arukh’s opinion is somewhat unclear. In Hilkhot Eiruvin (378:3, 409:7), he rules in accordance with the Rambam that 18 grogerot are equivalent to 6 eggs, which means that a ke-zayit must be smaller than a third of an egg. However, regarding the laws of matza (486), he writes: “Regarding the size of a ke-zayit, some say (yesh omrim) that it is half of an egg.”
The Acharonim note this apparent contradiction, as well as the phrase “some say” in the context of matza. Some (see, for example, Mishna Berura 486:1 and R. Chaim Naeh, Shiurei Torah, p. 190, n. 24) suggest that the Rambam is strict regarding mitzvot de-oraita (Biblical mitzvot), such as matza, and most probably a berakha acharona as well, due to the principle of safek berakhot le-hakel. Others (see R. Chaim Benish, “Shiur Ke-Zayit – Bi’ur Da’at Rishonim Ve-Acharonim,” who cites numerous Acharonim) suggest that the Shulchan Arukh did not intend to rule against the Rambam and the prevalent custom, but rather merely to cite the only explicit shiur that appears in the Rishonim.
If the size of a ke-zayit is to be measured in relation to an egg, according to the Ri, as cited in the Shulchan Arukh, then what is the proper measurement of an egg? The Acharonim offer a number of approaches. The most prominent is suggested by R. Chaim Naeh.
In 1943, R. Chaim Naeh (1890–1954), author of the Ketzot He-Shulchan, published “Shi’urei Torah,” which defended the measurements used for generations by the community in Jerusalem. He based some of his measurements upon a passage in the Rambam (Peirush Ha-Mishna, Eduyot 1:2) in which he reports that the measurement of a revi’it of water is equivalent to 27 Arabic coins known as “drahms.” Since a revi’it is the equivalent of an egg and a half (including its shell), an egg’s volume in displaced water is 18 drahm. R. Chaim Naeh measured a drahm, which was used as a coin in the Arab world for hundreds of years, and reported that each drahm was 3.205 gram. Thus, 18 drahm are 57.6 gram, and the volume of an egg with its shell is approximately 57.6 cc.
R. Chaim Naeh further estimates that according to Tosafot, who maintain that a ke-zayit is a half of a ke-beitza, half of a ke-beitza without its shell (54.7 cc) is 27 cc. According to the Rambam, a ke-zayit is a third of an egg, with or without its shell, 19.2 cc or 17.3 cc accordingly.
Interestingly, recent research has determined that the drahm used by the Rambam was actually smaller than the one measured by R. Chaim Naeh, 2.83 gram (see Yaakov Gershon Weiss, Sefer Midot U-Mishkalot Shel Torah, p. 89). Accordingly, R. Chaim Pinchas Benish (Midot Ve-Shiurei Torah, pp. 69, 71) claims that the volume of an egg according to the Rambam is actually 50 cc., and the measurements of a ke-zayit are less than 17 cc (Rambam) and 25 cc (Tosafot). He records that both R. Shlomo Zalman Auerbach and R. Ovadia Yosef accepted this revised shiur.
Have Eggs Doubled in Size?
Interestingly, R. Yechezkel Landau (1713 –1793), author of the Noda Be-Yehuda, questioned the commonly accepted size of an egg. Based upon another method of measuring that appears in the Talmud (Pesachim 109a-b), R. Landau discovered a discrepancy between the measurements based on volume and the measurements based on dimensions. (This discrepancy was actually noted earlier by the Tashbetz 3:33 and others.) He writes (Tzalch, Pesachim 116b):
For in truth it is clear in the Shulchan Arukh (486) that the size of a ke-zayit is half the size of an egg. However, it is clear to me by way of measurement that with the eggs that we have in our day, a whole egg of our day is only half the size of an egg that was used for the Torah quantities… And against our will we see that things have changed in our time; either thumbs have grown, and they are bigger than the thumbs of the days of the Tanna’im, or the eggs have shrunk and in our day they are smaller than the eggs of the era of the Tanna’im. And it is known that the generations progressively decline, and it is therefore impossible that our thumbs should be larger than the thumbs in the day of the Sages of the Mishna.
R. Landau maintains that one must attribute this discrepancy to thumbs becoming larger over time or to eggs becoming smaller than they once were. He concludes that today’s eggs are smaller than in the past:
It is therefore necessarily the case that the eggs of our day are smaller… and since it has become clear that our eggs are smaller by half, therefore the size of a ke-zayit, which is [originally] half an egg, is as the size of a whole egg of today. And thus I evaluate the eating of matza and maror…
R. Eliezer Fleckless (1754 – 1826), a student of the Noda Be-Yehuda and author of the Teshuva Me-Ahava, reports that when he suggested that his teacher arrived at this conclusion because he himself was an especially tall person, R. Landau “shook his head and was quiet.” Some (see Yehuda Ya’aleh YD 205) suggest that this indicates that the Noda Be-Yehuda actually changed his mind!
