Recovery and Isomerization of Carotenoids from Tomato Processing By-products

Industrial tomato processing by-products are intended mainly for animal feed or fertilizer, though they can be used for the recovery of valuable constituents. Carotenoids constitute an important component of these by-products, well credited with important health-promoting functions. This study examined the effect of several organic solvents (hexane, ethanol, acetone, ethyl acetate, ethyl lactate and their mixtures), and extraction temperature on the recovery and isomerization of carotenoids from tomato processing by-products. Another area under investigation was the stability of carotenoids, as affected by drying and storage conditions of tomato by-products. HPLC-DAD analysis was applied for the efficient separation and analysis of the carotenoids and their cis-isomers. The highest extraction yield was obtained with ethyl lactate (203.6 mu g/g dry by-product) followed by hexane-ethyl acetate mixture with a considerably lower yield (36.1 mu g/g dry by-product). The identified carotenoids in all solvent extracts followed the order: lycopene >> beta-carotene > lutein, in their predominant trans-configuration. Among the identified isomers, 5-cis lycopene and 15-cis-beta-carotene were the most abundant in all extracts. The increase of extraction temperature increased the total lycopene concentration in all extracts, whereas cis-isomers remained lower than 8 % in most solvents. A steadily high percentage of cis-isomer (approximate to 30 %) was observed in ethyl lactate extracts, independent of temperature. Conversely, the increase of extraction temperature induced a reduction in total beta-carotene and total lutein concentration in all solvents, while cis-isomers were not detected. Drying or even cold storage of the raw material led to decreased yields, and affected lycopene isomerization with a considerable increase of cis-isomers.