This study shows that it is possible to obtain pure alpha-glycine or a mixture of glycine polymorphs (alpha and gamma) in aqueous solution, depending on the mode of preparation, either continuous or semi-continuous. The differences between the two samples of glycine in solid state and in aqueous solution have been studied, using the following techniques: X-ray analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermal microscopy, calorimetric analysis, thermally stimulated current (TSC) analysis and electrochemical impedance analysis. These analyses show that the presence of gamma-glycine significantly modifies the physico-chemical properties of these two samples. (C) 2010 Elsevier B.V. All rights reserved.