For producers to be able to set a correct shelf life on their bread products, it is essential to have a reliable method to validate the performance of their antimicrobial solutions. Different mold species and strains react differently to antimicrobials, such as Calcium-propionate, vinegar or fermented ingredients. To highlight the importance of understanding each plant’s unique microflora, we will show the impact of strain selection and variability on the outcome of mold challenge studies.