Abstract
Wheat is one of the major crops worldwide. Why does wheat succeed for human food and livestock feed? There are two aspects to its success. One is its environmental adaptability. And the other is the gluten protein fraction which shows the visco-elastic properties that allow dough to be processed into bread, noodles, and other various food products. For the point of view of the first one, as wheat evolved in the desert region of the highland gives ears with awns and the crease on the wheat grains in itself, these unique organs resulted in wide environmental adaptability.
The major components of wheat flour is starch and protein. Wheat starch consists of the lenticular granules of approximately 20μm mean size and spherical granules of approximately 5μm mean size. The granule is organized in concentric alternating semi-crystalline and amorphous layers. The semi-crystalline layer mainly consists of amylopectin. On the other hand, the amorphous layer almost consists of amylose. The amylose is a linear polymer consisting of approximately 1000 molecules of glucose linked by α 1-4 bonding. The amylopectin is a dendritic polymer branched by α 1-6 bonding every 20–25 molecules of glucose. The ratio of the content of amylose to that of amylopectin in starch strongly affects the texture of final food products. Hydrated protein, called gluten, confers the visco-elastic properties. The cross-linking of amino acid residues among domains gives a macro polymer. Because cross-linking is a chemical reaction, the three part requirements of chemical reactions (temperature, space, time) are of importance. In addition, increasing the pH of dough causes the de-amidation of the glutamine and asparagine, and the de-amidation generates glutamic and aspartic acid and ion bonding cross-linking takes place, as a result, the dough becomes hard. The unique properties mentioned above have produced a wide variety of foods such as bread and noodles.
Finally, based on the above findings, this article shows the interesting processing technique of food products, such as the batter of tempura and Japanese thin noodle (somen), which were featured in several television programs in Japan.
