Antioxidantes

Industrial Crops and Products 35 (2012) 126–134

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Industrial Crops and Products
journal homepage: www.elsevier.com/locate/indcrop

Response surface optimization of antioxidants extraction from chestnut (Castanea sativa) bur
G. Vázquez, A. Fernández-Agulló, C. Gómez-Castro, M.S. Freire, G. Antorrena, J. González-Álvarez ∗
Department of ChemicalEngineering, School of Engineering, University of Santiago de Compostela, Rúa Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain

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The chestnut bur, a forest waste product from chestnut processing in the food industry, was studied as a potential source of natural antioxidants. Extractions were performed using aqueous solutions of methanol orethanol. Experiments were planned according to an incomplete 33 factorial design to study the influence of temperature (25–75 ◦ C), time (30–120 min) and solvent concentration (50–90%) on extraction yield and on extract properties: total phenols content, antioxidant activity (using the FRAP, DPPH and ABTS methods) and average molecular weights. All dependent variables were influenced by temperatureand solvent concentration whereas the influence of time was almost negligible. Using the response surface methodology the optimal extraction conditions were selected: the highest temperature assayed (75 ◦ C), the lowest solvent concentration (50%) and an extraction time of 75 min for the methanolic extractions and of 30 min for the ethanolic ones. Under those conditions the values predicted forextraction yield and total phenols content were 18.95% and 36.32 g GAE/100 g extract for the methanolic extract and 17.95% and 26.11 g GAE/100 g extract for the ethanolic ones. Methanolic extracts showed superior total phenols content and antioxidant properties and slightly higher extraction yields than ethanolic extracts; however, ethanol is recommended for food applications due to its GRAS(Generally Recognized as Safe) qualification. Gallic acid esters of glucose, ellagic acid and small proportions of quercetin-3- -dglucoside, phenolic compounds with demonstrated antioxidant properties, were identified in chestnut bur extracts by RP-HPLC-ESI-TOF. © 2011 Elsevier B.V. All rights reserved.

Article history: Received 30 December 2010 Received in revised form 14 February 2011 Accepted 17 June2011 Available online 14 July 2011 Keywords: Chestnut bur Phenolic compounds Antioxidants Experimental design Response surface methodology RP-HPLC-ESI-TOF

1. Introduction The chestnut (Castanea sativa) is a traditional crop in Galicia (NW of Spain) where around 15,000 t/year of chestnut fruit are produced. Roughly half the production is destined for fresh consumption and the other half istransformed to obtain several derivates such as frozen fruit, chestnut purée or flour, chestnut in syrup or marron-glacé. Chestnut processing generates two waste products: the bur and the shell. The shell is separated in the peeling process and is used as fuel in the food factory whereas the bur usually remains in the woodland after the fruit harvesting and promotes the proliferation of certain insectlarvae which cause damages to crops. The valorisation of both residues would improve the industrial process both economically and environmentally. Based on their phenolic composition (Vasconcelos et al., 2010), this type of lignocellulosic wastes could be used as sources of natural antioxidants, since the beneficial effects derived from phenolic compounds, such as their anticarcinogenic,antimutagenic and cardioprotective activities, have been attributed to their antiox-

∗ Corresponding author. Tel.: +34 881816758; fax: +34 981528050. E-mail address: julia.gonzalez@usc.es (J. González-Álvarez). 0926-6690/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2011.06.022

idant activity (Madhavi et al., 1996; Balasundram et al., 2006). Thus, in the last few...