Hard science and haute cuisine
Molecular restaurateurs juggle proteins and polymers / Neue MaxPlanckResearch published
A physicist at the Max Planck Institute for Polymer Research in Mainz elegantly combines his research on soft matter with cooking as a science. For the "molecular restaurateur" Thomas A. Vilgis, the kitchen therefore becomes a laboratory. Vilgis visited the latest edition of MaxPlanckResearch (4/2003) and describes what happens when "hard science" meets "haute cuisine".Why does meat tenderize when it is cooked, but into a tough shoe sole when it is heated for too long? What happens when whipping egg whites or clarifying butter? Scientists who call themselves "molecular restaurateurs" deal with such questions about the chemistry and physics of roasts, sauces or puddings. Thomas Vilgis is one of them. He is a full-time researcher at the Max Planck Institute for Polymer Research in Mainz, researching the properties of polymers, biopolymers and the complex materials that can build them up.
Fig. 1: The microscopic image of egg whites clearly shows that the walls of the air bubbles are structured like sandwiches: The surface-active protein layers are in direct contact with the air, with the aqueous phase embedded in between.
Image: MPI for Polymer Research
Emulsions, suspensions, foams, gels, biological membranes or fibers consist of very large molecules. These molecules, often polymers, interact across many size scales, ranging from nanometers (billionths of a meter) to micro- or even millimeters. This gives all these materials complex and at the same time characteristic properties. That is why scientists today group them together under the generic term "soft matter", which stands for a diverse and very dynamic field of research. Soft matter includes all biological materials - except for the biominerals in bones and teeth - and therefore everything we eat.
An interesting approach to cooking, for example, comes from the perspective of proteins, i.e. proteins. These biopolymers are large molecules made up of thousands of atoms. In living organisms they play a central role in practically all biochemical processes. The decisive factor here is that these molecules can change their shape - and thus also their biological function: Some proteins can switch between a sheet-like folded shape and a helical helix. According to current knowledge, such processes even trigger brain diseases such as BSE.
Fig. 2: View of the shape of a partially "unwrapped" protein model molecule at various magnifications. Left: The highest magnification shows the primary structure with individual atoms only 0,1 to 0,2 nanometers (billionths of a meter) apart. Here you can see the amino acids that chain together as the basic building blocks to form the protein. The function of the protein and its secondary structure (middle) depend on their order: This can consist of different elements such as helices or folded sheet structures. The secondary structure eventually tangles into the globular, spherical tertiary structure of the complete molecule, which is biologically active (right).
Image: Helmut Rohrer
Thomas A. Vilgis and his team are developing new mathematical models to better understand how antibodies and enzymes work, for example. As catalysts, enzymes accelerate biochemical reactions in the organism, which is what makes many life functions possible in the first place. However, certain enzymes can also help with cooking, for example as "meat tenderizers". In order for biological tissue to be firm and elastic at the same time, collagen fibers run through it. These biopolymer fibers consist of a very stable molecular triple helix - but this makes the raw meat tough. Heating or the action of certain enzymes, for example from the juice of fresh pineapple or figs, can transform the collagen: the triple helices dissolve and the polymers are linked to form a loose spatial network. This creates a gel and the meat becomes tender.
The kitchen offers a variety of complex materials - and thus plenty of fodder for the scientific curiosity of molecular restaurateurs. Interfaces, for example, are of great interest: in food they usually consist of a layer of ordered proteins just a few nanometers thick. Such layers can, for example, connect water and fat droplets that would otherwise repel each other. This creates emulsions like milk and butter. Molecular interfaces also give the air bubbles in foams sufficient stability. To do this, the protein molecules, which are present as balls in the egg white, must first be "unwrapped": This is done by beating with a whisk. The transparent egg white becomes opaque egg white. The altered protein molecules can now enclose the egg's water molecules in fine, sandwich-like membranes. These membranes form a stable shell around the air bubbles in the egg foam. It is amazing that a device as crude as a whisk can change the shape of molecules just a few nanometers in size. So nanotechnology has a long tradition in the kitchen!
MaxPlanckResearch 4/2003 has now been published. The 76-page booklet provides exciting and understandable reports from the institutes of the Max Planck Society. This issue focuses on "optical horizons": The microscope is 400 years old - and still not exhausted. Experience the sophisticated methods with which scientists today travel into the world of the smallest and very smallest and what fantastic insights they gain in the process. The essay poses the question "How much brain does intelligence need?", the Research & Society section ("Numbers games - illusions of certainty") gets to the bottom of the causes of errors in reasoning and misjudgments, and first-hand knowledge is dedicated to the models of the effect of environmental chemicals. Other articles in the issue: "The great communicator" (for Konrad Lorenz's 100th birthday) and "SUSY with the Benedictines" (an unusual meeting of physicists in the Maria Laach monastery).
MaxPlanckResearch is published four times a year. The science magazine can be subscribed to at the press office of the Max Planck Society or via our web form. The subscription is free.
Related Links:
[1] Max Planck research on the internet: http://www.mpg.de/
Original work:
N. Lee, TA Vilgis - Single chain force spectroscopy - reading the sequence of HP protein models - Eur. Phys. J.B 28, 415 (2002)
N. Lee, TA Vilgis - Preferential adsorption of hydrophobic-polar model proteins on patterned surfaces - Phys. Rev E 67, 050901 (2003)
E. Jarkova, N. Lee, TA Vilgis - Swelling behavior of responsive amphiphilic gels - J. Chem. Phys. 119, 3541 (2003)
Source: Mainz [ mpg ]
