21 C.F.R. § 1316.60
If any party in the hearing objects to the admission or rejection of any evidence or to other limitation of the scope of any examination or cross-examination, he shall state briefly the grounds for such objection without extended argument or debate thereon except as permitted by the presiding officer. A ruling of the presiding officer on any such objection shall be a part of the transcript together with such offer of proof as has been made if a proper foundation has been laid for its admission. An offer of proof made in connection with an objection taken to any ruling of the presiding officer rejecting or excluding proffered oral testimony shall consist of a statement of the substance of the evidence which the party contends would be adduced by such testimony; and, if the excluded evidence consists of evidence in documentary or written form a copy of such evidence shall be marked for identification and shall accompany the records as the offer of proof.
21 C.F.R. § 1316.60