How much do you need to knead?
Looking at the science of good breadmaking.
By Nick Carne
You know breadmaking is a serious business when scientists get involved.
Physicists from Germany’s Technical University of Munich have been using 3D computer simulations to study the all-important dough kneading process in the hope of finding better ways to get the timing and the mechanics just right.
Their recipe is published in the journal Physics of Fluids.
During kneading, air is incorporated into the dough matrix, which develops the gluten network that forms the structure of the bread.
It's important not to knead too much, because this leads to a dense and tight dough due to a reduced water absorption capacity that impairs its ability to rise. But do too little, and you’ll decrease the dough’s the gas retention capacity.
Seemingly simple, dough is in fact a complex material whose mechanical properties are somewhere between those of a viscous liquid and an elastic solid, the Munich team says.
"Because of its elasticity, dough overcomes gravitational forces during kneading and moves toward the rotating rod, then climbs up it,” says co-author Natalie Germann. “If you've ever used a kneader or mixer to make dough in your kitchen, you've probably observed this phenomenon."
Germann and colleagues are using 3D computer simulations that consider viscous and elastic properties, as well as the free surface formed between the air and the dough.
They then create computer geometries based on CAD drawings of real industrial kneaders to obtain predictions as close to reality as possible.
These simulations provide essential information about what's happening inside and on the dough's surface over time, such as the incorporation of air into the matrix, and dough pocket formation and breakup.
Germann says previous work considered only the purely viscous properties of the bread dough and restricted simulations to extremely simplified geometries such as a concentric cylinder setup.
Because they didn’t consider the elasticity of the material, she adds, normal stress effects responsible for the rod-climbing phenomenon are absent.
"Our computer simulations showed that vertical mixing isn't as good as the radial mixing in the spiral kneader we considered in our work.
“In the future, mixing performance may be enhanced by using a more highly curved spiral arm or two spiral arms similar to kneading by hand."