Parashas Bo · Shemos 12:16 · TT note 4
Torah Temimah on Shemos 12:16, note 4 (on אַךְ אֲשֶׁר יֵאָכֵל juxtaposed with matzos) points to Yerushalmi Beitzah.
Sefaria — Exodus 12:16
Sefaria — Torah Temimah on Exodus 12:16
Sefaria — Yerushalmi Beitzah 1:10
English: From here [we learn] that one may not sort, grind, or sift on Yom Tov.
Boundary of ochel nefesh: preliminary labors remain forbidden.
Sorting, grinding, and sifting are not permitted under the food exception; only later stages of food prep that cannot be done earlier are allowed.