E: Food Engineering & Physical Properties JFS E: Food Engineering and Physical Properties Pilot-Scale Production of Conjugated Linoleic Acid-Rich Soy Oil by Photoirradiation V.P. JAIN, A. PROCTOR, AND R. LALL ABSTRACT: 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 ob- jectives 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 ir- radiated 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 sur- faces 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 ◦ 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. Keywords: commercial, conjugated linoleic acid, photoirradiation, pilot scale, soy oil Introduction C onjugated linoleic acid (CLA) consists of a group of geomet- rical and positional linoleic acid isomers that are bovine ru- men fermentation products, found in dairy and beef food prod- ucts (Chin and others 1992). Several animal studies cite the dietary benefits of CLA, such in suppressing carcinogenic (Pariza and oth- ers 1979) and atherogenic (Lee and others 1994) effects, enhancing the immune system (Cook and others 1993), and as an antidiabetic agent (Ris´ erus and others 2002). Clinical trials by Ris´ erus and others (2001) indicated that CLA significantly reduced abdominal obesity in men with metabolic syndrome. Thom and others (2001) showed that 1.8 g CLA/d for 12 wk reduced body fat in healthy exercising humans. Daily CLA intake from natural sources is typically about 0.3 g. This includes beef (0.6% total fat) (Beaulieu and others 2002), dairy products (0.55% total fat) (Veth and others 2004), and margarine (Carpenter and Slover 1973). To obtain the estimated optimum dietary CLA levels of about 3 g/d (Ip and others 1991), it would be necessary to increase dietary animal fat, which would increase saturated fat intake. Therefore, a concentrated source of dietary CLA that is low in saturated fat would be highly desirable. Mir and others (2004) increased beef CLA by feeding cattle with high grain diets and dietary oil. A maximum of 134 mg CLA/100 g meat was obtained, with the CLA concentrated in intramuscular subcutaneous fat. Bauman (2000) showed that cattle fed with full fat soybeans resulted in 20% increase in the beef CLA. However, this increased value would not provide the daily requirements (Ip and others 1991). Conjugated linoleic acid can be commercially synthe- sized, extracted, and isolated, and linolenic acid can be enriched MS 20070795 Submitted 10/24/2007, Accepted 1/23/2008. Authors are with Dept. of Food Science, Univ. of Arkansas, 2650 Young Ave., Fayet- teville, AR 72704, U.S.A. Direct inquiries to author Proctor (E-mail: aproctor@uark.edu). with CLA content. These products can be in the form of triglyc- erides, fatty acids, or fatty acid esters (Reaney and others 1999). Bromination, dehydration of hydroxyl fatty acids, and other chem- ical methods are associated with low yields, time required for the purification of the intermediates, and inseparability of the isomers by conventional methods (Adlof 1999). Enzymatic interesterifica- tion may be a practical method to synthesize CLA isomers in triglyc- eride oils. However, lipase-catalyzed interesterification resulted in high levels of oxidation of the oil and low yields of CLA (Lee and others 2003). Most CLA synthesis studies have been done by inter- esterifying methyl esters, which are not applicable to food systems (Lee and others 2004). Jain and Proctor (2006) reported a simple way of producing high levels of CLA in soy oil without high energy input, expensive en- zymes, or microbial fermentation. Soy oil with about 20% CLA was obtained in a laboratory-scale study by simple photoisomerization of soy oil linoleic acid to CLA using an iodine sensitizer at 20 ◦ C, with little lipid oxidation. The system consisted of a jacketed reac- tion vessel with a UV lamp at the center. However, the photoirra- diation study took 144 h to produce 20% CLA. While this level of CLA is considerably greater than in current CLA food sources, the irradiation time should be much shorter to be of practical value. Jain and Proctor (2006) also showed that the concentration of iodine in soy oil significantly affects CLA production, probably by limiting oil UV light penetration. Jain and Proctor (2007a) suggested that mode of operation and temperature of photoprocessing may affect the CLA production rates and should be optimized. There is a need to produce CLA-rich oil more quickly and in larger quantities for the process to be industrially relevant. The goals of this study are to develop a pilot-scale means of rapidly producing greater quantities of high-CLA soy oil by photoir- radiation and to discover how various processing parameters affect CLA production. This will require some processing innovation to C  2008 Institute of Food Technologists Vol. 73, Nr. 4, 2008—JOURNAL OF FOOD SCIENCE E183 doi: 10.1111/j.1750-3841.2008.00718.x Further reproduction without permission is prohibited