The quality requirements for butter shall be in accordance with the U.S. Standards for Grades of Butter for U.S. Grade AA, U.S. Grade A, or U.S. Grade B, respectively.

(a) In addition, the butter is subject to the following specifications when sampled and tested in accordance with §§58.336 and 58.337.

(b) Proteolytic count, not more than 100 per gram; yeast and mold count, not more than 20 per gram; coliform count, not more than 10 per gram.

(c) Optional except when required or requested: Copper content, not more than 0.3 ppm; iron content, not more than 1.0 ppm; enterococci, not more than 10 per gram.