From: Rabbi Akiva Eiger
To: Rabbi Shlomo
Rabbi Akiva Eiger analyzes whether grinding wheat containing worms that may have separated and returned constitutes forbidden bitul issur l'chatchila. He rules that in cases of significant financial loss, grinding is permitted provided the mill has an aparkeses sieve and buyers sift the flour in daylight and discard visible worms.
Source: Shu"t Rabbi Akiva Eiger §77