Concentration of speciality dairy products

Worldwide requirements for high quality, functional, protein-based ingredients have generated increased demand for dairy proteins. In the majority of cases, dairy proteins are concentrated and dried to provide stable, easily transportable products.

Major dairy protein products that are processed by the Centritherm® evaporator include:

• Milk Protein Concentrate and Isolate (MPC and MPI)
• Whey Protein Concentrate and Isolate (WPC and WPI)
• Colostrum
• “Special Proteins” that are ‘sticky’ or high viscous

Prior to the spray drying step, dairy proteins are typically concentrated using membrane filtration techniques such as ultrafiltration. However, ultrafiltration has limitations in maximum concentrations achievable and imposes restrictions upon the dryer capacity and throughput.

Traditional multiple-effect dairy evaporators are not effective in the concentration of dairy proteins due in part to a reduction in protein functionality and handling difficulties. The use of the Centritherm evaporator allows higher concentrations to be achieved and can also substantially increase dryer capacity.

Protein concentrates produced by the Centritherm evaporator are of extremely high quality. This is due to the short residence time (1 second) and low temperatures (typically 45-50o C) that the proteins experience when processed through the Centritherm evaporator. In fact, protein solutions may be concentrated by the Centritherm with no reduction of protein functionality.

Key benefits of the Centritherm include:

• No reduction of protein functionality
• Low hold-up volume (only a few litres even in our largest model)
• Exceptionally short product residence times (about 1 second!)
• Low operating temperatures (around 50°C)
• Negligible thermal impact resulting in high quality concentrate
• Reduced fines
• Increased dryer capacity
• Lower overall energy requirements

Centritherm evaporators have been installed for the production of quality, concentrated dairy proteins around the world.

No Reduction of Protein Functionality
In the Centritherm evaporator, the action of the spinning cones reduces the contact time between the heating surface and the protein solution to approximately 1 second.

Due to the heat sensitive nature of dairy protein solution, these conditions may be adjusted to reduce the temperature difference and further minimise the thermal impact. Lower operating temperatures, such as an evaporation temperature of 40°C and a steam temperature of 70-90°C, are not uncommon.

Unlike concentration in traditional evaporators, no reduction of protein functionality occurs during concentration in the Centritherm evaporator.

High Viscosity Processing
Even at relatively low concentrations dairy proteins can be quite viscous, making complete coverage of the heating surface difficult. In conventional evaporators, this is overcome by maintaining a high flow rate. To achieve the required target concentration and maintain acceptable flow rates requires high levels of product recycle. As a result, traditional evaporators have a longer residence time that gives rise to thermal degradation of the proteins resulting in a noticeable loss of functionality.

The Centritherm evaporator uses centrifugal force to ensure that the protein solution is evenly distributed across the heating surface. In fact, the thickness of the product film inside the Centritherm can be reduced to just 0.1 mm. This centrifugal force also allows higher concentrations to be achieved as unlike traditional evaporators viscosity does not become a limitation.

Increased Dryer Capacity
Throughput for a spray dryer with a fixed drying rate may be substantially increased through the use of a Centritherm evaporator.

Consider the use of a Centritherm in the production of WPC80. WPC powder is made by drying the retentate from the ultrafiltration (UF) of whey. The maximum solids concentration achievable by UF is normally less than 30%. The retentate is then fed to a spray dryer.

Alternatively, a Centritherm evaporator may be used to increase the concentration of the spray dryer feed. The Centritherm can readily concentrate WPC80 from 28% to >40% total solids in a single pass. Greater concentrations are possible depending on flow rates required and concentration of WPC leaving the ultrafiltration system.

In addition to increased throughput, other process benefits are achieved by feeding a more highly concentrated material to a spray dryer. These include increased bulk powder density (and hence better packing) and reduced production of fines.

Fabrication to Dairy Standards
Centritherm evaporators intended for dairy applications are designed and built to comply with strict industry standards. Special consideration is provided to ensure hygienic design and Clean-In-Place (CIP) capabilities. Moreover, specific design requests to meet end user’s internal standards can be taken into account as required.

A range of Centritherm evaporator models are available for batch or continuous processing.

Click here to find out more about the Centritherm® evaporator .