Particle size distribution is a fundamental powder property that plays a crucial role in determining the functional properties of powders. It significantly influences critical dry powder characteristics such as bulk density, flowability and appearance. In many cases, to improve the handling and reconstitution characteristics, larger agglomerates and primary particles are often preferred. At Fonterra, we have developed innovative test methods to assess insoluble materials in reconstituted milk, whether they are present on the fluid surface, suspended within the liquid, or settled at the bottom of the container. This enables detailed observation of the dissolution process and identification of subtle differences among samples. Our findings indicate that optimizing particle size distribution significantly affects the dissolution process. In particular, we found that the dispersibility of powder was significantly enhanced when the finest particles were removed by sieving.

The spray drying process is pivotal in the production of dairy powders, designed to remove water while preserving product integrity. We assess the reversibility of water removal by comparing processability of liquid feeds and their respective powders. While the dehydration process itself is reversible, pre-drying modifications such as diafiltration induce significant changes in the mineral content. We utilized 31P solid state NMR as a novel approach to probe the dynamics of phosphorous containing casein components indicating diafiltered caseins to have increased mobility. These pre-drying interventions lead to modifications that persist through drying and impact the final product characteristics. Additionally, we investigated the crystallization behavior of lactose during the shelf life of dairy powders. Our findings indicate that lactose can migrate to the surface, forming crystalline structures that adversely affect the dissolution rate of the powder. We show that incomplete dissolution of powder ingredients result in poor product characteristics, i.e. water retention and brittleness, of acidified gels while the slower process of mineral equilibration between serum and micellar state have limited effect on gel characteristics. This research underscores the importance of understanding pre-drying modifications, reconstitution state and modifications during storage to optimize the quality and functionality of spray-dried dairy products utilized for recombined products.

The demand for functional foods that naturally contain or that are enriched with bioactive ingredients to achieve specific physiological benefits is constantly increasing. These bioactive ingredients in dairy products often pose challenges for food producers due to their sensitivity, which necessitates stabilisation to ensure bioavailability over the entire shelf life. Moreover, improved solubility and a time- or pH-dependent release is necessary to enhance the effect of the bioactive ingredients. Taste or odour masking is often required to ensure market acceptance. To overcome this technological challenges, encapsulation of the bioactive ingredients based on fluid bed technology can be applied. In this study, four process options and two spray pressures were applied to model particles, with the aim of identifying key parameters for time-dependent release control.
Model particles were produced as a representative basis. For this purpose, a spherical pellet was first coated with a NaCl as an active ingredient. A functional layer based on hydroxypropyl methylcellulose and neutral methacrylate co-polymer was then added to the model particles using four process options at a pilot-scale fluid bed machine: Wurster technique, top spray, bottom spray and rotor processing. Additionally, the influence of a spray pressure of 0.2 MPa and 0.25 MPa was also investigated. From the model particle, the particle size distribution, the hardness and the release profile of NaCl using a conductometer were measured.
The results showed that the spray pressure had no influence on the particle size distribution, but affects particle hardness and time release profile, which in turn depends mainly on the process options. This indicates that both functional layers and process options play a crucial role in achieving a specific time- or pH-dependent release of active ingredients. This study offers a basis to identify fluid bed process configurations for dairy producers, with the aim of fulfilling product quality requirements.

Customer expectations for functional high protein whey powders with consistent quality are greater than before. It is a challenge for dairy plants with older design of unit operations to keep up with them without large investment. In this particular example, we were looking into instantized Whey Protein Concentrate 80 (WPC80) and Isolate (WPC90) to meet functional requirement of rapid dissolution of high concentration protein powders at low temperature.

Several approaches related to spray drying were evaluated. Approaches such as changing lecithin applications, pre-heating of lecithin air disperser, and changing product nozzle configurations are discussed. Powder dissolution, particle size distribution, and other powder properties were measured and compared against control powders.

Increasing application of lecithin and changing product nozzle configurations were found to be successful as the approaches reduced the amount of small particles (fines) in the powder, improved particle size distribution, and improved wetting. This allows for consistent and improved dissolution performance of the powder. The approach of pre-heating lecithin air disperser however, did not show any appreciable dissolution performance.