Section 30. The said chief of the bureau of milk marketing and his agents shall enforce sections twenty-five through thirty-one, inclusive, and the rules and regulations made thereunder, and may prosecute or cause to be prosecuted any person violating any provision thereof. The said chief of the bureau of milk marketing or his agents shall enter upon any premises, including bulk tank trucks, where samples of milk or cream are taken, stored or tested for the purpose of inspection or as a basis for payment in buying or selling in order to determine whether said sections, rules and regulations are being properly observed. Said sections, rules and regulations shall not be construed to apply to any person determining milk-fat or other component content of milk or cream solely in connection with an educational and informational service to dairy farmers, provided that the director or his agent shall, with respect to any such person, be responsible for carrying out the provisions of sections twenty-five and twenty-six and for issuing certificates of competency as provided in sections twenty-seven and twenty-seven A.