Determination of limiting factors in a novel superconcentration-granulation based dairy powder manufacturing process

An innovative approach based on superconcentration and granulation was investigated to manufacture dairy ingredients at lab-scale. A wet mass characterization technique, which measured agitator current consumption, was developed to study cohesiveness of super-concentrated products at various dry matter (DM) contents. For all ingredients, a composition-dependent cohesive phase was observed as DM increased, which was typified by a sharp rise and subsequent fall in power consumption. The effect of powder back-mixing on granulation was studied using three superconcentrate:powder (w/w) ratios (1:0.8, 1:1 and 1:1.2, respectively). Minimum powder addition rate for successful granulation was related to DM content at the end of the cohesive phase. Granulated powders had larger particle size, higher densities, lower porosities and enhanced flow properties compared to commercial spray-dried powders. The lab-scale model provided useful information on physical properties and limits during superconcentration and granulation, which increases the scientific knowledge relating to this novel powder production approach. Industrial relevance: Spray drying is the most widely utilized powder manufacturing technology in the dairy industry, especially for producing ingredients and nutritional products. It is, however, extremely energy intense and therefore spray drying of high-volume, low-value dairy streams such as permeate represents a poor use of resources for industry. An alternative spray dryer-free process has been developed for such streams, with significant savings. This process is based on superconcentration of streams to DM content in excess of what is typically seen in a spray-drying process (up to 80% w/w DM) followed by granulation achieved by back-mixing of finished product and, finally, drying of granules. However, little information is available on how various dairy ingredients behave in this system. Therefore, a novel lab-scale production model was produced to determine limits of superconcentration and granulation behavior of various ingredients. This work provides vital information and represents the first step in a larger program which will culminate in demonstration of the industrial applicability of the new approach for drying of various dairy streams.