Upon the approval of an assessment or a change in assessment in accordance with this chapter, the commissioner shall notify forthwith, by certified mail, all persons engaged either in the business of purchasing milk directly from producers or marketing milk in this state, either individually or on behalf of producers, that on and after the date specified in such letter, the specified assessment shall be deducted from the producer's payment for the sale or marketing of milk. The assessment so deducted shall, on or before the twenty-fifth day of the month following the end of the month in which milk is sold or marketed, be remitted to the Tennessee dairy promotion committee established in this chapter. These funds, including donations from individuals, concerns, corporations and grants from state or governmental agencies, shall be used for the purpose of promoting and stimulating by advertising, research, nutrition education and other methods, the increased consumption, use and sale, of milk. The books and records relating to the payment of the assessment of all persons who purchase or market milk shall at all times during regular business hours be open for inspection by the commissioner or the commissioner's duly authorized agents.