For what it's worth THE USP is a pharma lobbying group that makes recommendations on standards to the US government. Also in order to be "Food Grade" something most FIRST be USP-NF certified. The NF part is the Government and NOT always printed on the label. ONLY those things with the NF are OFFICIALLY certified by the FDA.
part of the wiki.
The United States Pharmacopeia (USP) publishes an official compendium in a combined volume with the National Formulary as the USP-NF. The United States Pharmacopoeial Convention (usually also called the USP) is the nonprofit organization that owns the trademark and copyright to the USP-NF and publishes it every year. If a drug ingredient or drug product has an applicable USP quality standard (in the form of a USP-NF monograph), it must conform in order to use the designation "USP" or "NF." Drugs subject to USP standards include both human drugs (prescription, over-the-counter, or otherwise), as well as animal drugs. USP-NF standards also have a role in U.S. federal law; a drug or drug ingredient with a name recognized in USP-NF is deemed adulterated if it does not satisfy compendial standards for strength, quality or purity. USP also sets standards for dietary supplements, and food ingredients (as part of the Food Chemicals Codex). USP has no role in enforcing its standards; enforcement is the responsibility of FDA and other government authorities in the U.S. and elsewhere.