The following is a FAQ from the Missouri Department of Labor and Industrial Relations (DOLIR) website:

Are breaks or lunch periods required?

There are no state laws regarding breaks or lunch periods. These issues might be addressed by company policy, or could be covered by union contract. This applies to hourly as well as salaried employees. Make sure you are in compliance with board policy. If your policy does not allow lunches or breaks, it may be a discussion topic for your staff welfare committee or bargaining representative.