Context As recommended by the FAO, the digestible indispensable amino acid score (DIAAS) is the best measure for assessing protein quality. Recently, a workflow for protein digestibility quantification and DIAAS calculation was developed based on the static INFOGEST in vitro digestion method. A first inter-laboratory study showed promising results and the standardisation process within the International Dairy Federation (IDF) and ISO was initiated to establish an international ISO/IDF standard method. Currently, a second inter-laboratory study, involving more than 30 laboratories around the world is undergoing. This involves determining and statistically evaluating the protein digestibility and DIAAS values of five dairy products and two plant sources.