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Abstract(s)
Tomato (Lycopersicon esculentum Mill.) is the second most important vegetable crop worldwide and a
rich source of hydrophilic (H) and lipophilic (L) antioxidants. The H fraction is constituted mainly by
ascorbic acid and soluble phenolic compounds, while the L fraction contains carotenoids (mostly
lycopene), tocopherols, sterols and lipophilic phenolics [1,2]. To obtain these antioxidants it is necessary
to follow appropriate extraction methods and processing conditions. In this regard, this study aimed at
determining the optimal extraction conditions for H and L antioxidants from a tomato surplus. A 5-level
full factorial design with 4 factors (extraction time (I, 0-20 min), temperature (T, 60-180 •c), ethanol
percentage (Et, 0-100%) and solid/liquid ratio (S/L, 5-45 g!L)) was implemented and the response surface
methodology used for analysis. Extractions were carried out in a Biotage Initiator Microwave apparatus.
The concentration-time response methods of crocin and P-carotene bleaching were applied (using 96-well
microplates), since they are suitable in vitro assays to evaluate the antioxidant activity of H and L
matrices, respectively [3]. Measurements were carried out at intervals of 3, 5 and 10 min (initiation,
propagation and asymptotic phases), during a time frame of 200 min. The parameters Pm (maximum
protected substrate) and V m (amount of protected substrate per g of extract) and the so called IC50 were
used to quantify the response. The optimum extraction conditions were as follows: r~2.25 min, 7'=149.2
•c, Et=99.1 %and SIL=l5.0 giL for H antioxidants; and t=l5.4 min, 7'=60.0 •c, Et=33.0% and S/L~l5.0
g/L for L antioxidants. The proposed model was validated based on the high values of the adjusted
coefficient of determination (R2.wi>0.91) and on the non-siguificant differences between predicted and
experimental values. It was also found that the antioxidant capacity of the H fraction was much higher
than the L one.
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Citation
Pinela, José; Prieto, M.A.; Barreiro, M.F.; Carvalho, Ana Maria; Oliveira, M.B.P.P.; Vásquez, J.A.; Ferreira, Isabel C.F.R. (2016). Crocin and β-Carotene bleaching assays as analytical tools in the optimization of the extraction of hydrophilic and lipophilic antioxidants from tomato. In 5° Encontro Português de Jovens Químicos (PYCheM) e o 1° Encontro Europeu de Jovens Químicos (EYCHeM). Guimarães