סימן פ סעיף טו

אֹכֶל הַמְעֹרָב עִם פְּסֹלֶת, מֻתָּר לִבְרוֹר אֶת הָאֹכֶל מִתּוֹךְ הַפְּסֹלֶת, אֲבָל לֹא אֶת הַפְּסֹלֶת מִתּוֹךְ הָאֹכֶל. וְגַם אֶת הָאֹכֶל, אָסוּר לִבְרוֹר עַל יְדֵי כְּלִי, אֶלָּא דַּוְקָא בַּיָּד. וְדַוְקָא מַה שֶּׁהוּא צָרִיךְ לֶאֱכוֹל מִיָּד. וַאֲפִלּוּ בְּמַאֲכָלִים שֶׁרוֹצִים לִבְרוֹר מַה שֶּׁיֹּאכְלוּ עַתָּה מִמַּה שֶּׁיַּשְׁאִירוּ, צְרִיכִין לִזָּהֵר לִבְרוֹר מַה שֶּׁרוֹצִים לֶאֱכוֹל עַתָּה, וְלֹא לִבְרוֹר מַה שֶּׁרוֹצִים לְהַנִּיחַ. כִּי מַה שֶרוֹצִים לֶאֱכוֹל עַתָּה, חָשׁוּב אִכֶל. וּמַה שֶׁרוֹצִים לְהַנִּיחַ, חָשׁוּב פְּסֹלֶת. אֲפִלּוּ לִקְלוֹף שׁוּם אוֹ בְּצָלִים וּלְהַנִּיחָם, אָסוּר מִשּׁוּם בּוֹרֵר, וְאֵינוֹ מֻתָּר לִקְלוֹף אֶלָּא מַה שֶּׁצְּרִיכִין לֶאֱכוֹל מִיָּד (שי"ט שכ"א). וְהַקְּלִפָּה הָעֶלְיוֹנָה שֶׁעַל הַשּׁוּם הַמְסַבֶּבֶת כָּל הַחֲלָקִים, יֵשׁ לֶאֱסוֹר לַהֲסִירָהּ אֲפִלּוּ לְצֹרֶךְ אֲכִילָה מִיָּד, מִשּׁוּם דַּהֲוֵי מְפָרֵק, תּוֹלָדָה דְּדִישָׁה (פְּרִי מְגָדִים סִימָן שי"ט. אֵשֶׁל אַבְרָהָם סָעִיף קָטָן ח'. הִנִּיחַ בְּצָרִיךְ עִיוּן, עַיֵן שָׁם)

When food is mixed with pesoles,⁶⁴Pesoles, which means waste, refers to matter that is presently unwanted. you may separate [select] the food from the pesoles,⁶⁵Even if the majority is pesoles. (Peri Megadim 319: 3) However, most poskim disagree with this ruling. but not the pesoles from the food. And even separating food from pesoles is forbidden when using a utensil.⁶⁶Using a utensil designed for selection (e.g. a strainer, etc.) is prohibited, even for separating food from pesoles for immediate use. Even if you intend to eat both species immediately, you may not use such utensils according to Biur Halachah 319: 1.
Using utensils not designed primarily for selection but which make it easier, is a deoraisa violation except when separating food from pesoles to eat immediately. In this case it would be a Rabbinic prohibition lest it lead to using a strainer or sieve [see Shulchan Aruch Harav]. The use of cutlery to facilitate the process of selection is a shevus (Rabbinic prohibition) and should not be used to separate the food from the pesoles, even for immediate use [see Igros Moshe Resp. 124]. This is only if the utensil essentially enhances the selection process; but if it is used because of cleanliness, it may be used to separate food from pesoles when eaten immediately. It is permitted only by hand,⁶⁷Or fork, etc. If they do not, in essence, facilitate the selection process. (see Igros Moshe, Resp. 124 and footnote 66)
You may hand-select the food from the pesoles to eat immediately because this is considered the normal way of eating and is not considered a melachah of boreir (selecting). The classic case of boreir is when one selects or separates something for later usage, and does so with a helpful utensil, or removes pesoles from food. (Magein Avraham 320: 7, Mishnah Berurah 320: 10 etc.) and only for the purpose of eating it immediately.⁶⁸Immediately, in this case, has various definitions: some say it means for the following meal of that day, even if it is many hours later [Beis Yosef according to the Bach]. Others say no more than one hour before the meal [Meiri Maseches Beitzah 14b], Shulchan Aruch Horav, see Eglei Tal. Still others maintain it has to be exactly before the meal. See Eglei Tal. Others hold that an hour in this instance is not absolute, but only represents the normal way of preparing the meal, which can be much less than an hour [Igros Moshe]. Extreme care should be taken to avoid this unclear situation, since it is a safeik (doubt) of a deoraisa violation.
However, if it is impossible to eat without separating the pesoles from the food (bony fish for the very young or old), they may remove the pesoles from the food and eat it immediately [from hand to mouth. Initially, however, you should try to remove the bones while leaving some of the flesh on it.] This is the only way you eat it without violating the melachah of boreir (selection) [see Mishnah Berurah 321: 84—Peri Megadim]. This is probably permitted only if you are feeding yourself, but if you are feeding someone else, you may not be allowed to remove the pesoles from the food and put it into his mouth. Even foods which you select to eat now, from food which will be left for later use, care must be taken to select only what is to be eaten now, and not to select that which will be left over,⁶⁹According to Mishnah Berurah, Rambam’s view is that doing so constitutes a definite violation of Boreir. because the part to be eaten now is considered food and the part to be left over is considered pesoles. Even peeling garlic or onions and putting them away is prohibited,⁷⁰Rema (321: 19) —Semag, etc. because of boreir (selecting). You are permitted to peel only what you need for eating⁷¹Even though you are separating the pesoles from the food, which is prohibited even if done for an immediate meal, since there is no other way to remove it from its peel, this is the way it is eaten and it is not considered boreir. (Biur Halachah 321: 19) now.⁷²Magein Avraham considers apples in the same category as garlic or onions and so does the Mishnah Berurah 321: 84. The outermost peel of the garlic, that surrounds the whole cluster must not be removed even to eat the garlic now,⁷³Mefareik, even for immediate use is prohibited. (Magein Avraham 320: 7) because it is considered mefareik,⁷⁴The melachah of dosh (threshing) is done with a utensil. When extraction of the pesoles is done by hand, it is mefareik, a toldah. (Shulchan Aruch Harav 319: 9) a toldah [offshoot melachah] of dosh (threshing).

תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)