Effect of pro-oxidants on the occurrence of 2-pentyl pyridine in soy protein isolate

Levels of 2-pentyl pyridine in hexane-defatted soybean flours prepared from Burlison, Stressland, and Probst varieties and a variety null for lipoxygenase 1, 2, and 3 were determined using an internal standard of deuterium-labeled 2-pentyl pyridine. These defatted flours contained from 0.06 to 0.51 ppm 2-pentyl pyridine. The flours from lipoxygenase-null and Stressland varieties of soybeans contained the lowest levels. Control freeze-dried soy protein isolates (SPl) prepared from defatted-flours all contained from 0.16 to 0.18 ppm 2-pentyl pyridine. Adding pro-oxidants (FeCl₃, CuCl₃) or exposing the protein slurries to ultraviolet light during SPl processing increased the level of 2-pentyl pyridine in the protein isolates by up to 1256 percent above the control Burlison, Stressland, and Probst SPl. The CuCl₃ and/or UV treatment contributed the largest increase in each case. The same pro-oxidant and UV treatments contributed no significant increases in the level of 2-pentyl pyridine in the protein isolates from the lipoxygenase null SPl.