In 1947, R. Avraham Yeshayahu Karelitz (1878–1953), known as the Chazon Ish, published a response to R. Chaim Naeh’s Shiurei Ha-Torah in which he defended the position of the Noda Be-Yehuda. In his Kuntras Ha-Shiurim (OC 39), he concludes that since the volume of a ke-beitza is 100 cc, according to Tosafot, a ke-zayit is 47.5 cc (1/2 of an egg without its shell) and according to the Rambam, it is 33 ml (1/3 of an egg with its shell).
The Acharonim and recent scholars have raised many objections to the view of the Noda Be-Yehuda and the Chazon Ish.
Some Acharonim raise textual objections to the notion that the size of the ke-zayit and ke-beitza are double the currents sizes. For example, the Mishna Berura (Bi’ur Halakha 271, s.v. revi’it) notes that based on the gemara (Yoma 80a), a person’s two cheeks (melo lugmav) can hold a revi’it, approximately the volume of 1.5 eggs. According to the Noda Be-Yehuda, a person’s mouth should be able to hold the equivalent of three eggs (150 cc), which seems virtually impossible.
Others object on different grounds. R. Natan Slifkin, in an essay supporting the minimalist view of the ke-zayit, summarizes much of the scientific and archeological evidence. For example, he cites Professor Yehuda Feliks (Kelai Zera’im Ve-Harkavah, p. 184 n. 5.), who relates that the eggs that were preserved whole in the volcanic destruction of Pompeii two thousand years ago were “around the size of the small Arab eggs of our time,” which he defines as 41.4cc. Furthermore, he notes that olive pits found in archeological digs from the time of the Mishna are no larger than olives found today (see Mordechai Kislev, “Kezayit – Peri Ha-Zayit Ke-Midat Nefach,” Techumin 10, pp. 427-437).
Although halakhic charts often cite the stringent opinion of the Chazon Ish and list a ke-zayit as either 33 cc or almost 50 cc, as they appear in his Kuntrus Shiurim (OC 39:17), some sources indicate that the Chazon Ish himself believed that these measurements are chumrot (stringencies) and are not halakhically required. R. Hadar Yehuda Margolin, in one of his many enlightening articles on this topic (“Berur Shitat Ha-Chazon Ish Be-Shi’ur Kezayit,” Moriya 107), insists that the Chazon Ish – based on his own letters (Iggerot 194) and testimony from his nephew, R. Chaim Kanievsky – maintained that me-ikkar ha-din, we do not assume that the size of an olive has changed, and one may assume that a third of an egg (17 cc) is sufficient for matza and for a berakha acharona.
Some suggest following the stringent view of the Noda Be-Yehuda (and Chazon Ish) when fulfilling the Biblical mitzva of matza (see Mishna Berura 486:1), and possibly even Kiddush (which is based on the Biblical obligation of “zakhor”). However, most Acharonim reject this opinion, and the common practice in Europe before WWII was certainly not to follow this view (see, for example, Mishneh Halakhot 8:194).
Ke-Zayit is the Size of an Olive
The second approach to assessing the size of a ke-zayit maintains that there is no inherent relationship between the size of an olive and an egg. Indeed, even the Rambam cited above never mentions the size of a ke-zayit; he merely implies that a ke-zayit is smaller than a fig, which is a third of the size of an egg. Many early authorities maintained that a ke-zayit was in fact a ke-zayit, i.e. the size of an olive.
Some cite proofs from the Talmud that seem to reject the larger amounts suggested by R. Chaim Naeh, and certainly those of the Chazon Ish.
For example, the gemara (Menachot 26a; see Rambam, Hilkhot Ma’aseh Ha-Korbanot 13:14) implies that a kohen must be able to fit the volume of two olives into his hand (ein kometz pachot mi-sheni zeitim). It is impossible to fit within the cavity of three fingers and the palm (kemitza) even two thirds of an egg, let alone an entire one.
Similarly, as mentioned above, the Talmud (Keritut 14a) asserts that the esophagus can hold the volume of two eggs. Here too, it seems unlikely that one can swallow a half and egg, or even a third of an egg, at once.
In addition, the gemara (Berakhot 37a) describes a case in which there are perurim (crumbs) the size of a ke-zayit. If a ke-zayit were the size of a third or half of an egg, they would certainly not be called crumbs!
Finally, the gemara (Makot 16b) describes a situation in which one eats 2-3 large ants or 10 small ants that equal the size of a ke-zayit. It seems unlikely that the Talmud refers to ants so large that only 2-4 would equal the size of a third or half of an egg.
Aside from the proofs from the Talmud and the implicit agreement of most Rishonim that a ke-zayit is smaller than a fig, numerous Geonim and Rishonim also explicitly support the claim that a ke-zayit is not measured in relation to an egg and is indeed the size of an olive.
