Numerous studies have reported on the carotenoid content of various vegetables in their natural raw state(Reference Maiani, Periago Caston and Catasta1). However, many foods are subjected to various processing procedures before consumption. Tomatoes are a commonly-consumed fruit vegetable that are available in many different forms such as raw and canned, as well as tomato-based sauces and juices. Thus, the objective of the present study was to compare the carotenoid content of tomato-based sauces and juices with that of raw tomatoes. The carotenoids analysed were lycopene and β-carotene, which are the predominant carotenoids present in tomatoes.
The food products were purchased from a local supermarket chain. All work was performed under amber light to minimise photodecomposition of the carotenoids. Each food was weighed (approximately 2 g) and homogenised. The samples were then extracted twice using a solvent mixture of hexane–acetone–ethanol (2:1:1, by vol.)(Reference Olives, Hurtado and Mata2). The carotenoid content of the samples was quantified by HPLC(Reference Hart and Scott3).
Values are means for four independent experiments. Mean values were significantly different from those for raw tomatoes (one-way ANOVA, followed by Dunnett's test):
* P<0.05.
The lycopene and β-carotene content of the raw tomatoes tested is in agreement with values reported in the literature(Reference Maiani, Periago Caston and Catasta1). Canned tomatoes, ketchup, and relish had significantly greater amounts (P<0.05) of lycopene compared with the raw tomatoes. The mixed vegetable juice had lower levels of lycopene compared with the raw tomatoes; however, it is important to bear in mind that the mixed vegetable juice was produced using several vegetables and not just tomato. In relation to β-carotene content, only the Bolognese sauce and mixed vegetable juice contained significantly greater amounts (P<0.05) compared with the raw tomatoes. This result may be explained by the presence of carrots in these food products. In conclusion, processing did not have a significant effect on β-carotene content whereas lycopene content was enhanced in the tomato-based processed food products.
This work was supported by Science Foundation Ireland (PI Award 04/IN3/B509).
