Electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. Sensory and compositional characteristics of low trans soybean oils

Soybean oils were hydrogenated either electrochemically with Pd at 50 or 60 degrees C to iodine values (IV) of 104 and 90 or commercially with Ni to i odine values of 94 and 68. To determine the composition and sensory charact eristics, oils were evaluated for triacylglycerol (TAC) structure, stereosp ecific analysis, fatty acids, solid fat index, and odor attributes in room odor tests. Trans fatty acid contents were 17 and 43.5% for the commerciall y hydrogenated oils and 9.8% for both electrochemically hydrogenated produc ts. Compositional analysis of the oils showed higher levels of stearic and linoleic acids in the electrochemically hydrogenated oils and higher oleic acid levels in the chemically hydrogenated products. TAC analysis confirmed these findings. Monoenes were the predominant species in the commercial oi ls, whereas dienes and saturates were predominant components of the electro chemically processed samples. Free fatty acid values and peroxide values we re low in electrochemically hydrogenated oils, indicating no problems from hydrolysis or oxidation during hydrogenation. The solid fat index profile o f a 15:85 blend of electrochemically hydrogenated soybean oil (IV = 90) wit h a liquid soybean oil was equivalent to that of a commercial stick margari ne. In room odor evaluations of oils heated at frying temperature (190 degr ees C), chemically hydrogenated soybean oils showed strong intensities of a n undesirable characteristic hydrogenation aroma (waxy, sweet, flowery, fru ity, and/or crayon-like odors). However, the electrochemically hydrogenated samples showed only weak intensities of this odor, indicating that the hyd rogenation aroma/flavor would be much less detectable in foods fried in the electrochemically hydrogenated soybean oils than in chemically hydrogenate d soybean oils. Electrochemical hydrogenation produced deodorized oils with lower levels of trans fatty acids, compositions suitable for margarines, a nd lower intensity levels of off-odors, including hydrogenation aroma, when heated to 190 degrees C than did commercially hydrogenated oil.