For example, R. Sherira Gaon (c.900-c.1000), in a recently discovered responsum (cited in Sefer Ha-Eshkol, vol. II, Hilkhot Challa 13, p. 52), insists that the measurements of eggs and olives are not based upon the weight of coins, but rather upon the size of the egg and olive itself:
You asked me to explain if there is a weight given for the fig, olive, date and other measurements in the weight of Arabic coins, and you explained that R. Hilai Gaon clarified that the weight of an egg is 16 2/3 silver pieces. [You wondered,] if the others do not have an ascribed weight, why is the egg given one? It is known that these other measurements are not given any equivalent weight in silver, not in the Mishnah nor the Talmud. If [the Sages] had wished to give a measurement in terms of the weight in dinarim, they would have done so originally. Rather, they give the measurements in terms of grains and fruit, which are always available, and one is not to say that they have changed…
We practice according to the Mishna: Everything goes according to the observer… And likewise with regard to the olive and date, it is explained in this Mishna that it is not referring to a large one or a small one, but rather an average one – and it is also according to the view of the observer.
Similarly, Rav Hai Gaon (939-1038), writes:
And therefore the Torah gave measurements in terms of eggs and fruits … because eggs and fruit are found in every place. For it is known and revealed before the One Who spoke and brought the universe into existence that Israel is destined to be scattered amongst the nations, and that the weights and measures that were in the days of Moses and that which were added to in the Land of Israel would not be preserved, and that the measurements change in different times and places… Therefore, the Sages related the quantities to fruit and eggs, which always exist and never change. They made the quantity of an egg depend upon the view of the observer. (Ibid., pp. 56-57)
The Rashba (Mishmeret Ha-Bayit, p. 96) and the Ritva (Shabbat 76b, printed at the back of the Mosad HaRav Kook edition) also explicitly speak of a ke-zayit much smaller than a third of an egg.
In addition, numerous Acharonim also reportedly maintain that a ke-zayit is indeed the size of an olive, including R. Chaim Volozhin (Sha’arei Rachamim 51, Minhagei Ha-Grach) and R. Avraham Bornstein (the Avnei Nezer, cited in Midot Ve-Shiurei Torah, p. 510).
Which olives are we to measure against? The Mishna (Keilim 17:8) teaches: “The ke-zayit of which they spoke is neither a large one nor a small one, but rather a medium-sized one, which is the egori.” Prof. Mordechai E. Kislev (“Peri Ha-Zayit Ke-Midat Nefach”) describes three olives common to the land of Israel: the Shami (a large olive, approximately 12-13 cc), the Melisi (a small olive, 0.5-1cc), and the Suri or Nabali olives, which range from 2.5- 6 cc). The average olive found in Israeli measures between 3–4 cc. R. Chaim Benish (“Shiur Ke-Zayit – Bi’ur Da’at Rishonim Ve-Acharonim”) suggests that one should be stringent and assume that a ke-zayit is no smaller than the larger olives found in Israel, which measure close to 7.5 cc.
Shiur Ke-Zayit- Summary and Conclusion
Most authorities adopt the view of R. Chaim Naeh and assume that a ke-zayit is approximately 27 cc (half of a ke-beitza). The more accurate calculation of the Egyptian drahm leads to a slightly smaller amount. Many halakhic compendiums write that one should measure a portion of food against a standard match box, approximately 25-30 cc (5X3.5X1.5); a plastic bottle-cap is approximately 10 cc. Some (including R. Kanievsky, as cited above) assume that one can rely upon the Rambam’s view and say a berakha acharona after eating at least a third of a ke-beitza, at least 17 cc.. Others follow the tradition of R. Chaim Volozhin and others and say a berakha akharona after eating an amount equivalent to the volume of an olive, around 3–4 cc.
Volume or Weight
The Talmud in numerous places implies that the volume (nefach), and not the weight (mishkal), is the determining factor in measuring shiurim. For example, the gemara (Pesachim 109a-b) defines the liquid measure of a revi’it, which is equivalent to an egg and a half, as 2 fingerbreadths X 2 fingerbreadths X 2.7 fingerbreadths. Similarly, the mishna (Uktzin 2:8), which we will return to shortly, teaches: “An airy loaf is evaluated as it is. If there is a hollow inside, it is compressed.” Finally, the Tosefta (Nazir 4:1) describes how one places a ke-zayit aguri in wine and drinks the displaced wine, clearly indicating that a ke-zayit is measured by volume and not weight (see Rashi, Chullin 108b, s.v. chalav).
The Geonim also clearly believed that a ke-zayit was measured by volume. They write (Teshuvot Ha-Geonim, Harkavy 268):
And if you were to suggest [that they be measured by] weight, the Rabbis did not specify weight and Ha-Kadosh Barukh Hu did not exact with us in weight; [rather,] every person who estimates according to his evaluation has fulfilled his obligation
The Geonim note that it is virtually impossible for every person to know the measurement of every food. Rather, a person is to estimate according to size.
