The stain may be brown, black or the reddish discoloration associated with some plant diseases. Smudge is a grading factor when more than one-half of the kernel is discolored or when the discoloration extends into the crease of the kernel. Penetrated smudge - This discoloration penetrates and extends throughout the endosperm and is usually caused by a serious infection of fungal plant disease such as Alternaria. Red smudge - This dark reddish discoloration is most commonly associated with amber durum wheat and usually affects the entire bran portion of the kernel. Discoloration is not superficial and cannot be removed through abrasion.
Soundness refers to overall visual grain quality.
Sound grain is reasonably well matured and reasonably free from kernels damaged by frost, mildew, bleaching or weather staining. Artificial stain - Includes any stain on kernels caused by contact with foreign substances such as dye, or adhered foreign material such as oil, grease, paint, or soot, but excludes any stain caused by poisonous substances. Natural stain - Includes any stain on kernels caused by contact with natural substances such as smut spores, soil or weeds. Samples containing kernels with unusual dark grey streaks on their sides toward the brush may be affected by streak mould. This very slow-growing mould is harmless in wheat, except that it affects kernel appearance.