October 28, 2014

   

New study may help milk companies cut energy costs

 

 

Researchers at the Technische Universität München (TUM) in Germany are close to finding a way to help milk companies cut energy costs.

 

By combining different membrane separation processes, they have reduced the amount of energy required in concentrating milk by about 20%.

 

Powdered milk is manufactured using an energy-intensive process chain that involves concentrating and drying milk.

 

Almost half of the milk produced in Germany, or about 830,000 tonnes, is turned into milk powder every year. And about 25% of the energy consumed by the milk industry is used in the production of powdered milk and whey.

 

TUM researchers have been looking at ways of saving energy at the different process steps in the powder production chain.

 

During this process chain, milk and whey are initially concentrated to about 10% of their original volume. In addition to using the conventional method of heating and evaporating the dairy products, the industry also deploys membrane separation processes such as reverse osmosis and nanofiltration. The remaining water in the concentrate is then removed by drying. Despite the very small amounts of water left at this stage, drying can account for 50% of the entire energy consumption bill.

 

Prof. Ulrich Kulozik from the TUM Chair of Food Process Engineering and Dairy Technology and his team have been able to solve this problem by combining three different membrane separation processes: ultrafiltration, reverse osmosis and nanofiltration.

 

Researchers first use ultrafiltration to remove proteins from the liquid. The dissolved constituents can then be concentrated using reverse osmosis and nanofiltration.

 

Removing the proteins in this way speeds up reverse osmosis and nanofiltration by a factor between two and five. This combination of reverse osmosis and ultrafiltration is 20% more energy efficient than reverse osmosis on its own. The proteins and dissolved constituents can be recombined at a later stage in the process chain.

 

The TUM team was also able to double the amount of dry matter produced by cascading ultra- and nanofiltration processes in series.

 

"We were able to show that the right combination of membrane separation technologies can unlock significant efficiency gains in powdered milk and whey production," Kulozik said. "Our aim here is to obtain the highest possible concentrations of milk before evaporation and drying."

 

As to the shelf life of milk concentrates, they can only be kept fresh for a maximum of ten days – until now. The researchers at TUM are also looking to extend this storage period. "We are exploring various heating processes for concentrates with a view to extending the shelf-life for milk concentrate so that it becomes an attractive alternative to powder in the future," explained Prof. Kulozik.

 

The researchers have been able to store concentrates with 30% dry matter content for several weeks at a time at temperatures below 10 degrees Celsius without impacting on the product quality.

 

"One of the main benefits of concentrates is that they are still liquid and so they do not need to be dissolved in water again," said Prof. Kulozik. "And because there is no drying process involved, they also deliver significant energy and cost savings."

 

Prof. Kulozik's team is collaborating with Prof. Martin Grunow, chair of Production and Supply Chain Management, to examine the benefits of concentrates.

 

They are evaluating the value potential of concentrates relative to powders, and also assessing the market needs and logistics required within the industry. The spotlight is on sustainability and climate footprint and the teams will be using ecological balance software to measure the performance of the different technologies.

 

Two companies from the dairy industry are also working with the TUM teams on this subproject.