Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/8/2001
Publication Date: 7/17/2001
Citation: Takeoka, G.R., Dao, L.T., Flessa, S., Gillespie, D.M., Jewell, W.T., Huebner, B.H., Bertow, D., Ebeler, S.E. 2001. Processing effects on lycopene content and antioxidant activity of tomatoes. Journal of Agricultural and Food Chemistry. Vol 49:3713-3717. Interpretive Summary: Recent epidemiological evidence suggests that the carotenoid lycopene may reduce the risk of developing cervical, colon, prostate, rectal and stomach cancers. The main dietary source of lycopene, a red-colored carotenoid, is tomatoes and tomato products. Due to its importance, it is critical to understand the role of lycopene in the diet and its stability during processing. In this study, we systematically monitored lycopene concentration in fresh tomatoes as they were processed into paste. Our results showed that lycopene losses during processing of tomatoes into final paste ranged from 9-28%. The initial Brix level of the raw tomatoes appeared to influence the amount of lycopene loss that occurred, possibly due to the differences in processing time required to achieve the final desired Brix level of the paste. Development of processing tomatoes with higher levels of soluble solids is thought to be advantageous since they could result in higher levels of lycopene in processed tomato products such as paste.
Technical Abstract: Four carotenoids, trans-lycopene, phytofluene, phytoene, and zeta-carotene were quantified in tomato products. Samples of raw tomatoes, tomato juice after hot break scalder, and final paste were obtained from two different processing plants over two years. Comparison of carotenoid levels throughout processing indicated that lycopene losses during processing of tomatoes into final paste (25 to 30 degrees Brix) ranged from 9 to 28%. The initial Brix level of the raw tomatoes appeared to influence the amount of lycopene loss that occurred, possibly due to the differences in processing time required to achieve the final desired Brix level of the paste. Antioxidant activity of fresh tomatoes, tomato paste, and three fractions obtained from these products (i.e., aqueous, methanol and hexane fractions) was also determined. In both a free radical quenching assay and singlet oxygen quenching assay, significant antioxidant activity was found in both the hexane fraction (containing lycopene) and in the methanol fraction which contained the phenolic antioxidants, caffeic and chlorogenic acid. The results suggest that in addition to lycopene, polyphenols in tomatoes may also be important in conferring protective antioxidative effects.