Maria A. Karlsson

I'm a PhD student at the department of Molecular Sciences. My project, entitled Stability of UHT milk and the impact of raw milk quality, is a collaboration between SLU, Norrmejerier and Tetra Pak Processing System. In 2016 I was awarded Agronomist of the year for starting Agronomuppropet.


Course responsible for Grundkurs – Livsmedelsagronom, 15 credits, LV0100 (year 2016, 2017, 2018)


I currently investigate how factors related to the composition and properties of raw milk may affect the stability of ultra-high temperature (UHT) milk during storage. The correlation between predictive methods and the stability of UHT milk during storage will also be assessed.


At the dairy, the incoming raw milk is subject to several processes such as separation, homogenisation, heat treatment etc. For liquid products UHT processes can be used to obtain a product with a shelf life of several months when stored at ambient temperature. During the UHT process the product is heated to a temperature exceeding 135 °C for a few seconds. Such intense heat treatment may cause changes in the product during storage such as off-flavour, browning, fat separation, protein aggregation, sedimentation and gel formation. These changes can be derived to the process and storage conditions, but also to the raw milk quality.

In this project we will introduce variation in the milk to study effects on stability using predictive methods. In parallel, correlation between observations in predictive methods and the stability of UHT processed milk during storage will be evaluated. The laboratory work will mainly be conducted at SLU. Through collaboration with a dairy industry partner (Norrmejerier) and process industry (Tetra Pak) the project will have access to pilot and production plants allowing studies on the impact of various parameters on the stability of true products during storage. The ultimate goal is to provide valuable knowledge to help reduce the dairy industry's challenges, and markers that better may predict unfavourable changes e.g. sedimentation, gel formation and fat separation during storage of UHT products.


My PhD project consists of five studies (I-V) with the aim to answer the following research questions:

I. What are the variations in composition of Swedish raw milk and UHT milk? During one year, on a monthly basis, raw milk and the corresponding UHT milk will be collected from Norrmejerier.
II. What is the effect of variation in chemical composition (e.g. calcium, citrate and urea) of raw milk on the stability of the UHT milk during storage?
III. How does variation in the raw milk composition and properties affect the stability of UHT milk during storage?
IV. How well do results from predictive methods correlate with the stability of UHT products during storage? Can a predictive test be used to give an estimation of the quality and stability of the final UHT product?
V. On a microstructural level, what mechanisms cause e.g. sedimentation and gel formation in UHT milk?


High school students
Simon Sundin, Max Börjes Liljesvan, Daniella Zhou
Sofia Pilström, Daniel Larsson, Rikard Larsson, Vigge Ulfsson, Waldemar Åkerskog.

Bachelor student
Johanna Frick

Master student
Eva Edlund Tjernberg

Ellen Steneryd

Master level internships
Felicia Alam
Emma Thorén

Publikationer i urval

Karlsson, M. A., Langton, M., Innings, F., Wikström, M., & Lundh, Å. S. (2017). Short communication: Variation in the composition and properties of Swedish raw milk for ultra-high temperature processing. Journal of Dairy Science, 100(4), 2582–2590.

Poster presentation at 9th NIZO Dairy Conference on Milk Protein Functionality, 30 Sep - 2 Oct 2015, Papendal, Netherlands

Oral and poster presentations at IDF World Dairy Summit, 29 Oct - 3 Nov 2017, Belfast, Northern Ireland

Poster presentation at 21st International Conference on Food Technology & Processing, 4-5 Oct, London UK

Poster presentation at 32nd EFFoST International Conference, 6-8 Nov 2018, Nantes, France