Talanta 88 (2012) 544–552 Contents lists available at SciVerse ScienceDirect Talanta jo u r n al hom epage: www.elsevier.com/locate/talanta Supercritical fluid extraction from spent coffee grounds and coffee husks: Antioxidant activity and effect of operational variables on extract composition Kátia S. Andrade a , Ricardo T. Gonc ¸ alvez a , Marcelo Maraschin b , Rosa Maria Ribeiro-do-Valle c , Julian Martínez d , Sandra R.S. Ferreira a,∗ a Chemical and Food Engineering Department, Federal University of Santa Catarina, EQA/UFSC–C.P. 476, CEP 88040-900, Florianópolis, SC, Brazil b Department of Phytotechny, Federal University of Santa Catarina, CEP 88034-001, Florianópolis, SC, Brazil c Department of Pharmacology, Federal University of Santa Catarina, CEP 88049-900, Florianópolis, SC, Brazil d School of Food Engineering, University of Campinas, FEA/UNICAMP, CEP 13083-862, Campinas, SP, Brazil a r t i c l e i n f o Article history: Received 8 July 2011 Received in revised form 10 November 2011 Accepted 10 November 2011 Available online 17 November 2011 Keywords: Supercritical method Coffee residues Composition Antioxidant activity a b s t r a c t The present study describes the chemical composition and the antioxidant activity of spent coffee grounds and coffee husks extracts, obtained by supercritical fluid extraction (SFE) with CO 2 and with CO 2 and co- solvent. In order to evaluate the high pressure method in terms of process yield, extract composition and antioxidant activity, low pressure methods, such as ultrasound (UE) and soxhlet (SOX) with different organic solvents, were also applied to obtain the extracts. The conditions for the SFE were: temperatures of 313.15 K, 323.15 K and 333.15 K and pressures from 100 bar to 300 bar. The SFE kinetics and the math- ematical modeling of the overall extraction curves (OEC) were also investigated. The extracts obtained by LPE (low pressure extraction) with ethanol showed the best results for the global extraction yield (X 0 ) when compared to SFE results. The best extraction yield was 15 ± 2% for spent coffee grounds with ethanol and 3.1 ± 04% for coffee husks. The antioxidant potential was evaluated by DPPH method, ABTS method and Folin–Ciocalteau method. The best antioxidant activity was showed by coffee husk extracts obtained by LPE. The quantification and the identification of the extracts were accomplished using HPLC analysis. The main compounds identified were caffeine and chlorogenic acid for the supercritical extracts from coffee husks. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Brazil is currently the world’s largest producer of coffee, repre- senting near 30% of the global market, with a volume equivalent to the sum of production of the other six countries with the high- est production [1]. The quality of coffee, in addition to the sensory attributes can be accessed through the identification and quantifi- cation of the components present in this product, such as caffeine, which is associated to human health, trigonelline and chlorogenic acids, which are compounds responsible for the formation of flavor during roasting [2]. The large production and consumption of coffee also leads to the generation of a huge amount of waste. According Badocha et al. [3], the amount of coffee husks generated during processing is equiv- alent to the total amount of beneficiated grains. In a soluble coffee industry, for every ton of coffee produced, 4.5 tons of coffee grounds are generated, with approximately 80% moisture. Despite the large amount of waste generated by the agricultural and agribusiness, ∗ Corresponding author. Tel.: +55 48 37219448; fax: +55 48 37219687. E-mail address: sandra@enq.ufsc.br (S.R.S. Ferreira). only a small percentage is utilized because of the lack of knowledge related to its energy potential and also to the lack of appropriate equipment for their use [4]. The coffee husk is the main residue from the processing of coffee and is normally used in ruminant feed. However, it is considered anti-nutritional due to the pres- ence of toxic substances for these animals, such as caffeine (1.2%), tannins (6.3%) and polyphenols [5]. Because of the importance of the different compounds present in the coffee waste, the extraction of these substances appears as an important alternative to increase the aggregated value of the agro- industrial residues. The quality of extracts obtained from a raw material is strongly related to the extraction technique employed, and the quality of the extracts is measured by the chemical profile of the product. Supercritical technology is then a modern tech- nique for extraction that seeks to increase quality by exploiting the selectivity of the process, one of its main characteristics [6,7]. Therefore, this study proposes to obtain extracts from coffee husks and from coffee grounds (Coffea arabica) in order to evaluate the application of supercritical technology in obtaining compounds of high added value by analyzing the composition profile and the biological activity of the extracts. The determination of the kinetic parameters of the process was also object of investigation. 0039-9140/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2011.11.031