Numerous studies have reported on the carotenoid content of various vegetables in their natural raw state(1). 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.)(2). The carotenoid content of the samples was quantified by HPLC(3).
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):
The lycopene and β-carotene content of the raw tomatoes tested is in agreement with values reported in the literature(1). 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).