During the past couple of weeks, I've been recording the date of shuck-split for several pecan cultivars and the trees in my pecan breeding plot (photo at right is KT149). On the day I find a cultivar at shuck-split, I collect a sample of 30 pecans to be weighed, measured and shelled once the nuts are fully dry.
While collecting these nut samples, I always choose one nut to take a quick look at kernel quality. Using a pair of pruning shears, I carefully cut a nut in half then inspect how well the kernel has filled the inside of the shell.
The photo above shows 5 different selections from my breeding program all collected on the same day. After a very dry summer, I expected to see more poorly filled nuts. However, nut quality ranges from passable to fully packed.
The first thing I notice when looking at a nut in cross section is the width of the interior partition between kernel halves. Note that the nut on the far left has a extremely wide partition and you can see air pockets between the kernel and the outer shell as well as the interior partition. Nuts from this tree will produce kernels that are brittle and dry tasting.
A fully filled pecan (far right nut) packs kernel tissues so tightly inside the shell that it compresses the interior partition into a fine line. You should also note that the kernel is totally solid with no air spaces. The kernels produced by this tree will be dense, richly-flavored and oily.
A nut cross section can also reveal how well packing material is released from the dorsal grooves of a kernel half during the shelling process. In the photo above, I give 3 examples. On the upper surface of each kernel half, you will note the cinnamon-colored packing material that dips down into the dorsal grooves of the kernel. Narrow dorsal grooves can trap the packing material during shelling often requiring manual removal. The flared dorsal groove can also trap packing material especially if the overall shape of the groove is narrow. In making selections for release as new cultivars, I always prefer kernels with wide dorsal grooves. When shelled, these kernels will be completely clean.