The Rambam (Commentary to the Mishna, Challah 2:6; Hilkhot Chametz U-Matza 5:12) also clearly rejects measuring shiurim by weight. The Maggid Mishna (ibid.) explains that the weight is not always similar to the volume, and therefore the shiurim clearly refer to volume and not weight.
The Shulchan Arukh (456:1) cites the Tur, who describes determining the shiur of challa thought the displacement of water. Furthermore, the Rema (486:1) implies regarding the shiur of maror that one estimates the proper shiur based upon volume.
Interestingly, R. Yaakov Chaim Sofer (1870–1939), in his Kaf Ha-Chaim (Orach Chayim 168:45-46), asserts that “it is unlikely that it is dependent upon the evaluation of each person, as he sees it.” After citing a number of Sephardic authorities, he concludes: “It is not the common custom among halakhic authorities to estimate all measurements, such as a ke-zayit of matza on Pesach, and a ke-zayit of maror, and a ke-zayit for the measurement of a berakha acharona … by weight… and this should not be changed.” Numerous Sephardic authorities rule that a ke-zayit is measured by weight, such as the equivalent of 27 grams, although they assume that weight is only used as a means of properly determining the volume equivalent of a ke-zayit, as weight and volume are generally similar. Other Sephardic authorities (Ohr Le-Tzion, vol. 2 ch. 14, n. 17; Yalkut Shemesh 137; see also Machzikei Berakha 486:2) disagree and insist that one measure the size of a ke-zayit based upon nefach.
Assuming that one measures a ke-zayit according to a food’s volume, does it matter if a food is light or dense? Does one include air pockets in the measurement of a ke-zayit?
As mentioned above, the mishna (Uktzin 2:8) teaches: “An airy loaf is evaluated as it is. If there is a hollow inside, it is compressed.” This mishna implies that while the food should be compressed if there is an air pocket,, generally speaking, we do not take the density of a food into consideration.
Most Acharonim assume that if a food is naturally light or fluffy (bread, popcorn, etc.), one still measures by its volume (see Mishna Berura 186:3). R. Ben Zion Abba Shaul, in his Ohr Le-Tzion (ibid.), rules that airy or fluffy foods should always be condensed.
What if a food absorbed water after it was prepared, and then expanded? Does it matter if the food was originally that large and subsequently shrunk (i.e. raisins) and became enlarged again or if it was always small and simply expanded?
The Rambam (Hilkhot Ma’akhalot Asurot 14:5) writes:
The Rambam clearly believes that a ke-zayit is determined by its current size. However, he adds:
If afterwards one left it in the rain and it expanded, one is liable for either karet or lashes. If originally it was smaller than an olive-sized portion and then expanded to the size of an olive, it is forbidden to partake of it, but one is not liable for lashes for it.
Here, he indicates that if a food returns to its original size (i.e. such as raisins soaked in water), then we follow the current volume. If, however, the food absorbed water and grew to a larger, unnatural volume, we follow the original size.
Indeed, this appears to be the ruling of R. Yishmael ben Avraham Yitzchak Ha-Kohen (Italy, d. 1811) in his Zera Ha-Emet (29). Similarly, the Mishna Berura (210:1) rules:
If there is an airy loaf that expanded until the air pocket are no longer noticeable, one who eats a ke-zayit of it does not say a berakha acharona, because in truth, he did not eat a ke-zayit. Similarly, if there was a ke-zayit and it depressed and became smaller, one does not say a berakha [acharona] over it unless it becomes bigger again.
The Mishna Berura refers here to bread that after baking expanded even more. Elsewhere (486:3 and Sha’ar Ha-Tziun 7), he rules that regarding matza, if its air pockets are not noticeable, there is no need to compress them.
Volume or Weight - Summary
The mishna, Rishonim, and most Acharonim clearly rule that one should estimate the size of a ke-zayit based upon volume (nefach). Volume includes natural pockets of air, which are not noticeable. If they are noticeable, the food should be condensed in order to determine its volume. Some Sephardic authorities maintain that one should measure according to weight, as it is often difficult to assess the size of a piece of food.
R. Eliezer Melamed writes in his Peninei Halakha (Berakhot, pg. 217):
Every person should learn to evaluate the volume of foods in relation to half an egg… And we already learned that a person does not have to be overly concerned, as the Rabbis assigned each person the authority to estimate the measurement itself, despite the probability that a person may err a bit above or below.
Although we noted above that many assume that the measurement is less than a third of an egg and others even measure against an olive itself (4 -6 cc), his sentiment is still worth considering.
Shiur of Time for a Berakha Acharona - Kedei Akhilat Peras
The Talmud teaches in numerous contexts that in order to violate certain prohibitions or in order to fulfill certain mitzvot that require “akhila” (eating), one must eat a specific amount (shi’ur), most often a ke-zayit (the size of an olive), in a certain amount of time. This amount of time is generally referred to “kedei akhilat peras,” the amount of time it takes to eat half a loaf of bread. This amount of time is relevant in the context of eating prohibited foods (see Keritut 12b), as well as when fulfilling mitzvot, such as matza (Berakhot 37b) and marror (Pesachim 114b). This amount of time is also relevant in the context of eating of Yom Kippur as well (see Tosefta, Yoma 4:3), although the shi’ur of eating on Yom Kippur is a ka-kotevet (the size of a date).
