Process optimization for recovery of carotenoids from tomato waste
Irini F.Strati, Vassiliki Oreopoulou
Laboratory of Food Chemistry and Technology, School of Chemical Engineering, National Technical
University of Athens, Iroon Polytechniou 5, 15780 Zografou, Athens,Greece([email protected])
INTRODUCTION
Carotenoids, well credited with important health-promoting functions or actions [1], constitute
an important component of waste originating from tomato processing plants. Most extraction
methods of carotenoids use organic solvents or solvent mixtures as well as supercritical fluids.
Comparison of efficiency among different solvents for carotenoid extraction from various plant
materials is presented in literature [2], but few of them concern tomato waste and, moreover,
deal with the optimization of extraction conditions [3]. The aim of the present work was to
assess the extraction yield of tomato waste carotenoids in different solvents and solvent
mixtures and to optimise the extraction conditions as regards the synthesis of the solvent
mixture, the ratio of solvent mixture to waste, and the particle size of the dried ground waste,
using response surface methodology.
MATERIALS & METHODS
Carotenoids were extracted using different polar (acetone, ethyl acetate and ethanol) and non
polar (hexane) solvents [4] and solvent mixtures. The first series of experiments was conducted
with single solvents or mixtures of equal volumes (50:50) at a solvent to waste ratio of 10:1
(v/w), while the particle size of the dry tomato waste was 1.0 mm. The second series of
factorial designed experiments were conducted with mixtures of hexane and ethyl acetate
varying among 10:90 and 80:20 (v/v), solvent to waste ratio varying among 3:1 and 10:1 (v/w),
and particle size among 0.5 and 1.0 mm. The carotenoid content of the supernatant was
measured spectrophotometrically at λmax for lycopene in each solvent or solvent mixture. For
the identification of individual carotenoids, the extracts obtained by single solvents or solvent
mixtures were further analysed by high performance liquid chromatography (HPLC).
RESULTS & DISCUSSION
The results presented in Table 1 concern the total carotenoid yield of the three successive
extraction steps and the percentage of individual carotenoids identified by HPLC analysis. The
combination of hexane with ethanol or ethyl acetate improved the total yield compared with
that obtained by any of the individual solvents. The highest carotenoid yield (36.5 mg kg-1) was
obtained when carotenoids were extracted with a mixture of ethyl acetate and hexane. The
combination of polar solvents with the non polar hexane seemed to enhance the solubilisation
of the non polar carotenoids (lycopene and β-carotene), whereas individual polar solvents
(ethanol, acetone and ethyl acetate) enhanced the solubilisation of the polar lutein.
Table 1. Total carotenoid yield and percentage of HPLC separated carotenoids from tomato waste
extracted with different solvents and solvent mixtures, at 25 °C, solvent:waste ratio of 10 v/w, and waste
particle size of 1 mm.
βLutein
Solvent/Solvent
Carotenoid Yield (mg kg-1 dry Lycopene
waste)
carotene
mixture
Ethanol
6.1 ± 0.3a
70±3%
10±1%
20±1%
nd
Hexane
25.2 ± 0.7b
97±2%
2±0.5%
Ethyl acetate
31.5 ± 0.2d
82±4%
13±1%
5±0.5%
Acetone
33.4 ± 0.3e
84±3%
8±0.5%
8±0.5%
Hexane-Ethanol
28.1 ± 0.6c
84±4%
14±2%
<3%
(50:50)
Hexane-Acetone
30.5 ± 0.8d
85±3%
12±1%
<3%
(50:50)
Hexane-Ethyl
36.5 ± 1.1f
95±3%
2±0.5%
3±0.5%
acetate (50:50)
In order to determine the combined effect of different levels of hexane percentage in the
hexane-ethyl acetate solvent mixture (X1), solvent to waste ratios (X2) and different particle
sizes (X3) on carotenoid yield (Y), optimization experiments were conducted. A polynomial
model describing the correlation between carotenoid yield (Y) and the three processing
variables (X1,X2,X3) was derived and the established model was found to be significant
(P<0.05) and useful to predict the carotenoid yield at different levels of three examined factors,
influencing the extraction. The desirability profile for optimum carotenoid yield indicated that
the maximum desirability of 1.0 (in a scale of 0-1) can be achieved with 45% hexane in the
solvent mixture, at a solvent to waste ratio (v/w) 9:1 and particle size 0.575 mm.
CONCLUSION
The use of a mixture of polar and non-polar solvents, namely ethyl acetate and hexane, proved
adequate to extract non polar carotenoids (lycopene and β-carotene) in sufficient percentages
(96% of total extracted carotenoids), as well as the polar lutein (4% of total extracted
carotenoids). The optimized conditions, according to the experimental design, comprising
fifteen selected combinations of percentage of hexane in the solvent mixture, solvent to waste
ratio and particle size, were found to be 45% hexane in the solvent mixture of ethyl acetate and
hexane, a solvent to waste ratio of 9.1:1 (v/w) and particle size 0.56 mm, and the respective
yield amounted to 37.5 mg kg-1 dry waste..
REFERENCES
[1] Fraser P. & Bramley P. 2004. The biosynthesis and nutritional uses of carotenoids. Progress in Lipid
Research, 43, 228–265.
[2] Lin C. H. & Chen B. H. 2003. Determination of carotenoids in tomato juice by liquid
chromatography. Journal of Chromatography, 1012, 103–109.
[3] Kaur D., Wani A. A., Oberoi D. P. S. & Sogi D. S. 2008. Effect of extraction conditions on lycopene
extractions from tomato processing waste skin using response surface methodology. Food
Chemistry, 108(2), 711-718.
[4] Strati I. F. & Oreopoulou V. 2011. Effect of extraction parameters on the carotenoid recovery from
tomato waste. International Journal of Food Science and Technology, 46, 23-29.