PhD Defence by Julian Cardini

Principal supervisor:

• Katrin Löschner

Co-supervisor:

• Jens J. Sloth

Examiners:

• Associate Professor Ditte Baun Hermund , DTU FOOD
• Professor Jörg Bettmer, University of Oviedo, Spain
• Researcher Veronika Sele, Institute of Marine Research, Norway

Moderator at defence:

• Senior Researcher Heidi Amlund

Resume
Cadmium is a toxic metal that is found naturally in the environment, but human activities have increased how much of it ends up in soil and crops. Because many plant-based foods can absorb cadmium from the soil, this metal can enter our diet through foods such as beans, grains, vegetables, and other plant products. Food safety assessments usually measure the total amount of cadmium in food, but that does not show how cadmium is actually present inside the food. It can be attached to small natural compounds, to proteins, or to larger structures, and this may affect how it behaves during digestion and how much of it becomes available for absorption in the body.

The aim of this PhD project was to better understand how cadmium is bound inside plant-based foods and what happens to it during digestion. To do this, advanced analytical techniques were used to separate cadmium-containing compounds by size and to identify which types of molecules were associated with the metal.

The results showed that cadmium in plant-based foods is more complex than previously thought. Earlier studies mainly focused on small cadmium-binding molecules called phytochelatins. However, it was found that cadmium is not only linked to small molecules but is also often associated with much larger protein-rich structures. In some foods, these larger structures contained a substantial part of the extractable cadmium.

This project also studied what happens during digestion. Under stomach conditions, cadmium was redistributed from larger structures to smaller ones, likely because proteins are broken down by acid and digestive enzymes. In the intestinal phase, the pattern became more dependent on the type of food. This means that the chemical form of cadmium can change a lot during digestion.

Overall, this work provides a broader understanding of how cadmium exists in plant-based foods. This is important because it may help improve future food safety assessments by looking beyond total cadmium concentration and considering how cadmium is chemically bound in food.

A copy of the PhD thesis is available for reading at the department.