Abstract
Tomatoes and tomato products are rich sources of carotenoids—principally lycopene, followed by β-carotene and lutein. The aim of this work was to study the effect of heat treatment on carotenoid content in cherry tomatoes. Raw and canned products were sampled and analysed; furthermore whole, skin and pulp fractions of cherry tomatoes were analysed when raw and home-processed, in order to better understand heat treatment effects. Lycopene content in canned tomatoes was two-fold higher than in raw tomatoes (11.60 mg/100 g versus 5.12 mg/100 g). Lutein and β-carotene were respectively 0.15 mg/100 g and 0.75 mg/100 g in canned tomatoes versus 0.11 mg/100 g and 1.00 mg/100 g in raw tomatoes. For home-processed tomatoes, β-carotene and lutein showed a content decrease in all thermally treated products. This decrease was more evident for β-carotene in the skin fraction (−17%), while for lutein it was greater in the pulp fraction (−25%). Lycopene presented a different pattern: after heat treatment its concentration increased both in the whole and in pulp fractions, while in the skin fraction it decreased dramatically (−36%). The analysis of the isomers formed during the thermal treatment suggests that lycopene is rather stable inside the tomato matrix.
Highlights
Carotenoids are pigments ubiquitous in nature and responsible for the bright yellow to dark red colour of vegetal products
Studies on bioavailability provides evidence that industrial tomato products are a better source of carotenoids than raw ones [17,18,19,20]: in particular lycopene extractability significantly increases after thermal pasteurization and mechanic homogenization treatments due to the breaking of protein complexes where the pigment is associated inside the vegetable matrix [21,22,23,24]
Results from a study by Abushita et al [13] on the effects of technological treatments on tomato carotenoids were found to be consistent with those in the present research: analysis performed in raw and thermally and mechanically treated salad tomatoes demonstrated that lycopene extractability increased after heating (+37%), while β-carotene and lutein were partially degraded by heat (−29% and −3%, respectively)
Summary
Carotenoids are pigments ubiquitous in nature and responsible for the bright yellow to dark red colour of vegetal products. A number of epidemiological studies have shown that a large consumption of lycopene-rich food is inversely correlated with the risk of developing prostate cancer, while intake of fruit and vegetables is not related with these types of tumours [14,15,16]. Studies on bioavailability provides evidence that industrial tomato products are a better source of carotenoids than raw ones [17,18,19,20]: in particular lycopene extractability significantly increases after thermal pasteurization and mechanic homogenization treatments due to the breaking of protein complexes where the pigment is associated inside the vegetable matrix [21,22,23,24]
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