14E-40 |
Thermal processing of vegetables increases cis isomers of lutein and zeaxanthin |
A. A. UPDIKE, Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007 and S. J. Schwartz. Carotenoids lutein and zeaxanthin, found in fruits and vegetables, comprise the macula pigment of the eye. Supplementation of these carotenoids has been found to be inversely associated with eye disease. In nature, these carotenoids exist in the all-trans geometric form however in human plasma cis isomers of these carotenoids have also been identified. Cis isomers in plasma could result from an in vivo isomerization of the all-trans isomer or the consumption of both the cis and all-trans forms. Thermal processing of fruits and vegetables can induce carotenoid trans to cis isomerization and also enhance the bioavailability due to breakdown of the plant tissue matrix. The aim of this research was to determine if thermal processing induces isomerization of lutein and zeaxanthin and to quantify the extent of this reaction. Broccoli, corn, peas, kale and spinach were subjected to thermal processing (retorting) according to the National Canners Association time and temperature requirements. High-performance liquid chromatography (HPLC) was used to separate and quantitate geometric isomers of lutein and zeaxanthin in fresh and processed vegetables. The isomers were resolved isocratically using a C30 stationary phase with 85:15 (methanol containing 2% of 1 M acetic acid: methyl-tert-butyl-ether) as mobile phase. The percent cis isomers of lutein and zeaxanthin increased up to 22% and 17%, respectively, with processing. Processing produced an increase of 4 to 42% of the total lutein content resulting from enhanced extraction efficiency and recovery from heat treated tissues. The presence of cis lutein and zeaxanthin in thermally processed vegetables may explain the detection of these compounds in human plasma. Although it is well known that these carotenoids and their stereoisomeric forms have a role in maintaining eye health, the physiological significance of consuming the geometrical cis isomers has yet to be explored.
Session 14E, Nutraceuticals & Functional Foods: General I
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