Effect of Ultra-High Pressure Technology on Isomerization and Antioxidant Activity of Lycopene in Solanum Lycopersicum

To evaluate the influence of the Ultra-High Pressure processing (UHP) on the isomerization and antioxidant activity of lycopene in tomatoes (Solanum lycopersicum), High Performance Liquid Chromatography (HPLC) and Ultraviolet-Visible Spectroscopy (UV-Vis) were used to separate and identify the isomer of lycopene. The scavenging activities against DPPH∙and∙OH present samples with and without UHP treatment were tested with ascorbic acid as positive control. Full wavelength scanning figure showed that a characteristic absorption peak was created at 361 nm, which was caused by trans-lycopene isomerizing into cis isomer. HPLC analysis found that five peaks (Rt = 19.082, 13.307, 9.790, 8.123, 7.207 min) were produced after UHP treatment, which were further identified by UV-Vis and four peaks among them showed a strong absorption peak at 361 nm which was in accordance with the UV-Vis spectroscopy of cis-lycopene. The total antioxidant, capable of scavenging hydroxyl radicals·OH and DPPH·radical of lycopene treated by UHP, were all higher than that of control and lycopene without UHP treated. Taken together, UHP treatment played the role in cis-trans conversion of lycopene and could also improve the antioxidant activity of lycopene oleoresin with a dose-dependent fashion.