Interestingly, the Acharonim (see, for example, Magen Avraham 210:1, Panim Me’irot 2:27) question whether this shi’ur should apply to Birkat Ha-Mazon. Some suggest that since Birkat Ha-Mazon is dependent upon “satisfaction” (sevi’a), as the verse states, “When you have eaten and are satisfied, you shall bless the Lord your God for the good land which He has given you” (Devarim 8:10), and not “eating,” even one who eats the minimum amount over a longer period than kedei akhilat peras should be required to say Birkat Ha-Mazon. This is not the accepted view.
The Acharonim (Magen Avraham, ibid.) assume that in order to be obligated to say a berakha acharona, one must eat a ke-zayit of food within kedei akhilat peras. How much time is “the time it takes to eat a half a loaf of bread”?
The Rishonim, based upon a different opinions among the Tanna’im (see Eiruvin 82b), debate the size of a peras. In various contexts, the Rambam (Hilkhot Eiruvin 1:9; Shevitat He-Asor 2:4; Ma’akhalot Asurot 14:8, etc.) rules that a loaf is the size of six eggs; thus, half a loaf, a peras, is the size of 3 eggs (3 ke-beitzim). One must therefore eat a ke-zayit in the time period it takes to eat 3 ke-beitzim. Rashi (Pesachim 44a) disagrees and rules that a loaf is the equivalent of 8 eggs, and a peras is therefore the size of 4 eggs (4 ke-beitzim). Accordingly, one has somewhat longer to eat the ke-zayit – the time it takes to eat 4 ke-beitzim.
The Shulchan Arukh (OC 378:3, 612:4) cites both views. Some (Shulchan Arukh Ha-Rav 612:4, cited by Mishna Berura 412:8) suggest adopting the more stringent approach regarding laws of Biblical origin. Similarly, due to the principle of safek berakhot le-hakel, one should adopt the shorter measurement regarding berakha acharona and only recite the blessing if he completed the ke-zayit in the shorter amount of time.
The Acharonim offer different estimates for the time it takes to consume a peras. The Chatam Sofer (6:16), for example, suggests that this may be as long as nine minutes. The Sedei Chemed (Asifat Dinim, Akhila 3) cites opinions that maintain that kedei akhilat peras is eight minutes. The Bikurei Ya’akov (639:13) writes that kedei akhilat peras is an eighth of an hour, or 7 ½ minutes. Arukh Ha-Shulchan (202:8) estimates this time to be between three to four minutes. The Kaf Ha-Chaim (210:8) rules that kedei akhilat peras is 4 minutes. (Interestingly, the Minchat Chinukh [313:5] objects to determining set measurements of time, as each food must be estimated separately.)
Regarding eating matza,R. Ovadia Yosef (Yechave Da’at) rules that one should preferably follow the view of four minutes. R. Moshe Feinstein (Iggerot Moshe, OC 4:41) accepts the views of the Marcheshet (1:14:8), who estimates kedei akhilat peras to be about three minutes.
Given that most Posekim accept a smaller measurement of a ke-zayit, ranging from 3-4 cc – 17 cc, it is generally not difficult to consume a ke-zayit of food within a few minutes, and to thus become obligated in a berakha acharona.
Of course, while reliance on the longer measure is a leniency regarding berakha acharona, regarding eating on Yom Kippur, it is relied on as a stringency. A choleh (sick person) is often instructed to eat or drink small amounts, known as “shi’urim,” in the course of a kedei akhilat peras. Many will insist that a choleh should wait up to nine minutes between shi’urim, in accordance with the Chatam Sofer cited above. Others adopt more lenient opinions, and one who must eat should thus consult with a halakhic authority before Yom Kippur.
The Shiur of Liquids for a Berakha Acharona
The discussion above revolved around the amount of food over which one says a berakha acharona. What about liquids? How much must one drink in order to become obligated to a say a berakha acharona, and in how much time?
The Rishonim debate whether the shi’ur for liquids is the same as the shi’ur for food, i.e. a ke-zayit. Tosafot (Berakhot 39a and Yoma 79a) suggest that the shi’ur may be the same as for food, a ke-zayit. The Rambam (Hilkhot Berakhot 1:2) rules that one only says a Borei Nefashot after drinking a revi’it, which is the amount of liquid displaced by one and a half eggs. The Rosh (Berakhot 6:24), and subsequently the Shulchan Arukh (210:1), cites both views, and rules that one should preferably drink less than a ke-zayit or more than a revi’it in order to avoid a situation of doubt. It is customary to say a berakha acharona only after drinking a revi’it of liquid.
