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The Shiur of Ke-Zayit for Berakha Acharona

  • Rav Moshe Taragin


            The gemara in Berakhot (38b) discusses the necessary shiur for berakhot.  After relating the story of R. Yochanan who recited a berakha acharona upon a salted olive, the gemara queries:  Since by removing the pit the shiur was diminished, why did R. Yochanan recite the berakha?  After all, the shiur of food necessary to recite a berakha acharona is the quantity equivalent to the size of an olive (literally a ke-zayit!) and without the pit R. Yochanan's food was necessarily less than that!  The gemara responds that the olive in question was a extraordinarily large one so that its mass, even sans the pit, was the equivalent of a standard sized olive.  What emerges from this gemara is that no berakha acharona is to be recited if less than a ke-zayit of food is consumed.


            Rashi in Berakhot explains the need for a ke-zayit based upon the syntax of the pasuk "ve-akhalta ve-sava'ta u-veirakhta" (Devarim 8:10), from which we derive the laws of birkat ha-mazon and berakha achat me-ein shalosh (known commonly as al hamichya)).  This pasuk, actually, employs the term "VE-AKHALTA" which connotes a formal act of eating.  According to Rashi, a berakha acharona may only be recited subsequent to the performance of a ma'aseh akhila (act of eating); if less than a ke-zayit is consumed, no halakhic act of eating has been performed.


            Alternatively, one might have adopted a slightly different basis for this halakha.  One might not require a formal act of eating to justify a berakha acharona.  Merely deriving pleasure from a quantity of food warrants the recitation of  this berakha.  However, halakha doesn't recognize less than a ke-zayit of food as a SIGNIFICANT mass.  Though an ACT is not necessary to warrant a berakha acharona, a significant or meaningful QUANTITY of food from which hana'a was derived is required.




            The absence of a berakha acharona upon eating less than a ke-zayit can be explained in one of two ways.  We might attribute it to the lack of a formal act of eating.  Alternatively, we might not require this formal act but still demand a significant quantity of food.  Less than a ke-zayit does not meet this mark.


            What would happen if less than a shiur of solid food were eaten along with less than a shiur of liquid so that their COMBINATION clearly surpasses the minimum shiur required.  Would a berakha acharona be necessary given the overall volume of "food" which was eaten?  The Magen Avraham (210:1) rules that the volume may be amassed using liquids and solids.  If the threshold of ke-zayit must be reached in order to secure a proper ma'aseh akhila, it would be very difficult to fashion such an act out of this combination of eating and drinking.  The action of eating and that of drinking are dissimilar and one cannot combine them into a single motion.  If, however, we are not concerned with the formal act of eating per se, but rather are interested in amassing a measure of food so that we have a significant amount, one might combine a quantity of food with drink so that together we have such a volume.


            Furthermore, if the only factor affected by the ke-zayit bulk is the significance of the "cheftza" (item) of food, we might consider alternate routes to achieving this status.  The Yerushalmi in Berakhot cites the very same episode of R. Yochanan reciting a berakha acharona upon a diminished olive.  The Yerushalmi, however, provides a different solution.  Since the olive was a complete "beryah" (whole organism or body, as opposed to sliced or cut food), the shiur of ke-zayit is not necessary.  The source for this halakha of berya is the mishna in Makkot which cites the following position of Chakhamim.  Though, in general, Chakhamim assert that an issur is transgressed only if a ke-zayit of tevel (grain prior to the separation of teruma) has been eaten, they admit that if an entire worm is eaten, even if it is smaller than a ke-zayit, malkut is administered.  Typically, this halakha is explained based upon the inherent significance which a berya possesses.  Said otherwise, the importance it lacks in quantity it compensates for in quality.  Though we might dismiss a few crumbs of bread as halakhically insignificant, we cannot similarly ignore a whole ant or a worm (see especially Rav Chayim Halevi al HaRambam Ma'akhalot Assurot 4:3).  Ostensibly, the Yerushalmi's mandate for berakha acharona upon a berya despite its deficient mass would cast the requirement of ke-zayit as one which grants significance to the food item.  A berya, provides this due to its nature, not its bulk, compensates with qualitative value.  If, however, we view ke-zayit as a prerequisite for a ma'aseh akhila, which in turn is what requires the berakha acharona, it would be harder to say that such act has taken place without a ke-zayit, even if an entire berya was consumed.  A ma'aseh akhila might require an ABSOLUTE quantity  of food to be ingested.


