QUESTION: The Gemara earlier says that one is not permitted to "roll ears of wheat" in order to remove the kernels on Shabbos. However, the Gemara here says that one is permitted to "peel barley" by the cupful in order to remove the seeds on Shabbos. Why is this permitted more than rolling ears of wheat?
Moreover, the fact that the Gemara permits one to peel barley on Shabbos implies that the barley has not yet been brought to the silo, because barley is brought to the silo only after the husks have been peeled off. If, however, the barley has not yet been brought to the silo, then clearly the barley has not yet undergone the procedure of Miru'ach and has not become obligated in Ma'aseros. When one peels the seeds of barley on Shabbos into his hand, they should become obligated in Ma'aseros at that moment, since the act of peeling is the "Gemar Melachah," the final processing of the barley. Ma'aseros, though, cannot be separated on Shabbos. Why is one permitted to peel the barley on Shabbos if he will not be able to eat it since he cannot separate Ma'aseros from it on Shabbos? The barley should be Muktzah.
Finally, why does the Gemara refer to "peeling" barley and "rolling" wheat? What is the difference between peeling and rolling? Both actions remove the outer shell of the kernel.
(a) TOSFOS (DH v'Im) and TOSFOS RABEINU PERETZ explain that there are two different shells around the kernel of wheat. There is a thin shell which lies directly on top of the kernel, and there is a thick shell which houses the kernel and its peel. When the Gemara (12b) says that one may not roll ears of wheat, it refers to wheat within both coverings, the outer husk and the inner peel. Rolling the wheat in order to remove the outer husk is prohibited because of Dishah (mid'Rabanan).
When the outer covering was separated from the seed before Shabbos, the seed may have been in the silo (after Miru'ach) and thus Ma'aser may have been separated from the barley before Shabbos. The barley which one wants to peel on Shabbos is not Muktzah since Ma'aser was already separated from it. The seed has only the thin, inner covering left over the kernel. One is permitted to peel off that inner covering on Shabbos. (The removal of the inner peel is not considered Dishah, just as the removal of the peel of a fruit is not considered Dishah. Dishah involves the removal of the container of the produce (such as the outer husk). The peel does not contain the fruit but merely protects it.)
When the Mishnah says that one who peels ("Mekalef") barley and places it into his hand is obligated to separate Ma'aseros, it refers to barley that was not yet brought to the silo, even though its outer covering was already peeled off, and thus it becomes obligated in Ma'aseros only now when its inner peel is removed.
This also explains why the Mishnah uses the term "peeling" ("Mekalef"). It refers to the removal of the inner peel and not to the outer husk.
(b) RASHI (DH v'Ochel), in contrast to Tosfos' explanation, explains that "Mekalef" refers to removing barley from its outer covering. Why, then, is "Mekalef" not considered Dishah, while "Molel" is? Perhaps Rashi understands that removing the covering by peeling, rather than by crushing the entire item, is not considered Dishah. That is why "Mekalef" is not Dishah, and why the act is called "Mekalef" in contrast to "Molel."
Why does the barley not become obligated in Ma'aseros at the moment one peels it? TOSFOS RABEINU PERETZ suggests that the Gemara refers to when one separated (on Shabbos) Ma'aser on behalf of this barley from other barley which had already undergone the process of Miru'ach (see Kidushin 62a).
OPINIONS: The Gemara concludes that "Melilah," or rolling grains in one's fingers in order to remove the chaff, is prohibited on Shabbos. (According to RASHI and TOSFOS (DH Keitzad Molel), it is prohibited on Shabbos even when done with a Shinuy, and it is permitted on Yom Tov only with a Shinuy. According to the RIF and ROSH, it is permitted on Shabbos with a Shinuy, and it is permitted on Yom Tov even without a Shinuy.)
Is one permitted to remove peas from a pod on Shabbos? Does the Halachah of Melilah apply to all types of foods that are contained within a natural shell?
The MAGEN AVRAHAM (OC 319:8) and ELYAH RABAH (OC 319) write that removing peas from their pod is not considered Dishah because one could eat the pea while it is inside the shell. Since the shell is edible, its removal is not similar to Dishah which involves the removal of an inedible part from an edible part.
What is the Halachah with regard to opening walnuts, peanuts, and sunflower seeds on Shabbos or Yom Tov? The BA'AL HA'TANYA (in his Sidur) and the ARUCH HA'SHULCHAN (OC 319:25) indeed prohibit opening nuts on Shabbos because their shells are not edible. However, the Mishnah in Shabbos (122b, 143a) clearly seems to permit cracking nuts open on Shabbos. Why is it permitted if the shell is inedible?
(a) The TAZ (OC 319:4) suggests that if the seeds are loose inside the shell (for example, when one shakes the nut he hears the fruit inside bouncing around), then one is permitted to open them. The Taz implies that the act is considered Dishah only when one removes a shell which is attached to the fruit.
The IGLEI TAL (Meleches Dash 15:3), however, questions this ruling from the words of RASHI in Shabbos (95b) who says that milking a goat is considered "Mefarek," a form of Dishah, even though the milk is not connected to the udders. Indeed, the MAHARIL (cited by the Elyah Rabah loc. cit.) and the PRI MEGADIM (introduction to OC 320) write the opposite: if the fruit is attached to the shell, then removing it is not considered Dishah; only when the fruit is not naturally attached to its containing shell is the removal of the shell considered Dishah.
(b) The IGLEI TAL (Meleches Dash 3:2) writes, based on the SEFER HA'TERUMAH, that any item which people normally open at the time they eat it is not considered Dishah. Only when an item is separated from its shell far in advance is the act considered Dishah. The TZITZ ELIEZER (10:24) writes that the common use of the fruit determines whether or not the removal of its shell is considered Dishah or not: if a fruit is opened just before it is eaten most of the time, then even though there are those who open it in advance (such as food production factories), the removal of its shell or peel is not considered Dishah. RAV MOSHE FEINSTEIN zt'l (IGROS MOSHE OC 1:125) gives a similar explanation.
(c) The PRI MEGADIM (in ROSH YOSEF here) writes that he does not understand the basis for the doubt in the first place. During the normal course of eating a meal, one certainly is permitted to open the shell of a nut because that is the normal manner of eating the item ("Derech Achilah"), and the prohibitions of Borer and Dishah do not prevent a person from eating in the normal manner of "Derech Achilah."
HALACHAH: The MISHNAH BERURAH (OC 319:24) permits cracking open nuts for immediate consumption (he does not give the reasons for why he permits it).