Concentrating milk at the farm – Keeping the high quality

PhD defense, Wednesday 30 August 2017, Ida Sørensen.

2017.08.30 | Steffi Hjerrild Iversen

Ida Sørensen

Ida Sørensen has during her studies worked with milk quality when membrane filtration is moved from e.g. cheese dairy to dairy farm. The rationale behind mowing the concentration to the farm is the possibility of saving CO2 and transport costs by removing part of the water from the milk. The technology is widely used at dairies, but the impact on the milk – especially unpasteurized whole milk – lacked documentation. Thus, the studies of Ida Sørensen focused on assessing the quality of raw milk retentate and how the membrane filtration might influence further processing of the raw milk retentate into e.g. cheese and milk powder. Moreover, this study aims to understand how different processing factors associated with spiral wound ultra-filtration (UF) and reverse osmosis (RO) will affect the retentate quality, and whether concentrating milk at the farm will influence further processing at the dairy.

The results indicate that concentrating milk at the farm does not severely impair the milk quality, neither by mechanical stress or by enzymatically reactions from somatic cells and microorganisms. Filtrating at low temperature (4°C) results in a significant lower lipolysis and proteolysis compared to filtrating at 10°C. Moreover, total bacterial count did not increase more than the concentration factor. Whole milk powder production and storage stability was not influenced by pre-concentrating milk at the farm compared to powder made from regular raw milk. The results showed that concentration of the oxidation products hexanal, heptanal and nonanal increased during storage of both retentate powder and powder from non-concentrated milk, but not to a higher extent than in commercial powder of similar storage. The RO retentate exhibits good rennet coagulation properties, but displays changed behavior towards first and second phase of the coagulation process – possibly due to changed ionic balances.  

The PhD degree was completed at the Department of Food Science, Foulum, Science and Technology, Aarhus University.

This résumé was prepared by the PhD student.

Time: Wednesday 30 August 2017 at 13.00
Place: Auditorium, Aarhus University Foulum, Blichers Allé 20, 8830 Tjele
Title of dissertation: Quality and utilization of raw milk retentate produced at the dairy farm
Contact information: Ida Sørensen, e-mail:, tel.: +45 25327486
Members of the assessment committee:
Associate professor Monika Johansson, Department of Molecular Sciences, Swedish University of Agricultural sciences
Vice President Alexander Tolkach, Cheese Applications, Saputo, Canada
Senior researcher Niels Oksbjerg (chair), Department of Food Science, Aarhus University
Main supervisor:
Associate professor Lars Wiking, Department of Food Science, Aarhus University
Professor Lotte B. Larsen, Department of Food Science, Aarhus University
Language: The PhD dissertation will be defended in English

The defence is public.
The dissertation is available for reading at the Graduate School of Science and Technology/GSST, Ny Munkegade 120, building 1520, rooms 128-134, 8000 Aarhus C.



PhD defence
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Revised 23.02.2018