Whenever the commissioner has reason to believe that any provision of law relating to the manufacturing, processing, distribution, handling and sale of food, or rule issued by the commissioner thereunder, has been violated, the commissioner may suspend or revoke a license or permit granted under section 28A.04, or may limit the permission of the license or permit to only those aspects of the licensee's or permittee's business which are in conformity with the law and rules. Any person may be restrained by injunction from engaging in any business operation or category thereof for which that person is not validly licensed or for which a permit has not been issued. This suspension or revocation shall be made only after notice to the licensee or permittee and an opportunity to be heard with reference to the grounds for suspension or revocation, and this action by the commissioner shall in no way exempt such licensee or permittee from the penalties otherwise imposed in this chapter. The commissioner shall serve upon the licensee or permittee by registered letter containing a copy thereof, an order to show cause why the license or permit should not be permanently revoked, stating the grounds thereof, and the time and place of hearing, which time shall not be less than ten days after the date of mailing of the order. At the appointed time and place, and at such times as the matter may be adjourned to, the commissioner, or an appointed hearing officer, shall hear all proper evidence relating to the cause of the proposed revocation and, within a reasonable time thereafter, shall make and file a decision of the matter and forthwith mail to the licensee or permittee a copy thereof.