Impact of blanching, freezing and frozen storage on the carotenoid profile of carrot slices (Daucus carota L. cv. Nutri Red)

The Nutri Red carrot (Daucus carota L. cv. Nutri Red), a red carrot variety which together with β-carotene contains large amounts of lycopene, could represent an interesting alternative to tomatoes as a source of lycopene in the European diet. However, carotenoid retention during processing of this carrot variety has not yet been sufficiently addressed. The interest here is focused on the evaluation of the potential carotenoid degradation and/or isomerisation resulting from blanching, freezing and during the subsequent frozen storage of Nutri Red carrots. Carrots were sliced, blanched, air blast frozen and stored at −50 °C, −30 °C, −18 °C and −15 °C for up to two years. β-carotene, α-carotene, and lutein remained stable along processing and long-term frozen storage. All-trans-lycopene was degraded at all storage temperatures. A first-order and a two-first-order reaction models were applied for the description of lycopene degradation. The temperature dependence of the rate constants was adequately modelled by the Arrhenius equation at temperatures above −30 °C. Although substantial losses of all-trans-lycopene were detected, the carrot slices still exhibited lycopene contents similar to that of some tomato varieties after one year storage at −18 °C. Hence, both raw and frozen Nutri Red carrots represent an excellent alternative lycopene source.