| Conjugated linoleic acid (CLA) is a group of geometrical and position isomers of linoleic acid that has been shown to have anticarcinogenic, antiatherosclerotic, antiobesity, immune system enhancement effects. Human intake of CLA from natural sources, dairy (0.55% total fat) and beef (0.60% total fat) is around 10% of the suggested recommended value. However, any increase of beef or dairy products, to increase dietary CLA, would also significantly increase the levels of saturated fats in the diet. Studies show that photoirradiation can be used to synthesize CLA in soy oil with an iodine catalyst. However, the long irradiation time and low CLA yields limit the use of such a technique on a commercial scale. The goal of this dissertation was to develop a state-of-the-art photoirradiation pilot plant scale system to rapidly produce CLA-rich soy oil in large quantities. The objectives were to develop a customized lab scale photoirradiation unit to produce large quantities of soy oil CLA and determine the kinetics of CLA isomerization reactions, develop CLA-rich food products as a carrier of CLA in human diets, develop a pilot scale processing unit and optimize the processing parameters, and study the effect of degree of refining on CLA yields and oil oxidation during photoirradiation.;Soy oil CLA was readily incorporated into potatoes during frying and found to be relatively stable at frying temperatures. A one-ounce-serving of CLA-rich potato chips contained ∼2.4 g CLA, as compared to 0.1g CLA in 3-oz-serving of steak fillet and 0.06 g CLA in 8-oz-serving of whole milk. The peroxide value of the oil extracted from potato chips was found to be 1 milliequivalents/1000g sample which was within the acceptable commercial standards.;The pilot plant static mode of operation yielded 5.7% total CLA isomers and performed twice as well than the continuous mode with 2.5% total CLA. Irradiating oil in a static mode with reflective surfaces increased the CLA yields three-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°C for 12 h. The peroxide value and GC-MS analysis did not identify any volatile compounds characteristic of lipid oxidation.;The study of effect of degree of refining on CLA yields during photoirradiation suggested that refined, bleached, and deodorized (RBD) soy oil gave the highest total CLA yield of 16.3% of total oil with 4.3% cis-, trans-/trans-, cis-isomers. Weight gain studies, as an indication of oxidative stability, indicated that iodine addition decreased the induction time of soy oil samples by 2--4 days. Photoirradiation processing further decreased the induction time by 2 days as a result of loss of tocopherols. Thus, in a refining setup soy oil should be alkali-refined, bleached and deodorized and then photo-processed followed by a secondary adsorption step to remove iodine catalyst to obtain a RBD CLA-rich soy oil.;The lab scale unit produced 22% total CLA in 144 h in presence of 0.15% iodine catalyst and showed that distance between irradiation source and oil, light exposure, and iodine concentration affect the CLA yields. The kinetics study showed that the consumption of linoleic acid (LA) to form cis- , trans-/trans-, cis-CLA was found to be of second order with a rate constant of 9.01 X 10-7 L/mol sec and the rate determining step. The conversion of cis-, trans-/trans-, cis-CLA isomers to trans- , trans-CLA isomers was found to be first order with a rate constant of 2.75 X 10-6 sec-1 . However, formation of thermodynamically stable trans-, trans-CLA isomers (C) with respect to C was a zero order reaction with a rate constant of 10.66 X 10-7 mol/L sec.;This dissertation gives an overview of a commercially viable photoirradiation technique to produce CLA-rich soy oil. |
