SCHOOL BREAKS 25-8
In cooking recipes, the hobby chef repeatedly discovers mysterious instructions such as "Add two egg yolks to the cheese sauce with constant stirring." Why in pairs? And why not all at once when you are in a hurry? Such questions were asked by French researcher Hervé This when he read the instructions for a Roquefort soufflé in a women's magazine. Since then, the chemist and foodie is on the trail of superstition in the kitchen and seeks scientific explanations for proven cooking techniques. The Christmas menu is a special scientific challenge for this. The molecular gas astronomer is looking for the best methods for a juicy, tender and aromatic holiday roast. In addition, healthy side dishes should not be missing. For example, the American Chemical Society recommends cranberry sauce for frying. Substances in the red berry defuse aggressive oxygen molecules, which arise when "burning" the food. Thus, the garnish protects the body after the luscious meal. For dessert, the company proposes blackberry or raspberry cake. The berries lower the blood cholesterol level and thus protect against a heart attack. But even the preparation of the roast is an art. The most famous heresy in the field comes from the German chemist Justus von Liebig. The researcher announced in the mid-19th century that meat had to be seared to close the pores and thus retain the juice. This explanation is wrong, This said the science magazine "picture of the science". "If you put a fried steak on the plate, immediately collects a small juice pool, " says the researcher. This simple observation shows that when fried, no water-impermeable crust is formed.

The spicy searing of the Christmas goose is nevertheless important for a tasty roast. At temperatures above 140 degrees, the membranes of the muscle cells on the surface break down. In this way, the sugar molecules contained in the meat combine with proteins to the delicious brown crust. By the way, many volatile aroma substances split off, which give the roast the typical taste. This so-called Maillard reaction - named after its discoverer, the French biochemist Louis-Camille Maillard - is extremely important for cooking and baking. The principle is also behind the irresistible smell of freshly baked bread rolls. The crispy brown crust is particularly fast in dry air. If you prefer a lighter turkey, you should cover it with a foil, advises American nutritionist Sara Risch. This increases the humidity and the speed of the Maillard reaction decreases. For this reason, food in the microwave will not turn brown: the air is too humid. The cooking time of the roast should be kept as short as possible, writes This in his book "Rätsel der Kochkunst - Naturwissenschaftlich Erklärung". This keeps the meat juicy. But you should not take the goose out of the oven too soon. The proteins of the connective tissue, which make the meat tough, dissolve only after a long time, explains This. At temperatures of at least seventy degrees, the protein web of collagen fibers then breaks down into edible gelatin molecules. These pull through the meat with a dense network that holds back the liquid: The roast becomes juicy and "melts on the tongue".

The molecular gas astronomer accelerates this process with collagen-decomposing juices from papaya, pineapple and figs. Already the natives of Mexico wrapped their meat in papaya leaves. But the marinades and fruit juices penetrate only slowly into the connective tissue. This helps with the "medical trick": He injected with a hypodermic pineapple juice directly into the interior of the Christmas goose.

With its biochemical and physical methods, This has already improved many a traditional recipe. So he beats in the preparation of mayonnaise all professionals. These can make about one liter of mayonnaise with one egg yolk. This makes 20 egg out of an egg. He found out that the egg ingredient lecithin can bind much more water than previously thought and therefore it dilates its mayonnaise with liquid. However, the researcher has not yet come to his first riddle: the Roquefort soufflé. In several attempts, he has reviewed the recipe and always came back to the conclusion that the original instructions provide the best soufflé. But the deeper meaning behind the mysterious information has remained hidden to this day. Book tips: Hervé This puzzle of culinary art - Piper explained in 1998 DM 17.90 Peter Barham The Science of Cooking Springer-Verlag 2001 DM 74.77 (only available in English, cooking from the point of view of a physicist) Display

Heike Heinrichs

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