(b) In the event of findings by the department that there is an existing or imminent shortage of any ingredient required by section 328-72 or 328-73, and that because of such shortage the sale and distribution of flour or white bread or rolls may be impeded by the enforcement of sections 328-71 to 328-76, the department shall issue an order, to be effective immediately upon issuance, permitting the omission of the ingredient from flour or white bread or rolls; and if it finds it necessary or appropriate, excepting such foods from the labeling requirements until the further order of the department. Any such findings may be made without hearing, on the basis of an order or of factual information supplied by the appropriate federal agency or officer. In the absence of any such order of the appropriate federal agency or factual information supplied by it, the department on its own motion may, and upon receiving the sworn statements of ten or more persons subject to sections 328-71 to 328-76 that they believe such a shortage exists or is imminent shall, within twenty days thereafter hold a public hearing with respect thereto at which any interested person may present evidence; and shall make findings based upon the evidence presented. The department shall publish notice of any such hearing at least ten days prior thereto. Whenever the department has reason to believe that the shortage no longer exists, it shall hold a public hearing, after at least ten days' notice shall have been given, at which any interested person may present evidence, and it shall make findings based upon the evidence so presented. If its findings are that the shortage no longer exists, it shall issue an order to become effective not less than thirty days after publication thereof, revoking the previous order; provided that undisposed floor stocks of flour on hand at the effective date of the revocation order, or flour manufactured prior to the effective date, for sale in this State may thereafter be lawfully sold or disposed of.