Serious damage means any specific defect described in this section; or an equally objectionable variation of any one of these defects, or any other defect, or any combination of defects, which seriously detracts from the appearance or the edible or marketing quality of the individual pecan. The following defects shall be considered as serious damage:

(a) Adhering hull material or dark stains affecting an aggregate of more than 20 percent of the individual shell;

(b) Broken shells when the missing portion of shell is greater in area than a circle one-fourth inch in diameter;

(c) Dark discoloration of the skin which is darker than dark amber over more than 25 percent of the surface of the kernel;

(d) Decay affecting any portion of the kernel;

(e) Insects, web, frass, or the kernel shows distinct evidence of insect feeding on the kernel;

(f) Internal flesh discoloration of a dark shade extending more than one-third the length of the kernel beneath the ridge, or an equally objectionable amount of dark discoloration in other portions of the kernel;

(g) Kernel spots when more than three dark spots on either half of the kernel, or when any spot or the aggregate of two or more spots on one of the halves of the kernel affects more than 10 percent of the surface;

(h) Mold, on the surface or inside the kernel, which is plainly visible without magnification;

(i) Rancidity when the kernel is distinctly rancid to the taste. Staleness of flavor shall not be classed as rancidity;

Note 1 to § 51.1417(i):

Rancidity refers to the tendency of the oil in a pecan kernel to become tainted as a result of oxidation or hydrolysis. Industry measures to determine the tendency of a kernel to become rancid include testing the kernel's peroxide and free fatty acid values. Peroxide values should be less than 5 mEq/kg and free fatty acids acid value should be less than 1 percent. These analyses are not performed in determination of grade.

(j) Undeveloped kernels which are blank (complete shell containing no kernel); and

(k) Worm holes when penetrating the shell.