When optimizing the process of grape juice manufacture not just to obtain an excellent quality, but also to develop a data base is essential to know the evolution of physical properties, such as density or boiling point elevation. These properties are affected by pressure, temperature and solid content. The aim of this work was to establish a mathematical relation between these variables. In order to assess and select a suitable mathematical model the known data were fitted in different equations. Tests results have shown that at constant dry matter content the pressure and the boiling point are related by a “shifted power” equation while between temperature and density variation a logarithmic model seems to be the most appropriate.