Mareike Hunold completed her M.Sc. studies in Food Technology, specialization Food Design, at Wageningen University (WUR, Netherlands). During her thesis she worked on the influence of morphology on the functional properties of dairy protein micro-particles. The mission of the process engineering group at WUR to explore new principles for food production fascinated her and she decided to pursue this path. The work at DMK Group in Germany in Corporate-R&D (Process development department) allows her to combine two professional interests – finding new process opportunities and milk. For two years, she has mainly been working on filtration technologies.
Nanofiltration for acid whey processing
Mareike Hunold, Sven-Rainer Doering and Ralf Zink
Corporate R&D, Group Process-Development (DMK, Deutsches Milchkontor GmbH, Bremen, Germany)
The question concerning the utilization of acid whey rises permanently. The high acid and salt content lowers product quality and causes operational problems in further whey processing. Nanofiltration provides an opportunity to handle the existing large volumes and use of the valuable components present in acid whey. It is a simple, fast and cost-efficient process, whereby partial deacidification/demineralization and concentration can be carried out simultaneously. To maximize lactic acid (LA) and mineral passage without significant lactose loss NF membranes with different molecular weight cut offs and process conditions were tested. The highest selectivity regarding lactose and LA among the tested membranes and an acceptable permeate flux is provided by a 700 Da membrane. A LA rejection of about 37% is obtained, however a decrease in lactose rejection of 10% needs to be tolerated. To achieve an even higher purification the NF-permeate is filtrated by reverse osmosis (RO), so that the RO-permeate can be used for diafiltration. By temperature increase as well as baseline pressure decrease rejection values of all components are reduced to different extents, depending on membrane nature and pore size. Especially, in the low pressure area the influence of the baseline pressure is strikingly. We explain this basically due to a compression of the membrane at higher pB values and favored solvent transmission. By membrane selection and adjustment of process conditions selectivity towards LA and lactose is optimized. However, overall transmembrane flux and thus overall productivity have to be taken into full consideration.
In summary, Nanofiltration provides a feasible and profitable method for partial deacidification / demineralization of acid whey, for its further processing just like regular sweet whey.