An investigation into lactose crystallization under high temperature conditions during spray drying

Lactose crystallization was studied at high temperature conditions in a Buchi B-290 mini spray dryer. The inlet gas temperature was 200 °C, and an insulating material was used to reduce the heat loss from the drying chamber (outlet temperature 157 °C), thus increasing the gas and particle temperatures. At these conditions, lactose crystallinity was found to increase significantly compared with a case where it was spray dried at 170 °C in a non-insulated drying chamber (outlet temperature 90 °C), but the process yield was lower for the former case (0.16% yield) than for the low temperature conditions (47% yield). There is some evidence that high-temperature spray drying of lactose is more likely to give more β-lactose anomer. Different analytical techniques (Fourier Transform Infrared Spectroscopy, modulated differential scanning calorimetry, moisture sorption test, Raman spectroscopy) were used to investigate the degree of crystallization and possible lactose anomer formation during this spray drying at high inlet gas temperatures.