Why do fried foods taste so good

French fries: The secret of deep-frying twice

Crispy on the outside and soft on the inside - this is how the perfect fries should be. The deep-fried potato sticks are one of the absolute favorite dishes, and not just for children. But how do french fries get really crispy? At a workshop of the German Society for Fat Science, scientists now explained the complex physical processes involved in preparation and the secret of deep-frying twice. This is what RĂ¼diger Lobitz reports from the aid info service nutrition, agriculture, consumer protection e. V. (aid).

Fat ensures an even transfer of heat

When deep-frying, water-containing foods - in this case potatoes - are baked in hot fat or cooking oil at temperatures of 140 to 180 degrees Celsius. Because fats and oils have a high heat capacity, they can transfer heat to the food at temperatures above 100 degrees Celsius (well above the boiling point of water). The water bound in the food gradually evaporates. In a first phase, according to aid, a thin crust forms within a few seconds, the structure of which has a decisive influence on the further deep-frying process and the quality of the fries in terms of fat absorption and crispness.

First fry pale yellow, then golden yellow

This crust gets its optimal properties when the fries are pre-cooked at low temperatures - around 140 degrees Celsius - until they are pale yellow, reports the consumer association. Then they are removed from the fat and cooled briefly. This is followed by a second deep-frying process at around 175 degrees Celsius. Only when no more water is brought from the inside of the fries to the edge layer does the temperature rise increasingly from the outside to the inside to over 100 degrees Celsius. The typical deep-fried aroma and taste and golden yellow color begin to develop. And that's how they taste best.

The fat must not get too hot

However, a deep fryer should not be set above 175 degrees Celsius. Because starchy foods such as potatoes form acrylamide at the high temperatures that prevail in a hot fat bath - a substance that is considered carcinogenic. In addition, if the temperature is too high, the shell burns before the inside is done.

This is what you need for crispy fries

French fries are quite easy to make from just a few ingredients. You will need potatoes, medium-sized ones are best. Floury varieties are recommended for Belgian fries. These are then cut into thick sticks. If you like the fries firmer, you can take waxy or predominantly waxy varieties and cut the potatoes into thin sticks. The cut potatoes are washed in water until no more starch comes out and the washing water is very clear. Then they are dried thoroughly and then fried twice as described above. In between, the fries are removed from the fat and - ideally on paper towels - cooled down.