Processing effects on lycopene content and antioxidant activity of tomatoes

Consumption of tomato products has been associated with decreased risk of s ome cancer types, and the tomato antioxidant, lycopene, is thought to play an important role in the observed health effects. In this study, four carot enoids, trans-lycopene, phytofluene, phytoene, and xi -carotene, were quant ified in tomato products. Samples of raw tomatoes, tomato juice after hot b reak scalder, and final paste were obtained from two different processing p lants over two years. Comparison of carotenoid levels throughout processing indicated that lycopene losses during processing of tomatoes into final pa ste (25-30 degrees Brix) ranged from 9 to 28%. The initial Brix level of th e raw tomatoes appeared to influence the amount of lycopene loss that occur red, possibly due to the differences in processing time required to achieve the final desired Brix level of the paste. In general, no consistent chang es in the other carotenoids were observed as a function of processing. The antioxidant activity of fresh tomatoes, tomato paste, and three fractions o btained from these products (i.e., aqueous, methanol, and hexane fractions) was also determined. In both a free radical quenching assay and a singlet oxygen quenching assay, significant antioxidant activity was found in both the hexane fraction (containing lycopene) and the methanol fraction, which contained the phenolic antioxidants caffeic and chlorogenic acid. The resul ts suggest that in addition to lycopene, polyphenols in tomatoes may also b e important in conferring protective antioxidative effects.