The effect of temperature on the crystallinity of lactose powders produced by spray drying

The effect of varying the inlet air temperature over the range from 134 °C to 210 °C on the degree of crystallinity for spray-dried lactose powders (from ∼55% crystalline to ∼76% crystalline) has been studied experimentally in a Buchi-290 laboratory-scale dryer, since the temperature is likely to be important according to the Williams–Landel–Ferry theory for solid-phase crystallization. The increased crystallinity at higher-temperatures has been measured by water-induced crystallisation, X-ray diffraction, modulated differential scanning calorimetry and pore size and volume analysis, with all techniques showing consistent results. The results indicate that the degree of crystallinity in spray-dried products can be controlled by adjusting the operating conditions.