As we discussed previously, the Acharonim discuss the size of an egg, and accordingly, the volume of a revi’it (1.5 eggs). R. Chaim Naeh ruled that a revi’it is 86 cc (“kos” in gematria). Although the Noda Be-Yehuda, and subsequently the Chazon Ish, maintain that our eggs are smaller than the eggs of the ancient world, and a revi’it therefore should be measured as 150 cc (“kos hagun” in gematria), the accepted practice is in accordance with R. Chaim Naeh. Some suggest, based upon recent discoveries, that the size of a revi’it is actually 75 cc.
Within how much time must one drink a revi’it of liquid in order to become obligated to say a berakha acharona?
The Rambam writes concerning prohibited foods (Hilkhot Shevitat He-Asor 2:4; Hilkhot Ma’akhalot Asurot 14:9; Hilkhot Terumot 10:3) that regarding liquids, the shi’ur for being considered an act of drinking is “kedei sheti’at revi’it,” the amount it time in which one ordinarily drinks a revi’it of liquid. The Ra’avad (Hilkhot Terumot, ibid.) disagrees and rules that the shi’ur of kedei achilat peras applies to liquids as well. The Shulchan Arukh (212:10) rules in accordance with the Rambam. The Vilna Gaon rules in accordance with the Ra’avad.
The Magen Avraham (210:1) assumes that this debate applies to a berakha acharona as well. The Sha’ar Ha-Tziyun (210:11) explains that “kedei sheti’at revi’it” refers to “the manner in which people drink … in two sips.” R. Moshe Feinstein (Hagadat Kol Dodi, 3) adds that even one who drinks a revi’it in many sips, as long as he does not interrupt. Therefore, some Posekim note that one generally should not say a blessing after eating a bowl of soup, as a revi’it is not consumed within a few sips. Interestingly, other Acharonim suggest that even the Rambam would adopt the longer shi’ur regarding a berakha acharona, as the berakha acharona relates not just to the act of eating, but the hana’ah (benefit) as well.
Should we distinguish between different types of liquids, which are consumed in different ways? For example, some Acharonin (see Taz 210:1 and 190:1) suggest that after drinking even a small amount of alcohol (scotch, vodka, etc.), one should say a berakha acharona. They explain that the shi’ur of revi’it should not apply to drinks that one ordinarily drinks in small amounts. Similarly, some Acharonim (see Maharsham 1:175) permit one to say the daytime Kiddush on less than a revi’it of liquor for this reason. The Acharonim (see, for example, Magen Avraham 194:4, Mishna Berura 190:14) reject this rationale and insist that one only says a berakha acharona after drinking a revi’it, regardless of the type of liquid.
Similarly, some suggest that the rules regarding hot beverages, such as tea and coffee, should be different. Some (see, for example, Ginat Veradim, OC 1:17) maintain that since it is customary to drink them slower, and this is the “derekh hana’ato”, even one who drank a revi’it of tea in more than kedei sheti’at revi’it should say the berakha acharona. Others suggest the opposite – liquids that one generally drinks slowly are completely exempt from a berakha acharona (see Sha’arei Teshuva 204:12; see also Birkei Yosef 204:6 and Yabi’a Omer 5:18:5), as this is not the normal manner of drinking.
R. Ovadia Yosef (Yabi’a Omer, OC 5:18) analyzes this issue in great depth and concludes that the custom if Sephardim is not to say a berakha acharona after drinking hot beverages unless one drinks a revi’it after it has cooled off (see below). On the other hand, R. Dovid Z. Hoffman, in his Melamed Le-Ho’il (OC 1:25), relates that his custom, as well as the custom of the Sho’el U-Meshiv and the Minchat Chinukh, was to say a blessing after drinking hot beverages. Similarly, the Maharam Shik (OC 85) records that this is his custom as well. The Shemirat Shabbat Ke-Hilkhata (vol. 2, ch. 44, n. 96) relates that this was also the practice of many great rabbis, including R. Shlomo Zalman Auerbach.
Interestingly, R. Yedael Meltzer (Sefer Etz Ha-Chaim pg. 399, cited by R. Efraim Greenblatt in his Rivevot Efraim OC 5:166) relates that his grandfather, R. Isser Zalman Meltzer (1870 – 1953), the author of the Even Ha-Ezel, was accustomed not to say a berakha acharona after drinking coffee, in accordance with the ruling of the Mishna Berura (see below). However, once R. Shlomo Zalman Auerbach visited R. Meltzer, and noticed that he said the berakha acharona after drinking coffee. R. Auerbach, who was familiar with R. Meltzer’s practice, questioned the change in his custom. R. Meltzer responded that a few days earlier, R. Yitzchak Ze’ev Soloveitchik (1886 - 1959) had visited, and he noticed that he said a berakha acharona after drinking coffee, and explained that this was in accordance with the practice of his father, R. Chaim Soloveitchik. R. Meltzer, himself a student of R. Soloveitchik in the Volozhin yeshiva, decided to change his practice. In turn, R. Shlomo Zalman Auerbach, impressed that R. Meltzer, even in his later years, would change his practice, also changed his custom, and began to say a beracha acharona after drinking coffee. R. Moshe Shternbuch (b. 1926), in his Teshuvot Ve-Hanhagot (2:135) also records that his teacher, R. Yitzchak Ze’ev Soloveitchik, would say a berakha acharona after drinking tea within the time of kedei akhilat peras.
