# Utilization of the Nutritional Potential of Wheat Bran Using Different Fractionation Techniques
## 5 Bran from the Standard Mill Process and Possibilities for Its Fractionation
### Air Screening and Sieving  
Another method that takes advantage of the different physical properties of the packing layers and the different fiber components is the combination of sieving and float grading [41]. This is a combination of sorting by dimensions but also by aerodynamic properties and specific gravity. The use of this method, known as the elusive process, has been most thoroughly described for dried distillery stilage from ethanol production [48]. Similar processes are generally used in grain cleaning plants, but in which different material dimensions are involved. The incoming material is divided into two final parts; the first is enriched with neutral detergent fiber, and the second has more suitable parameters for use as feed than the incoming meat. The neutral detergent fibers are cellulose, hemicelluloses, and lignin. Some components of soluble fiber are not determined by this method, as they dissolve during the determination and are not captured [62]. However, fiber valuesdetermined as neutral detergent fiber and fiber values determined by the gravimetric method correlate strongly with each other for pure wheat products and especially for milling fractions. The first step is to screen the materials through several sieves with progressively smaller meshes. The fractions thus obtained are further separated by elutriation. The particles that are carried by the air stream to the top of the elutriation column are designated as the lighter fraction, and the particles that remain at the bottom are designated as the heavier fraction [63]. This method yields a lighter fraction with a neutral detergent fiber content above 50% and a heavier phase with a reduced neutral detergent fiber content slightly above 30%. Different physical properties of the particles contribute to the difference in the behavior of the different particles in terms of buoyancy. The key ones are density, size, shape, and their combined effects. To optimize the separation, [PERSON] and [PERSON] determined the density of the fiber and non-fiber fraction particles, as well as their equivalent spherical particle diameter, particle sphericity, and terminal velocity [64]. The fibrous particles were also entrained at lower air velocities due to their lower density. The same technique was used for the separation of pericarp particles from corn flour for ethanol production, in which the higher fiber content fraction accounted for nearly 4% of the entering mass and contained over 60% neutral detergent fiber [64, 65]. This method did not appear to be as effective for a mixture of by-products of flour production. The separation factor of the neutral detergent fiber is lower than that of the other intermediates studied [66]. Another study used a slightly different approach and came up with results more interesting for use in human diets. The aim here was not to separate the fiber but to obtain a bran fraction with increased protein content. The bran, after drying to a moisture content of 5%, was ground in an impact mill with a resulting median particle size of 131 \(\upmu\)m. This was followed by air jet sorting. For the lighter fraction, with increased protein content, the insoluble fiber content was reduced. There was no change in the soluble fiber content, which raised the soluble to insoluble fiber ratio from 0.22 to 0.85. This change suggests that, as in the previous study, there may have been a reduction in the content of particles belonging to the pericarp, and thus containing higher levels of cellulose and lignin. The lighter fraction also has a higher ash content than the heavier fraction, which could indicate a transition of particles from the aleurone layer, the outer layer most rich in ash, to the lighter fraction [67, 68]. A combination of milling, sieving, and airflow sorting was used to obtain a fraction of defatted oat bran enriched in \(\beta\)-glucans [69]. In this case, oat bran was defatted, milled in a punch mill, and then airflow sorted by size.