Amidst the current challenges of the food industry optimizing planning processes within production becomes imperative. Due to a shortage of skilled workers, heterogeneous qualifications, and interdependencies between departments and workers, efficient workforce assignment is critical. This work studies a real-world worker assignment problem of a German organic food company to aid in this pivotal endeavor. The main particularity is the consideration of a heterogeneous workforce regarding workers' qualifications and skill levels. Additionally, this work includes production-based time intervals as well as shift plans. An integer linear programm (ILP) is introduced to assign the workforce optimally by minimizing inefficient assignments and the use of temporary workers. The ILP is used to present a worker schedule to the personnel planners as real-world decision support. Additionally, the solutions point out the company's worker assignment potential, revealing staff utilization inefficiencies, qualification shortages, and imbalances.