Cheese ripening is a time-consuming and expensive process, in which the characteristic cheese flavour is formed by lactic acid bacteria (LAB). In his research project, Oscar van Mastrigt aimed to produce cheese aroma compounds outside the cheese matrix by using slow-growing LAB in retentostat cultures. These cultures mimic conditions in cheese, in which nutrients are limited leading to slow growth. To survive the extreme nutrient limitation, the bacteria decreased their maintenance energy requirement mainly by reducing protein synthesis. Aroma formation by the slow-growing LAB resembled aroma formation during cheese ripening, while this is not the case for fast-growing LAB. This observation demonstrates the potential of the newly developed strategy to produce cheese aroma compounds. By using a dairy-based substrate and/or by co-cultivation of different LAB, aroma formation can be further tailored for specific food applications.