Kneading
Kneadingis a process in the making of bread or pasta dough, used to mix together the ingredients and add strength to the final product. Its importance lies in the mixing of flour with water. When these two ingredients are combined and kneaded, the gliadin and glutenin proteins in the flour expand and form strands of gluten, which gives bread its texture[1] (To aid gluten production, many recipes use bread flour, which is higher in protein than all-purpose flour.) The kneading process warms and stretches these gluten strands, eventually creating a springy and elastic dough. If bread dough is not kneaded enough, it will not be able to hold the tiny pockets of gas (CO2) created by the leavening agent (such as yeast or baking powder), and will collapse, leaving a heavy and dense loaf.
Kneading can be performed with a breadmaker, a mixer equipped with a dough hook, or by hand. The dough is put on a floured surface, pressed and stretched with the heel of the hand, folded over, and rotated through 90º repeatedly. This process continues until the dough is elastic and smooth. The dough can then be allowed to rise or "prove".
Similar to kneading is knocking back or punching down, which is done to the dough after proving. The dough is punched once or twice, after which it is kneaded gently for a short time. The aim of this is to remove any large air pockets which have formed in the dough, create an even texture in the bread and redistribute the nutrients for the yeast, thus allowing fermentation to continue. The dough can then be proved a second time. Another method of knocking back (also known as "folding") is to gently stretch and pat out the proved dough before folding the sides in towards the centre.
(Wikipedia, Kneading, 11/8/2011)
“Traditionally, a product comprising an incompatible polymer blend has been processed using a kneading-type extruding machine or molding machine. However, the screw rotation speeds of these machines are around 300 rpm at most, and the shear rates achievable at such screw rotation speeds are only around 100 sec.sup.-1. At shear rates of this level, the polymer viscosities or filling material dispersion condition cannot be changed sufficiently during kneading, which makes is impossible to mix the incompatible polymer blend at nano-level or nano-disperse a filling material such as a filler in the resin.” [Shimizu. Li and Zhao, US Patent 8,048,948 (11/1/2011)
Recent US Patents
11/1/2011
8,048,948
Filler-dispersed melt-kneaded products, molded resin products thereof, and production method thereof
Shimizu, Li and Zhao of the National Institute of Advanced Industrial Science and Technology, Japan, developed a melt-kneading method for filling material-containing resin or elastomer includes: a step of preparing a filling material as a filler and a resin or elastomer comprising an incompatible blend; and a step of introducing the filling material-containing resin or elastomer into a material feed part provided at an end of a cylindrical melt-kneading part having a heater and provided with a screw, and then melt-kneading the filling material-containing resin or elastomer under conditions where the rotation speed of the screw is about 600 rpm to about 3,000 rpm and its shear rate is about 900 to about 4,500 sec.sup.-1, thereby forming a co-continuous structure comprising the incompatible blend. (RDC 11/4/2011)