33G-20 |
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C. MORARU and T.-C. Lee. Dept. of Food Science, Rutgers, The State Univ. of New Jersey, Center for Advanced Food Technology, 65 Dudley Rd., New Brunswick, NJ 08901-8520 Lycopene isomerizes during processing, with formation of several cis (CL) isomers. Recent studies suggest that CLs may be more beneficial for human health than the naturally-predominant, all-trans isomer (ATL). Lycopene isomerization may be triggered both by thermal processing and by exposure to low pH, but the effect of gastric pH on the isomeric composition of lycopene is unclear. The objective of this study was to quantify the lycopene isomeric distribution following exposure to simulated gastric juice (SGJ, pH 1.5) at 37°C, and to compare it with our previous data on the isomeric distribution for lycopene subjected to thermal processing. ATL was extracted from tomatoes and further purified by column chromatography. CLs were isolated by preparative HPLC, using a heated (85°C/5min) ATL solution as source. The prevailing CL isomer was collected and used for the experiment. Emulsions were prepared from hexane solutions of lycopene isomers and SGJ, and they were incubated at 37°C for up to 6 hours. The concentration of lycopene isomers in the samples was afterwards quantified using analytical HPLC. When starting with both ATL and 13-CL solutions, the Q-ratios of the main CLs (tentatively identified as 13- and 9-CL) to ATL reached 0.3-0.5 after 4 hours. Data suggests that equilibrium between the isomeric forms, characterized by a total CLs:ATL ratio around 45:55, will eventually be reached. The isomeric distribution resulting from gastric pH exposure seems to favor formation of 9-CL, while 13-CL is the main isomer formed during thermal processing, as found previously. Assuming equal absorbtion coefficients for the lycopene isomers, the total CLs:ATL ratios found are very close to the ones reported in vivo. These findings suggest that isomerization in the stomach may be a major cause of the high level of CLs in the body.
Session 33G, Nutraceuticals & Functional Foods: Lipid and probiotic functional foods
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