Aarhus University Seal / Aarhus Universitets segl

Control of Bacillus cereus in refrigerated products - Characterization, diversity and spore heat resistance of psychrotolerant strains

PhD defence, Thursday 20 January 2022. Doreen Jepngetich Metto

2022.01.20 | Helle Mitzi Thomsen Reichl

Doreen Jepngetich Metto

During her studies, Doreen Jepngetich Metto researched the psychrotolerant strains of the food borne pathogen Bacillus cereus. Psychrotolerant B. cereus strains form spores that survive heat treatments used for minimally processed refrigerated products, and can grow during refrigerated storage. During her studies, Doreen Jepngetich Metto characterized and studied the diversity, including variability in spore heat resistance, and the growth response of these psychrotolerant strains to the combined effect of temperature, acidic conditions and organic acids. Furthermore, using whole genome sequencing, she investigated the relationships between psychrotolerant phenotypic characteristics and selected genetic markers related to psychrotolerance.


The new research findings contribute to the understanding of the characteristics and diversity of psychrotolerant B. cereus strains, which could be applied for analysis, definition and, in designing heat processes and product formulations, for their control in minimally processed refrigerated products.  


The PhD study was completed at the Department of Food Science, Faculty of Technical Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Thursday, 20 January 2022 at 13.00
Place: The defence is held online. To receive a link to the event, please send an e-mail to Sarah L. Nielsen: sn@food.au.dk  
Title of PhD thesis: Control of psychrotrophic Bacillus cereus in chilled dairy products

Contact information: Doreen Jepngetich Metto, e-mail: doreenmetto@food.au.dk, tel.: +45 50379023

Members of the assessment committee:

Professor Monika Ehling-Schulz, Department of Pathobiology, University of Veterinary Medicine, Austria

Professor Frank Devlieghere, Department of Food Technology, Safety and Health, Ghent University, Belgium

Associate Professor Jette Feveile Young (chair), Department of Food Science, Aarhus University, Denmark

Main supervisor:
Associate Professor Marianne Hammershøj, Department of Food Science, Aarhus University, Denmark

Co-supervisors:
Dr. Anne Elsser-Gravesen, ISI Food Protection ApS, Aarhus, Denmark

Research Scientist Elissavet Gkogka, Arla Innovation Centre, Arla R&D, Denmark

Senior Research Scientist Yinghua Xiao, Arla Innovation Centre, Arla R&D, Denmark

Language: The PhD dissertation will be defended in English


The defence is public.


The PhD thesis is available for reading at the Graduate School of Technical Sciences/GSTS,

Katrinebjergvej 89F, building 5132, 8200 Aarhus N.

PhD defence
17427 / i43