14E-2 |
A comparison of the storage behavior of selected lycopene isomers in a food model system |
C. MORARU and T. C. Lee. Dept. of Food Science, Rutgers, The State Univ. of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901-8520 Lycopene isomerizes relatively easily during processing, with formation of many cis (CL) isomers. Recent studies suggest that CLs may be more valuable for human health than the naturally-predominant, all-trans isomer (ATL). Since ATL is the most thermodynamically-stable form, we hypothesized that it is also more stable than CLs during storage at various temperatures and were interested in quantifying the difference in stability. This subject is not documented, and may give new insights to understanding the lycopene isomerization process. Our objective was to compare the loss of both ATL and the major CLs during storage at various temperatures between 0 and 100oC. ATL was extracted from tomatoes and further purified by column chromatography. CLs were isolated by preparative HPLC, using a cooked ATL solution as source. The prevailing CL isomer was collected and used for the experiment. Tributyrin solutions of both isomers were subjected to temperatures between 0 and 100oC, for various durations. The isomeric composition of the samples after exposure was quantified using analytical HPLC. Our results showed that at high temperatures ATL is significantly more stable that CL. However, under refrigeration we found CL about 20% more stable than ATL, suggesting that at lower temperatures the thermodynamic stability may be less important. In all cases we found that some of the loss is due to re-isomerization, which indicates that the isomerization process is reversible. The ratio between the two isomers seems to converge to the same value for all samples and conditions tested. These results are useful in understanding the kinetics of lycopene loss and isomerization during processing and storage. Predictive models for the behavior of ATL and CL during heating and storage in real food systems, with practical utility for industry, could be developed based on the data above.
Session 14E, Nutraceuticals & Functional Foods: General I
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