            A third manifestation of this question might be the issue of the time in which the food was eaten.  Halakha determines the normal acceptable duration for the process of consuming a specific amount of food.  For example, a ke-zayit matza must be eaten within a "kedei akhilat peras" (lit., the time required to eat half a loaf, according to many positions nine minutes), else the person hasn't eaten; he has merely nibbled.  A halakhic act of eating requires a minimum amount of food to be ingested within a reasonable period of time.  What if a meaningful amount of food was indeed eaten but too slow to meet this standard?  For example, one who sips a large cup of coffee for half an hour might not have to recite a berakha acharona.  This issue is addressed by the Magen Avraham in the aforementioned location.  Again, this would, in theory, be dependent upon the reason for the ke-zayit requirement.  If a ke-zayit is necessary to ensure that significant amount of food was enjoyed, little attention should be paid to the manner and pace at which that food was eaten.  If, however, the ke-zayit shiur is the cornerstone of a ma'aseh akhila we might additionally require that this akhila be performed at a reasonable pace.




            Understanding the ke-zayit shiur as that which confers upon food its significance might allow liquids and solids to be combined to reach the shiur and would similarly allow another factor (such as organic completeness) to provide qualitative significance in place of quantitative.  We would not, however, demand that the food be eaten within a specific time frame.


            Tosafot in Berakhot (38b) raise an intriguing possibility:  Though a "case-specific" berakha acharona ("me-ein shalosh") requires a ke-zayit, what about reciting a generic "boreh nefashot" upon any food less than a ke-zayit?  If the ke-zayit is necessary to establish a ma'aseh akhila, and such an act is crucial to the recitation of a berakha acharona, one might wonder why ANY berakha acharona at all, including boreh nefashot, should be called for in such a situation.  If the lack of this action is so constraining that the prescribed berakha acharona is not recited, it is difficult to understand the proposed substitution of boreh nefashot as a solution.  If, however, a ke-zayit defines the minimum of food which justifies a berakha acharona UPON THAT PARTICULAR FOOD, we might well conclude that boreh nefashot be recited upon less than a ke-zayit.  Boreh nefashot does not address foodstuffs in the same direct manner that me-ein shalosh does.  It instead offers a general praise to Hashem for creating a diversity of beings and sustaining each one.  As it does not directly mention FOOD but general sustenance (e.g. air, materi, etc.) we might recite this berakha any time we have not eaten a significant amount of food but have still been nourished and sustained.


            Finally, we might question the decided absence of the ke-zayit requirement when it comes to berakha rishona.  If Rashi is correct and the shiur of ke-zayit for berakha acharona stems from the need for a ma'aseh akhila, which itself derives from the word "ve-akhalta" employed by the pasuk in reference to berakha ACHARONA, we may reject this shiur entirely in the case of berakha rishona.  Textually, the verb "akhalta" is not employed regarding berakha rishona (which, according to most opinions, isn't de'oraita but derabanan) and we have neither indication nor inclination to insist that a berakha rishona be governed by the execution of a formal act of eating.  In fact, many berakhot are recited prior to diverse acts of deriving pleasure (smelling aromatic substances, seeing fire) even though no act of eating was performed.  Accordingly, we can understand the lack of a required shiur for berakha rishona.  Alternatively, if less than a ke-zayit is inherently devalued and does not mandate a berakha akharona - one might question why it should compel a berakha rishona.  In fact, the Kolbo does quote a She'iltot which equates berakha rishona and berakha acharona in this very way, opining that neither should be recited if less than a ke-zayit was eaten.  This, of course, is not the accepted halakha.  If, however, one maintains the position that less than a ke-zayit is not halakhically valuable food, we might still distinguish between berakha rishona and berakha acharona along merely technical lines.  Theoretically, neither should be recited in the absence of a ke-zayit, but due to other concerns berakha rishona is nonetheless recited upon any amount.  For example, the Kesef Mishneh in Berakhot 3:12 offers the following technical distinction: In the case of berakha rishona, though he plans to eat less than a shiur, he might change his mind and eat more. Hence, to protect against this contingency, he recites a berakha rishona on less than a ke-zayit.  In theory, one should only recite a berakha rishona on  more than a ke-zayit; since this cannot be realistically determined beforehand, a berakha is always recited.




1)  Oftentimes, a halakhic requirement is necessary to properly define an action (such as a halakhically valid act of eating).  In other instances it characterizes an item (such as a halakhically significant quantity of food).


2)  The question of the definition of ke-zayit applies almost any time this shiur is needed.  For example, why must one eat a ke-zayit of matza so that he has performed the act of eating, or to insure that he has eaten a significant quantity of food?




1)  See the Rashba in Berakhot who cites the Ra'avad that although a berakha rishona is recited over less than a ke-zayit, the berakha of hamotzi may only be recited if one plans to eat a ke-zayit.  How might this exception to the rule of berakha rishona be explained?

2)  What about drinking less than a ke-zayit of something which is normally consumed in small quantities - for example, a very sharp dip which is tasted or a small amount of whiskey which is drunk.  See the Taz 210:1.



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