Effect of high hydrostatic pressure on lycopene stability

The stability and isomerization of lycopene by high hydrostatic pressure (HHP) were evaluated. Lycopene standard in hexane and tomato puree were pressurized at 100, 200, 300, 400, 500 and 600 MPa for 12 min at controlled temperature (20 ± 1 °C). After application of pressure, samples were stored at refrigerator temperature (4 ± 1 °C) and ambient laboratory temperature (24 ± 1 °C) under lightproof conditions. HPLC and spectral analysis were employed to analyze lycopene and its cis-isomers in samples after HHP and after 2, 4, 8 and 16 days of storage. High pressure affected the content of total lycopene and the percentage of the presumptive 13-cis isomer, both in lycopene solution and tomato puree. Furthermore, the higher the storage temperature, the greater was the loss of total lycopene and the higher the percentage of 13-cis isomer. However, the pressure effects were widely different in lycopene solution and tomato puree. 500 and 600 MPa led to a significant (P < 0.05) loss of lycopene while 400 MPa retained the maximal stability of lycopene in solution. The highest stability of lycopene was found when tomato puree was pressurized at 500 MPa and stored at 4 ± 1 °C.