Fast crystallization of lactose and milk powder in fluidized bed dryer/crystallizer

Abstract

The rationale of this study has been to produce stabilized dairy powders for longer-term ambient storage by partial crystallization of the sticky amorphous lactose component in vibrated fluidized beds. Various combinations of temperatures, humidities, and processing times were used to crystallize lactose and milk powder in a fluidized bed dryer/crystallizer to achieve different degrees of amorphicity of powder. Under these conditions, lactose crystallinity and the crystallinity of the lactose portion in milk powder were found to increase significantly compared with the amorphous powders that were produced by conventional spray dryers. Different analytical techniques were used to investigate the degree of amorphicity and the improvement in powder crystallinity, such as modulated differential scanning calorimetry, water-induced crystallization, and Raman spectroscopy. The resulting powders were not sticky and were produced by different experimental conditions of processing temperature as 50–70 °C and 40% relative humidity in 30–60 min processing time. This technique is able to crystallize amorphous lactose and lactose-containing powder after spray drying in a reasonable processing time.