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Lotte Juul Knudsen

PhD Student

Lotte Juul Knudsen


PhD project: New lactase enzymes
University: Aarhus University
Department: Department of Food Science
Supervisor: Lotte Bach Larsen, Professor at Department of Food Science
Co-supervisors: Daniel Otzen, Professor at Interdisciplinary Nanoscience Center, Søren Drud Hey-dary Nielsen, Postdoc at Department of Food Science, Valentin Rauh, Arla Foods Innovation Centre.
Project term: 01.05.2019 – 30.04.2022
Master’s degree: MSc in Molecular Biology, Aarhus University


Lactose-free UHT milk has a shorter shelf life (6 months) than conventional UHT milk (9 months), which challenges shelf-life and product distribution for the food industry as well as sensory qualities in relation to consumers. The short shelf-life is linked to a higher reactivity of the lactase generated galactose and glucose as substrate for the Maillard reaction compared to lactose. Moreover, the lactase enzyme preparations have shown to contain unwanted proteolytic side-activity. This proteolytic activity generates free amino terminals and free amino acids, which are the second substrate for driving the unwanted Maillard reactions. Furthermore, the unwanted proteolytic activity can lead to bitter peptide formation and in combination with the Maillard reaction also cause protein aggregation. These unwanted chemical changes results in early product deterioration of the lactose-free UHT milk.


The aim is to characterize new lactase enzymes in relation to unwanted proteolytic side activity, aggregate formation and Maillard parameters in order to improve shelf-life and quality of lactose-free UHT milk.


To investigate the impact of new lactase enzyme preparation on quality of lactose-free UHT milk during storage when added either pre- or post-hydrolysis. Furthermore, the project will elucidate the interplay between chemical reactions, process conditions and enzyme purity. Different mass spectrometry and protein analytical methods will be used to characterize the lactose-free UHT milk.


Arla Foods amba and DSM

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