Chromatographic determination of the effect of storage on lycopene

A reverse-phase high-performance liquid chromatography (HPLC) method for the determination of lycopene in an alkaline lipid phase is described, and pigment stability in stored tomato sausage is reported. To avoid and replace the use of nitrite, lycopene from tomato products is added to minced meat and a tomato sausage with natural color is produced. Tomato sausage with and without nitrite were smoked in a smoking compartment and stored (4 degrees C and 8 degrees C) for 25 and 17 days, respectively. Among other factors, the quality of the tomato sausage depends on stability of lycopene during process and storage. Lycopene, being lipophilic, is extracted together with the polar and neutral fat in food. Efforts to purify lycopene from the fatty content will result in loss of pigment. The triacylglycerides obstruct the detection of lycopene by spectrophotometry or by HPLC with diode-array detection. To solve this problem, the triacylglycerides are hydrolyzed to free fatty acids just before analyzing lycopene on a column tolerating alkaline samples. At the end of the storage, loss of pigment in the sausage without nitrite was 26% stored at 4 degrees C and 19% at 8 degrees C. Corresponding results for the sausage with nitrite added as well as tomato paste show the loss of pigment is 20% and 45%. For each type of fatty food extracted, it is important to minimize the use of alkaline solutions because the HPLC equipment may be susceptible to alkaline conditions.