Pilot-scale production of conjugated linoleic acid-rich soy oil by photoirradiation.

Conjugated linoleic acid (CLA) is found naturally in dairy and beef products at levels of 0.2% to 2% of the total fat. A more concentrated source of dietary CLA, low in saturated fat, would be highly desirable to obtain optimum CLA levels of about 3 g/d. We recently reported photoisomerization of soy oil with iodine catalysis to be a simple way of producing CLA in laboratory without high-energy input or expensive enzymes and microorganisms. However, a long irradiation time of 144 h has been a limitation for this technique to be of practical value. The objectives of this study were to build a pilot plant unit to rapidly produce high-CLA soy oil by photoirradiation and optimize the processing parameters to obtain high-CLA soy oil. Degassed oil with dissolved-iodine catalyst was irradiated by UV lamps in an illuminated laminar flow unit (ILFU). The ILFU consists of 2 borosilicate glass plates in a silicone lined stainless steel frame. The static mode of operation yielded 5.7% of total CLA isomers and performed twice as well than the continuous mode with 2.5% of total CLA. Irradiating oil in a static mode with reflective surfaces increased the CLA yields 3-fold to 16.4%. About 22% of total CLA isomers can be rapidly produced from soy oil linoleic acid with 0.35% iodine catalyst in a 0.5-cm-thick oil layer maintained at 48 degrees C for 12 h. The peroxide value and GC-MS analysis did not identify any volatile compounds characteristic of lipid oxidation. This study is a definitive step toward the commercialization of large-scale production of CLA-rich soy oil.