Phages (viruses that lyse bacteria) can lead to fermentation disturbances and off-flavors in cheese production - especially when the whey produced as a side stream is recycled and added to new batches. Thermal inactivation of phages is undesirable due to strong whey protein denaturation.


In this project, phage reduction by UV-C irradiation of whey in an ADQ-ST1 flow reactor was investigated. The innovative process allows a new whey product with the specification "phage-free" to be put on the market. The company can guarantee increased process reliability and thus gain an advantage in the export of whey products.


Fig.: Test setup for investigating phage reduction in whey.
1: Tank with whey and phages, 
2: Pump, 3: UV-C reactor ADQ-ST1, 4: Sampling.

Bioindicators are applied to directly monitor the success of microbial inactivation. Bioindicators consist of very resistant microorganisms deposited on carrier material. Due to the fact that UV-C technology is less common than thermal processes, there are no bioindicators suitable for UV-C process monitoring available.

Therefore, our goal is to produce bioindicators that have a defined, high resistance against UV-C energy. Above that, those indicators shall be relevant for our customers as a bakery, for example, has to face different microbiological challenges than dairy industry. Depending on the specific demand, in our S2 microbiological lab, we are able to provide bioindicators with mould spores, bacterial spores or even with less resistant vegetative mircoorganisms.

Two of the extremely interesting scientific topics for us are standardization of bioindicators and UV-C treatment of food. In Canada and the USA, UV-C treatment of some carefully selected foods is already allowed and applied. In Europa, many researchers study the possible influence of UV-C on food and the effectivity of UV-C in liquid food against bacteriophages and bacteria. Therefore, we are part of the project committee of three different AiF-FEI products.