The Mishna Berura (210:1) suggests that one should leave a revi’it of coffee or tea until it cools off and then drink a revi’it, in order to become obligated in the berakaha acharona according to (almost) all opinions.
Definition of Foods and Liquids
There are some foods whose status is in doubt, and it is therefore unclear whether they should be treated as solids or liquids with regard to a berakha acharona.
For example, should we view ice-cream as a solid, in which case one says a berakha acharona after eating a ke-zayit within the time of kedei akhilat peras? Or is it a liquid? In that case, it would be unlikely that one would be obligated to recite a bracha achrona, as it is uncommon toeat a revi’it of ice-cream within the time it generally takes to drink a revi’it. In addition, as we learned previously, the blessing Borei Peri Ha-Gefen (when one drinks wine as well) exempts other beverages. Must one say a blessing before eating ice-cream after saying Kiddush (and drinking wine) on Shabbat morning?
The Shulchan Arukh (208:6) rules that a “daysa” (soft, grain-based cereal) that is fluid enough to be drunk is viewed as a liquid; if it is thick enough to be chewed, it is treated as a solid. Similarly, the Shulchan Arukh Ha-Rav (Seder Birkat Ha-Nehenin 8:8) writes: “Food which has melted to the extent that it is fit for drinking is not longer considered to be food. So too a liquid which solidifies and can be eaten is no longer considered to be a liquid.” (See also Ve-Zot Ha-Berakha, pg. 44 and pg. 100).
Based on this distinction, ice-cream, jelly, pudding, and soft cheeses (cottage cheese) would certainly be viewed as solids. More viscous dairy products would be viewed as liquids. R. Ovadia Yosef (Yabi’a Omer OC 8:25) disagrees and maintains that these foods should be viewed as liquids, regarding the laws of berakhot.
Tziruf – A Berakha Acharona after Eating Different Foods
Different foods upon which the same berakha rishona is recited combine to the shi’ur of a ke-zayit. Therefore, if one eats half of a ke-zayit of an apple, and another half of a ke-zayit of an orange, one says Borei Nefashot afterwards. Similarly, if one eats half a ke-zayit of a fruit of the seven species and another half of a ke-zayit of another fruit of vegetable, one says Borei Nefashot (Mishna Berura 210:1). Liquids and solids do not combine to reach a shi’ur.
We learned in previous shiurim that when eating two foods, one says the blessing over the ikkar (the more important, primary food), which exempts the tafel (the secondary food). Similarly, a berakha acharona is said only over the primary food, assuming that one ate a ke-zayit (Shulchan Arukh 210:1; see Mishna Berura 210:1 as well).
The Acharonim discuss how to view a cake, the majority of the ingredients of which are usually egg, oil, and sugar, and not flour. Must one say a berakha acharona after eating a ke-zayit of cake or after eating a ke-zayit of flour?
The Magen Avraham (208:15; see also Derisha 208:1) maintains that one who eats a ke-zayit of cake or cookies, even if he does not eat a ke-zayit of flour, says the blessing of Al Ha-Michya. This seems to be the opinion of most Rishonim (see, for example, Rif, Berakhot 37b; Rambam, Hilkhot Berakhot 3:11-12; Rosh, Berakhot 6:7, et al.), who do not mention that one must eat a ke-zayit of flour. The Chayei Adam (50:21) records that this is the popular custom. The Mishna Berura 208:48) cites this as well, although he concludes that preferably one should only say a berakha acharona after estimating that he ate a ke-zayit of flour.
R. Moshe Feinstein (Iggerot Moshe, OC 1:71; see also Minchat Yitzchak 9:15 and Teshuvot Ve-Hanhagot 2:132) disagrees and expresses his amazement at the custom cited by the Mishna Berura. He insists that one should only say the Al Ha-Michya after eating an amount of cake which contains a ke-zayit of flour. Although, as mentioned, the custom seems to be in accordance with the first view, many suggest being stringent and eating a ke-zayit of flour. While hard, yeast cakes are generally mostly flour, in some softer cakes, flour may only be a ¼ or even less of the ingredients. As we mentioned previously, many maintain that a ke-zayit is indeed the size of an actual olive (i.e. 3-4 cc), in which case it would not be difficult to consume this quantity of flour, even according to the stricter opinion.
One must say a separate blessing on fruit, cheese, and other fillings, and they do not combine with the flour to equal a ke-zayit. Therefore, at times one may eat a very small piece of cake with a ke-zayit of filling and say only a Borei Nefashot.
