The use of natural whey starter (NWS), also named "backslopping", is still widespread for several cheese-making processes. This practice plays a decisive role in the cheese typicity but can also lead to technological defects. A lack of knowledge exists concerning these problems. In this research, "Tomme" cheese variety is used as a model to study backslopping. A starter made of three characterized lactic acid bacteria (LAB) strains was used on day one. During the 10 following days, the whey was used from one day to the other as NWS. The milk used was pasteurized and re-seeded with identified strains of LAB to mimic the contribution of the raw milk flora. As expected, the pH evolution during molding changed from day to day. The analysis of the compositional data, and among them, moisture in non fat cheese and calcium on non fat dry matter, and the use of a statistical PLS approach allowed to prove that pH fluctuations were simply explained by the evolution of the composition of NWS. These results reinforced the accuracy of the model to study backslopping. (C) 2008 Elsevier Ltd. All rights reserved.