Impact of Spray Drying Parameters on Lactose-Free Milk Powder Properties and Composition

Lactose-free milk powders are an interesting topic, as the industry still struggles with the enhanced stickiness of the material. To better understand this topic, an industrial scale spray-dryer was used to assess the influence of process parameters on the powder properties of lactose-free milk. A simple design of experiments was conducted varying the inlet temperature in combination with the atomization flow rate. The intention was to set different driving forces for drying in combination with the different surfaces are for mass transport. Yield is typically the process bottleneck, but from results, high inlet temperature combined with small droplet size resulted in a 50.73% yield. Powder's moisture contents were between 0.53% and 5%, and water activity between 0.21 and 0.43, being all values within a safety threshold for storage. From bulk and tap density results, all powders revealed to be cohesive with the Hausner ratio above 1.5. Color measurements revealed off white samples, with a tendency to become brown when higher inlet temperatures are used, possibly due to Maillard reactions. Powder particle size ranged from 5.6 to 13.5 mm and revealed extensive agglomeration, possibly due to some protein denaturation at the particle surface. Inlet temperature revealed to be the most influential parameter on all properties.