It shall be the duty of the Commissioner to see that the provisions of this article are complied with, and he may in his discretion prosecute any person violating any of its provisions. But the provisions of this article shall not be construed to affect a person using any centrifugal or other machine or test in determining the composition or value of milk or cream when such determination is made for the information of that person only and not for purposes of inspection, or as a basis for payment in buying or selling.
Va. Code § 3.2-5231