A new UHT
With a market share of over 70%, UHT milk is the front runner in the German drinking milk market. The popularity can be attributed to its ability to be stored for months at room temperature. However, the heating to temperatures of 135-140°C to make UHT can have some perceived disadvantages. This includes a certain cooked taste of the treated milk and a loss of some nutrients such as vitamins. “It also takes a lot of energy to reach the necessary temperatures and most of it comes from fossil fuels such as oil and gas,” explained Elena Kohler, the student award winner of the Bioeconomy award in Stuttgart. The €2,000 award is given to students at the University of Hohenheim. Germany’s Bioeconomy Science Year is organised by the Federal Ministry of Education and Research.
Kohler is working on combining the advantages of UHT milk and fresh milk through a new production process. Her vision is a new type of milk, combining the advantages of UHT milk and fresh milk: storable at room temperature, with a fresh taste and a high nutrient content.
“The desired product should not only be superior to conventional UHT milk in terms of taste and nutritional physiology. My goal is also a manufacturing process, which is much more energy efficient and therefore ecologically superior to the conventional process,” she summarised.
In Kohler’s concept, milk is divided into two fractions in a novel process: a casein phase, which contains heat-stable milk protein in addition to the unwanted microorganisms, and a whey protein phase, which also contains the heat-sensitive vitamins. As a result, both phases can be heated separately and adapted to the ingredients: quality-reducing substances such as microorganisms and enzymes are rendered harmless in the casein phase by high temperatures. The whey protein phase, on the other hand, is only heated briefly at lower temperatures, so its valuable nutrients and proteins are preserved. After the treatment, both fractions are reunited.
To heat the predominant whey protein phase, the high-energy process in conventional UHT milk is being replaced by energy-efficient microwave technology, whose electricity requirements can be met 100% from renewable energies. Homogeneous heating avoids burning reactions of whey proteins on contact heating surfaces, and less residues form in the equipment, reducing the consumption of cleaning chemicals and the amount of wastewater.
In her master’s thesis, Kohler wants to determine the optimum temperature for the microwave heating of the whey protein phase, which is necessary, on the one hand, to make the milk stable and storable, and on the other hand, to keep product changes caused by heat as low as possible. For quality control, samples of the newly produced milk are stored at room temperature and at 30°C and analysed and compared at regular intervals over three months, with regard to germ content, quality features and their taste.