Linoleic acid is the primary chemical component responsible for oxidation and rancidity in pecan kernels. Linoleic acid varies widely in different varieties of well-matured and plump kernels, and it also varies from year to year in the same variety. Lowering the moisture content of pecan kernels is an important step for maximum storage life of pecans. Pecans, like many other agricultural products, are harvested at moisture contents higher than those required for storage. Water content decreases in pecans harvested later in the season.
Pecan moisture needs to be decreased as soon as practical after harvesting.
This prevents molding, discoloration, and breakdown of the oil. Drying pecan nuts was originally done outdoors, by air and sun drying. This process took three to four weeks and molding often took place in the pecans. Artificial drying or drying with forced air is now used for pecans, speeding up the process considerably and eliminating molding problems. In-shell pecan kernels will darken under high humidity as a result of the tannic acid being dissolved from the shell lining.