The compositional and physicochemical properties of different whey permeate (WPP), demineralised whey (DWP) and skim milk powder (SMP) size fractions were investigated. Bulk composition of WPP and DWP was significantly (P < 0.05) influenced by powder particle size; smaller particles had higher protein and lower lactose contents. Microscopic observations showed that WPP and DWP contained both larger lactose crystals and smaller amorphous particles. Bulk composition of SMP did not vary with particle size. Surface composition of the smallest SMP fraction (<75 µm) showed significantly lower protein (-9%) and higher fat (+5%) coverage compared with non-fractionated powders. For all powders, smaller particles were more susceptible to sticking. Hygroscopicity of SMP was not affected by particle size; hygroscopicity of semi-crystalline powders was inversely related to particle size. This study provides insights into differences between size fractions of dairy powders, which can potentially impact the sticking/caking behaviour of fine particles during processing.

The α-relaxation temperatures (Tα), derived from the storage and loss moduli using dynamic mechanical analysis (DMA), were compared to methods for stickiness and glass transition determination for a selection of model whey protein concentrate (WPC) powders with varying protein contents. Glass transition temperatures (Tg) were determined using differential scanning calorimetry (DSC), and stickiness behavior was characterized using a fluidization technique. For the lower protein powders (WPC 20 and 35), the mechanical Tα determined from the storage modulus of the DMA (Tα onset) were in good agreement with the fluidization results, whereas for higher protein powders (WPC 50 and 65), the fluidization results compared better to the loss modulus results of the DMA (Tα peak). This study demonstrates that DMA has the potential to be a useful technique to complement stickiness characterization of dairy powders by providing an increased understanding of the mechanisms of stickiness.

Permeates are generated in the dairy industry as byproducts from the production of high‐protein products (e.g., whey or milk protein isolates and concentrates). Traditionally, permeate was disposed of as waste or used in animal feed, but with the recent move toward a “zero waste” economy, these streams are being recognized for their potential use as ingredients, or as raw materials for the production of value‐added products. Permeates can be added directly into foods such as baked goods, meats, and soups, for use as sucrose or sodium replacers, or can be used in the production of prebiotic drinks or sports beverages. In‐direct applications generally utilize the lactose present in permeate for the production of higher value lactose derivatives, such as lactic acid, or prebiotic carbohydrates such as lactulose. However, the impurities present, short shelf life, and difficulty handling these streams can present challenges for manufacturers and hinder the efficiency of downstream processes, especially compared to pure lactose solutions. In addition, the majority of these applications are still in the research stage and the economic feasibility of each application still needs to be investigated. This review will discuss the wide variety of nondairy, food‐based applications of milk and whey permeates, with particular focus on the advantages and disadvantages associated with each application and the suitability of different permeate types (i.e., milk, acid, or sweet whey).