Section 107. The commissioner of food and agriculture and his duly authorized assistants shall have authority to enforce section ninety-nine B, sections one hundred and one to one hundred and five, inclusive, and one hundred and nine, and to prosecute all violations thereof. Before any prosecution is begun by the commissioner of agriculture or any of his duly authorized assistants the parties concerned shall be given an opportunity to be heard before the said commissioner or a person designated by him for such purpose. The parties concerned shall be given reasonable notice of hearing, specifying the day, hour and place thereof and accompanied by a description of the alleged violation. Such hearings shall be governed by rules and regulations prescribed by said commissioner.