Can we break molecules

Molecules on the tongue

How physics researches food

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© Amalia Lopez - Latte Design
© Amalia Lopez - Latte Design

Eating out with Thomas Vilgis is a special experience. The question of how mouthfeel, taste and aromas are created is quick and easy. What happens when you chew? How do structures from large molecules break up and release aromas? One learns from the Mainz physics professor and Max Planck researcher: The properties of food are directly linked to the nanoworld of the molecules. An astonishing amount of physics plays a role in this. However, cheese, pasta, chocolate, vegetables or meat are quite complex materials. In their research, however, physics can display one strength: skillful simplification. This enables them to break down complex foods into understandable basic elements.

Molecules determine the difference between a tender and a chewy fillet, the melting of chocolate and many other physical properties of food. This is what Thomas Vilgis ‘research area is all about "Food Physics", the physics of eating. His team conducts research at the Max Planck Institute for Polymer Research in Mainz. Does it cook in the laboratory too?

This question makes Birgitta Zielbauer laugh. “Unfortunately not,” she replies: “We eat in the cafeteria like everyone else.” The doctor of physics is a laboratory manager in the team and an expert in unraveling molecular processes. To do this, Zielbauer and their teammates use a wide variety of laboratory methods. These include microscopic techniques, for example, which can use X-rays, electrons and neutrons to make individual molecules visible. “We have almost all of these methods in-house,” enthuses the experimental physicist. However, a good theory is required to correctly interpret the results of the experiments.

Let's take a look at some of the basic components of food: Our bodies need proteins for muscle growth, for example, and they also provide energy. In addition, there are pure energy storage molecules, such as the carbohydrates sugar and starch, which plants produce through photosynthesis. Most of the usable energy is stored in fats. Depending on its composition, one gram of fat can have a "calorific value" of up to 40 kilojoules1. The calorific value describes the energy that our body's metabolism can obtain from a substance. Carbohydrates and proteins amount to around 17 kilojoules per gram, and alcohol (ethanol) even to almost 30 kilojoules.

Largely indigestible fiber only has a small amount of usable energy. But they literally give us a bite. This includes cellulose, the tear-resistant fibers of which give the plant cells support. Collagen has a comparable function in animal tissue. It forms a very stable network. Such giant molecules make some raw food tough, difficult to chew and digest. The ingenious solution for this is cooking. Higher temperatures can break down the tough molecular networks, make them soft and therefore easier to digest. With the discovery of fire, our ancestors were able to develop new sources of food. The Mainz-based company used pork fillets as an example to investigate what exactly cooking does.