# Utilization of the Nutritional Potential of Wheat Bran Using Different Fractionation Techniques
## 3 Variability of Wheat Milling and Technological Potential  
The aim of the standard milling process is to separate the grain outer layers, sub-coat layers, and the germ from the starch endosperm, i.e., to remove the pericarp, the awns, and also the aleurone layer, in order to obtain the white flour used in baking. The standard milling of wheat is a typical example of refining. The desired fraction is extracted from the raw material, in this case the purest possible endosperm alongside by-products, and waste. The aim is, as in any refining process, to extract the maximum amount of the desired fraction with the highest possible efficiency but, of course, while maintaining its quality. The modern milling process of standard wheat processing fully meets this requirement in well-equipped production lines. If the wheat grain contains approximately 80% endosperm by weight, the yield of standard baking and pastry flours also reaches this value [5; 41].  
The basic parameter characterizing baking and pastry flours is the mineral content or ash content. The ash content of bread flours is around 1% (weight % in dry matter of the flour), and the cumulative ash content of all standard baking flours is around 0.65% (weight % in dry matter of the flour), which corresponds to the average ash content of the endosperm. The endosperm is covered by an aleurone layer, but its ash content is many times higher, so the standard milling process needs to lead to its removal if the requirements of standard baking and pastry flours are to be fulfilled. This results in the virtually complete removal of all the layers of grain that may contain nutritionally important fiber components, since these are, as mentioned above, in the aleurone layer and the layers above it [5].  
On the other hand, the layers above the aleurone layer towards the grain surface clearly contain higher and higher proportions of those fiber components (cellulose, lignin, non-extractable hemicelluloses) that are responsible for the deterioration of the technological properties of doughs and the sensory properties of the final products [42; 43].  
There are basically three ways to achieve a substantial increase in the content of desirable fiber components while avoiding undesirable effects on technological and sensory properties [41]:  
1. The use of wholeneal flours containing all the ingredients of the outer layers, but sufficiently finely granulated to minimize their destructive effect on the dough structure. This cannot be achieved with the standard milling process. It is therefore necessary to choose an alternative milling method which achieves fine granulation of the pericarp particles while avoiding deeper destruction of the starch in the endosperm. This requires the use of special milling machines, which are not included in the standard milling process and can also be very expensive.
2. The use of flours that are not wholeneal but contain a substantial proportion of mainly sub-coat layers, where more of the required fiber components and less of the lignocellulosic complex are present. This can be achieved by surface treatment (see below).
3. A third possibility is to classify the bran particles obtained in a conventional milling process (after possible modification of their granulation) on the basis of the different physicochemical properties of the particles with different contents of the substances under discussion.  
Bran obtained by the standard milling process can also be treated without fractionation. Currently, several approaches exist to treat wheat bran without separating any of its components for further use, and some of them have even been patented for the commercial sphere. These are either by modifying the properties of the bran, for example, by extrusion or hydrothermal treatment, or using enzymatic processes or fermentation [21; 22; 23; 44; 45].