Optimization of microwave-assisted extraction of hydrophilic and lipophilic antioxidants from a surplus tomato crop by response surface methodology
2016
Pinela, José | Prieto, M.A. | Barreiro, Maria Filomena | Carvalho, Ana Maria | Oliveira, M. Beatriz P.P. | Vázquez, J.A. | Ferreira, Isabel C.F.R.
Tomato is the second most important vegetable crop worldwide and a rich source of industrially interesting antioxidants. Hence, the microwave-assisted extraction of hydrophilic (H) and lipophilic (L) antioxidants from a surplus tomato crop was optimized using response surface methodology. The relevant independent variables were temperature (T), extraction time (t), ethanol concentration (Et) and solid/liquid ratio (S/L). The concentration-time response methods of crocin and β-carotene bleaching were applied, since they are suitable in vitro assays to evaluate the antioxidant activity of H and L matrices, respectively. The optimum operating conditions that maximized the extraction were as follows: t, 2.25min;T, 149.2°C; Et, 99.1%; and S/L, 45.0g/L for H antioxidants; and t, 15.4min;T, 60.0°C; Et, 33.0%; and S/L, 15.0g/L for L antioxidants. This industrial approach indicated that surplus tomatoes possess a high content of antioxidants, offering an alternative source for obtaining natural value-added compounds. Additionally, by testing the relationship between the polarity of the extraction solvent and the antioxidant activity of the extracts in H and L media (polarity–activity relationship), useful information for the study of complex natural extracts containing components with variable degrees of polarity was obtained.
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