Corn wet milling: separation chemistry and technology

Corn wet milling is a complicated, large-scale, and efficient industrial process designed to separate the chemical components from corn kernels. The success of wet milling, in terms of maximum yields, is largely dependent on the success of the steeping process. Improper steeping, or steeping of corn kernels that have unusual physical or chemical structures, results in lost product and lower profits. Steeping processes, however, are still based largely on an art that was developed more than 100 years ago. In the next 20 years, major seed corn producers expect that the market for corn with unique starch characteristics and corn bred to produce speciality chemicals or have an altered composition will expand substantially. As the market increases for speciality corn, corn genetically bred with unique starch charcteristics or corn with altered chemical composition, a thorough scientific understanding of steeping chemistry and the entire wet milling process will become increasingly important.

Platelet nanocrystals resulting from the disruption of waxy maize starch granules by acid hydrolysis

Colloidal aqueous suspensions of starch nanocrystals were prepared by submitting native granules from A-type amylopectin-rich waxy maize to a hydrochloric acid hydrolysis. The insoluble residue contains polydisperse and more or less individualized platelet nanocrystals corresponding to the lamellae formed by the association of amylopectin side branches into parallel arrays of double helices. After 2 weeks of hydrolysis, 5-7 nm thick lamellae still connected by alpha(1-->6) linkages were seen edge-on using transmission electron microscopy. As the hydrolysis progressed up to 6 weeks, more alpha(1-->6) branching points located in the inter-lamellar areas were severed and the platelets were thus observed in planar view. Despite a variety of shapes, characteristic geometrical features of the nanocrystalsa were recognized, such as marked 60-65 degrees acute angles and constituting parallelepipedal blocks with a length of 20-40 nm and a width of 15-30 nm. X-ray and electron diffraction showed that these nanoplatelets retain the crystalline A-type of the parent granules.