The inspection and grading of peanuts by the Agricultural Marketing Service of the U.S. Department of Agriculture (USDA/AMS) occurs at buying stations or shelling plants usually located within a few miles of where the peanuts have been harvested. A pneumatic sampler withdraws a representative quantity of peanuts from the drying wagon, and from this sample the USDA inspector determines the meat content, size of pods (for Virginia &Valencia), damaged kernels, foreign material, and kernel moisture content. Once the grade is established, the loan or commercial value is determined from USDA price support schedules.
After grading, peanuts move on to the shelling process. In the first step of this process, peanuts are cleaned -- stones, soil, bits of vines and other foreign materials are then removed. The cleaned peanuts move by conveyor to shelling machines where peanuts are de-hulled as they are forced through perforated grates. The peanuts then pass through updraft air columns that separate the kernels from the hulls. Specific gravity machines separate the kernels and the unshelled pods. The kernels are then passed over the various perforated grading screens where they are sorted by size into market grades.
The edible nuts are individually inspected with high-speed electronic colour sorting equipment that eliminates discoloured or defective kernels as well as any remaining foreign material.
Inshell peanuts are usually produced from large Virginia or Valencia type peanuts that have been grown in sandy and light-coloured soil for bright hulls. Sizing screens remove the small pods while updraft air columns remove very immature and lightweight pods. The largest remaining pods are separated into size categories by screens. Stems are removed and any remaining immature pods are removed by specific gravity. Electronic sorters then remove dark, cracked, or damaged pods so that only the most mature, brightest pods remain.