Yes / It is important for the formulators of biopharmaceuticals to predict the folding–unfolding transition of proteins. This enables them to process proteins under predetermined conditions, without denaturation. Depending on the apparent denaturation temperature (Tm) of lysozyme, we have derived an equation describing its folding–unfolding transition diagram. According to the water content and temperature, this diagram was divided into three different areas, namely, the area of the water-folded lysozyme phase, the area of the water-folded lysozyme phase and the bulk water phase, and the area of the denatured lysozyme phase. The water content controlled the appearance and intensity of the Raman band at ∼1787 cm–1 when lysozyme powders were thermally denatured at temperatures higher than Tm. / MAM gratefully acknowledges CARA (Stephen Wordsworth and Ryan Mundy) and University of Bradford for providing an academic fellowship.