Structure, Composition and Quality of Grain

Mature com or sorghum kernels are unique, well-organized entities that exist for the purpose of reproducing the species. Descriptions of their structures and compositions are helpful in understanding the process of disruption that is achieved during the wetmilling process. 

The corn kernel is a one-seeded fruit classified as a grain,22 borne on a female inflorescence commonly known as the ear. Each ear is comprised of a central stem, the cob, on which up to 1000 seeds develop. The seeds (kernels) mature about 60 days after pollination and are harvested in late summer or early fall (in the northern hemisphere) when kernel moisture content has dropped below 30% (wet weight basis). 

Cellulose + lignin (acid detergent residue) (%, dry basisd) 3.3-4.3 3.3 

The average oil content of commercial com hybrids planted in the com belt has declined over the last 50 years from 4.8-5.0% to 4.4%.52 The apparent cause of this decline has been widespread use of one or two high yielding, low oil content corn inbreds. At the same time, the iodine value of com oil has increased from 122-124 to 128-130, equivalent to a linoleic acid content increase from 55% to 60%. This change is apparently associated with the decline in oil content.53 

Increasing the total protein content of com by breeding has not resulted in development of high protein, commercial hybrids, partly because the use of low or high levels of nitrogen fertilizers can also cause protein levels to vary from 8% to 12%. Furthermore, the increased protein is predominantly zein51,58 which is nearly devoid of two essential amino acids, lysine and tryptophan. 

---

This is the most widely used method for the determination of the phase composition of powders. The x-ray diffractometer contains a source of monochromatic x-rays that irradiate the sample and are diffracted from atomic planes and detected. The angle of diffraction of x-rays by the crystalline planes is characteristic of the crystal structure, and the intensity of scattered radiation is characteristic of the atomic composition. In recent years, automated data processing has enabled higher accuracy and speed. A number of problems are encountered in the quantitative determination of phases in fine powders. Some of these are overlap of phase peaks (e.g., in silicon nitride), orientation of grains, and presence of coarse particles. The last produces distortion of the diffraction data. A number of standard reference materials for XRPD have been developed for use in improving the quality of data [37]. 

Weldability of the material important and combines many of the basic properties that govern the ease with which a material can be welded and the quality of the finished weid, i.e. porosity and cracking. Material composition (alloying elements, grain structure and impurities) and physical properties (thermal conductivity, specific heat and thermal expansion) are some important attributes which determine weldability. 

Phosphorus tends to segregate in poor-quality steels. In rolled steel with too much P, polished and etched sections show distinct bands of metal phosphide ( phosphorus banding ). Very fine grain structure and superplasticity at high temperatures is shown by ferrous alloys with compositions, for example, Fe = 98.6%, Mn = 1.16%, P = 0.5%, V = 0.1%, C = 0.14%. The composition of some typical steels are listed in Table 12.56. 

---