When the director determines that such action will promote honesty and fair dealing in the interest of consumers, the director shall promulgate regulations establishing for any food or class of food a reasonable definition and standard of identity, or reasonable standard of quality or fill of container or any combination thereof. In prescribing a definition and standard of identity for any food or class of food in which optional ingredients are permitted, the director may designate the optional ingredients which shall be named on the label. The definitions and standards so promulgated shall conform so far as practicable to the definitions and standards promulgated under authority of the federal act. The director shall not establish standards for any food or class of food regulated for any other state agency.