9 C.F.R. § 390.7
(a) If the request for information or for a waiver of search or duplication is denied, in whole or in part, the FOIA Coordinator or designee will explain in the letter of response the grounds for any denial of access and offer the requester an opportunity to file an administrative appeal, pursuant to 7 CFR 1.3(a)(4). The appeal should be filed in writing within 45 days of the date of denial (departmental regulations, 7 CFR 1.14) and addressed as follows:
Administrator, Food Safety and Inspection Service (FOIA Appeals), Department of Agriculture, Washington, DC 20250-3700