REQUASUD developed reference materials based on the adsorption of bacterial spores on calcium carbonate pellets. The validation was performed by homogeneity tests, following of stability over time and interlaboratory comparisons.
Abdel Massih, M., Anceau, C., & Mahillon, J. (2011). Stable reference materials for food microbiology using B. cereus and Cl. perfringens spores. 16th Conference on Food Microbiology, Brussels. https://hdl.handle.net/2078.5/204818