One may remove peels from fruit in order to eat them. Even though removing the peel is similar to removing psolet from okhel, it is not forbidden because this is the normal way to eat a fruit that has a peel. Therefore, one may peel garlic, onions, nuts, eggs, grapefruits, bananas, oranges, etc. for immediate consumption. However, one may not peel them to eat later on, because that is derekh melakha (Rema 321:19). For immediate consumption, one may remove a peel with a knife because it is a utensil designed to help one’s hand through derekh akhila and not derekh melakha (see Igrot Moshe OĤ 1:124).
When one who is eating a plum reaches the pit, he may throw it out and continue eating. One who is eating apricots or dates may open them (and check them for bugs), throw out the pit, and eat them, because this is the normal way of eating these fruits (MB 321:84).
One who is cutting up a melon for immediate use may throw out all the seeds, because removing them is comparable to removing the peel of a fruit. Similarly, one may remove the peel of a melon or watermelon immediately before eating it. One may also remove the stem of a fruit before eating it (SSK 3:18 and 3:37-39; compare to section 10 below, which explains that one may remove watermelon seeds before eating watermelon).
The poskim disagree whether removing the edible peel of fruits or vegetables, like those of apples, pears, cucumbers, and carrots, presents a problem of Borer. Some say that since the peel can be eaten, there is no issue of Borer, but rather it is like cutting a fruit in two. Thus, one may peel them even to eat later on, and may even use a peeler to do so. Others maintain that since one does not want the peel, it is considered psolet for him, and the rules of Borer apply to it. Accordingly, a peeler is considered an implement designed for separating, and therefore it absolutely may not be used. However, one who wishes to be lenient has support for doing so. One may still peel these fruits with a knife for immediate consumption.
. Beit Yosef and Rema 321:19 quote Smag, Rabbeinu Yeruĥam, Smak, Terumat Ha-deshen, and Hagahot Maimoniyot, all of whom maintain that one may not peel garlic and onions for later because of Borer (though one may do so for immediate use, as that is derekh akhila). However, it seems from some Rishonim (Rabbeinu Ĥananel, Arukh, and Me’iri) that Borer does not apply to a case where the psolet and okhel are attached to each other. There is a dispute about what this means: Tal Orot explains that Borer does not apply at all to cases where the peel is fully attached to a fruit or vegetable, as with an orange. In contrast, in cases such as onions or garlic, where the peel is more loosely attached, Borer does apply (cited in Yalkut Yosef 319:57-58). Others explain that these Rishonim mean that when psolet and okhel are found side by side, whether joined completely or more loosely attached (like onion and garlic), Borer does not apply, because Borer is relevant only when psolet and okhel are mixed together (summarized in Menuĥat Ahava 2:7:39-41). In practice, since this is a case of uncertainty about Torah law, the vast majority of poskim rule stringently. This is the explicit ruling of Beit Yosef and Rema 321:19, and is the position of MA and MB 321:83 as well. Therefore, one may peel garlic and onions for immediate use only. However, where there are additional uncertainties, the lenient view is taken into consideration.. There are three opinions on this matter:
1) MA 321:30 and MB 321:84 forbid peeling apples for later. This implies that the rules of Borer pertain to the removal of a peel. This is also the opinion of Igrot Moshe OĤ 4:74, Borer 8. Similarly, Responsa Maĥazeh Eliyahu §51 forbids using a peeler, as does Ayil Meshulash, p. 104.
2) SSK 3:34, nn. 88 and 90, presents as the first and primary opinion that if most people regularly eat the peel of a given fruit or vegetable, it may be peeled even with a peeler, and even for later consumption (this also seems to be the opinion of Pri Megadim as cited in SHT ad loc. 97).
3) Some maintain that even if a peel is only eaten in distressing circumstances and only together with its fruit, Borer does not apply, since the peel is part of the fruit. We may combine this view with the opinion of Rabbeinu Ĥananel and others who maintain that Borer does not apply to removing peels (as explained in the previous note) as well as the opinion of those who maintain that one may perform Borer even with a utensil if it is for immediate use (as explained in n. 1 above). This is also the position of Menuĥat Ahava 2:7:13. Yalkut Yosef 319:58, 61 states that those who are lenient have an opinion to rely on. (We might suggest that even those who prohibit this do so rabbinically, which might be inferred from the laws of separating leaves that are edible but not usually eaten, as explained in MB 319:7.) She’arim Metzuyanim Ba-halakha §80, Kuntres Aĥaron 24 permits using a peeler on the grounds that it is comparable to a knife, rather than an implement specifically used for separating. It would seem that le-khatĥila one may rely on the second opinion, and there are grounds to be lenient in accordance with the third opinion as well.