The blessing of Borei Nefashot is said after drinking (except wine) and eating rice, meat, fruits (not of the seven species), and vegetables.
Most Acharonim (see, for example, Shulchan Arukh 202:11 and Mishna Berura 202:55) maintain that unlike the berakha rishona of She-Hakol, Borei Nefashot is not a “general” blessing and cannot be said after eating foods which require a different blessing, such as Birkat Ha-Mazon or Me’ein Shalosh (Al Ha-Michya, Peirot,and Gefen). Some (see Kaf Ha-Chaim 202:79) maintain that be-di’avad, one who says Borei Nefashot after even a food that requires the Berakha Me’ien Shalosh fulfills his obligation. Furthermore, R. Moshe Feinstein (Iggerot Moshe, OC 1:74) suggests that if one does not have a siddur and does not know the Berakha Me’ein Shalosh by heart, he should say Borei Nefashot instead.
R. Ovadia Yosef (Yechaveh Da’at 2:22) disagrees and insists that Borei Nefashot is not a general blessing that exempts from other blessings, even in extenuating circumstances. Indeed, he takes this opportunity to implore us to know blessings by heart so that one does not find himself unable to say a blessing because he does not have a siddur.
Al Ha-Michya and Al Ha-Gefen
If one ate a ke-zayit of mezonot but is unsure whether he drank a revi’it of wine or if he ate a ke-zayit of fruit from the seven species, since he is already obligated to say Al Ha-Michya, he should mention wine (Al Ha-Gefen) or the fruits (Al Ha-Peirot) as well (Taz 208:19).
Furthermore, if one ate a ke-zayit of fruits from the seven species and a ke-zayit of other fruits, the blessing of “Al Ha-Peirot” suffices, as he mentions “fruits” in the blessing. If, however, he ate vegetables, he must say a Borei Nefashot as well (Shulchan Arukh 208:13). The Mishna Berura (208:64) notes that some Acharonim disagree and maintain that the blessing of Al Ha-Peirot covers the vegetables as well. Therefore, he suggests that one say the Borei Nefashot first, lest the blessing of Al Ha-Peirot cover both the fruit and the vegetables.
The Sha’arei Teshuva (208:9) cites Acharonim who maintain that although one should preferably say Borei Nefashot after eating rice, if one said Al Ha-Michya, or if one ate other cookies or crackers with the rice and said Al Ha-Michya, the rice is exempted. Some Acharonim (Kaf Ha-Chaim 208:41; Ben Ish Chai, Pinchas 18) maintain that even le-khatchila, one should say only one blessing. This is also the view of R. Ovadia Yosef (Yalkut Yosef 208:12). Others (see Shevet Ha-Levi 9:65) insist that the even the opinions cited by the Sha’arei Teshuva are somewhat novel, and surely le-khatchila one should say both blessings.
Just as the blessing Borei Peri Ha-Gefen exempts other drinks, the blessing of Al Ha-Gefen exempts not only the wine, but other beverages as well (Shulchan Arukh 208:15).
Waiting Before the Berakha Acharona
The mishna (Berakhot 51b) teaches that one may say the berakha acharona “until the food in his stomach has been digested.” The Talmud (ibid. 53b) explains that this is “as long as he is not hungry.” The Mishna Berura (184:20) records that some Acharonim estimate this to be about 72 minutes after one finishes eating. Seemingly, this should depend on the specific food and person. If one feels satiated even after 72 minutes have passed, one may still say the blessing. The Acharonim write that when in doubt, a person, it is proper to eat another ke-zayit of food in order to be obligated to say the berakha acharona.
 In recent years, of number of articles have been written on this topic. These articles were invaluable in producing this summary. See, for example: Beinish, Chaim, “Shiur Ke-Zayit: Midot Ve-Shiurei Torah” (Bnei Berak, 1990); Benish, Chaim, “Shiur Ke-zayit – Bi’ur Da’at Rishonim Ve-Acharonim,” in Kovetz Beit Aharon Ve-Yisrael 2; Greenfield, Avraham, “Ha-Kesher Bein Shiurei Ke-zayit Ve-Ke-Beitza,” Techumin 14 (1994); Kislev, Mordechai, “Ke-zayit – Peri Ha-Zayit Ke-Midat Nefach,” Techumin 10 (1989); Margolin, Hadar Yehuda, “Beirur Shitat Ha-Chazon Ish Be-Shiur Ke-zayit,” Moriya 107 (1993); Margolin, Hadar Yehuda, Kuntras Shiur Ha-Kezyit (taken from Hidurei Ha-Midot); Navon, Hayim, “Kama Zeitim Yesh Be-Ke-zayit,” Alon Shevut Bogrim 18 (2003); Slifkin, Natan, “The Evolution of the Olive” (2010). See also Mandelbaum, Alexander, Ve-Zot Ha-Berakha (1992); Melamed, Eliezer, Peninei Halakha – Berakhot (2009).