Extraction of Caffeine from Natural Matter Using a Bio-Renewable Agrochemical Solvent

food and bioproducts processing 9 1 ( 2 0 1 3 ) 303–309 Contents lists available at ScienceDirect Food and Bioproducts Processing j ournal homepage: www.elsevier.com/locate/fbp Extraction of caffeine from natural matter using a bio-renewable agrochemical solvent a a b b David Villanueva Bermejo , Pilar Luna , Marina S. Manic , Vesna Najdanovic-Visak , a a,∗ Guillermo Reglero , Tiziana Fornari a Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM+CSIC, C/Nicolás Cabrera 9, Campus de Cantoblanco, 28049 Madrid, Spain b REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal a b s t r a c t This paper reports experimental data on the pressurized liquid extraction of caffeine from green coffee beans and green tea leaves using ethyl lactate (ethyl 2-hydroxy-propanoate). This solvent is a new bio-renewable agrochemical solvent, naturally produced by fermentation from corn derived feedstock, which has been recently considered as a very suitable and environmental benign solvent for food industrial applications. Static extraction assays (one step during 10 min) were carried out in an Accelerated solvent extraction (ASE) system ◦ at three different extraction temperatures, namely 100, 150 and 200 C. Extraction yield and caffeine recovery were determined and compared with those obtained when using other liquid solvents, such as ethyl acetate or ethanol. High recovery of caffeine (≈60%) was found in the extracts produced using ethyl lactate, which demonstrates the potential use of this green solvent for the extraction of caffeine from different vegetable sources. © 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Coffee; Green tea; Caffeine; Ethyl lactate; Accelerated solvent extraction 1. Introduction acids (elagic, caffeic and chlorogenic acids) to which several biological properties have been attributed (Naidu et al., 2008; Coffee plant belongs to the genus Coffea of the Rubiaceae fam- Brezova et al., 2009). ily with more than 70 species, but only two of them have Another plant that contains caffeine is green tea (Camel- economic and commercial importance: the species Arabica lia sinensis), which has been a much consumed drink in (Coffea arabica) and Robusta (Coffea robusta) (Alonso-Salces Asian countries over years. Nowadays, it is very popular et al., 2009). Arabica coffee beans are preferred by consumers all over the world, due to its recognized beneficial health and are considered of superior quality at the international effects. Green tea leaves contains caffeine, catechins, fats, market (Meinhart et al., 2010). amino acids, aroma chemical, vitamins and chlorophyll, Coffee is one of the most traded commodities, and is one of among others (Stone et al., 1991). Indeed, the major bioac- the most popular drinks in the world due to its unique flavor tive components are caffeine and catechins. Caffeine content and sensory characteristics. Coffee beans are an important is around 20–40 mg/g while catechins are in the range of source of caffeine, which is the most common consumed 190–260 mg/g (Park et al., 2007a,b; Perva-Uzunalic et al., alkaloid in the world. Depending on coffee variety, caffeine 2006). Catechins are recognized to be the beneficial bioactive content in green beans is around 1–2 %mass (Ashihara and compounds of green tea, including antioxidant, anticancer, Crozier, 2001). Other active principles present in coffee beans anti-inflammatory, antibiotic and antiviral effects (Cai et al., are coffee oil, an ingredient of special interest for the cosmetic 2002; Tedeschi et al., 2002; Cooper et al., 2005). Thus, the and pharmaceutical industries (Folstar, 1985), and phenolic consumption of green tea is considerably increasing, so as products with green tea flavor such as beverages and ice- creams. ∗ Corresponding author. Tel.: +34 910017972; fax: +34 910017905. E-mail address: [email protected] (T. Fornari). Received 20 August 2012; Received in revised form 26 October 2012; Accepted 14 November 2012 0960-3085/$ – see front matter © 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fbp.2012.11.007 304 food and bioproducts processing 9 1 ( 2 0 1 3 ) 303–309 Unquestionably, supercritical CO2 (SCCO2) extraction has green coffee beans and green tea leaves using ethyl lactate is proved to be the most convenient commercial and environ- presented for the first time. mental friendly technology for the removal of caffeine from green coffee beans (Zosel, 1978). SCCO2 is selective for the caf- 2. Materials and methods feine, there is no associated waste treatment of a toxic solvent and extraction times are generally moderate. SCCO2 coupled 2.1. Samples and reagents with a cosolvent, such as ethanol or water, was employed to extract caffeine form green tea leaves. By varying the extrac- Green coffee beans (C. arabica variety) and green tea (C. sinen- tion conditions, it is expected to maximize the amount of sis) leaves were acquired in a Spanish market. Water content caffeine extracted and minimize the co-extraction of bioac- in beans and leaves was determined to be, respectively, 11.2% tive catechins. Nevertheless, substantial losses of catechins and 6.2%. The moisture content was determined by oven dry- proved to be unavoidable (Kim et al., 2008; Park et al., 2007a,b). ◦ ing at 80 C until a constant weight was obtained. Among liquid solvents traditionally employed for cof- The coffee beans were ground in a ceramic mortar using fee decaffeination, benzene, chloroform, trichloroethylene liquid nitrogen; particle sizes were separated by using sieves and dichloromethane have been used over years. However, with manual agitation. Tw o different sizes of particles were when evidence suggested that chlorinated solvents might employed in the experiments: the entire green beans and be carcinogenic (Lynge et al., 1997) their use was severely ground beans with particles in the range of 500–1500 ␮m. The reduced. green tea leaves were ground in a manual knife mill using Extraction with water (definitely a green solvent) is also liquid nitrogen; particle of sizes 200–500 ␮m were employed called “indirect extraction” since a two-step process is for the experiments and were separated by using sieves with required: coffee beans are first soaked in water, an organic manual agitation. solvent is employed to selectively extract caffeine from water, Ethyl lactate (≥98% purity) and ethyl acetate (≥99.7% and the caffeine-free water goes back in contact with the purity) were obtained from Sigma–Aldrich (St. Louis, MO, beans and is evaporated (Clarke, 2003). This procedure strips USA), and ethanol (99.5% (v/v) purity) from Panreac (Castel- away many of the essential flavor and aroma substances. Ethyl lar del Vallés, Barcelona, Spain). Caffeine standard (≥99.0% acetate is much more selective for caffeine and thus, extrac- purity) was obtained from Fluka (Höchstädtan der Donau, tion can be accomplished in a single-step contact process Germany). (“direct extraction”). Since ethyl acetate presents much less health and environmental hazard than chlorinated solvents, decaffeination of coffee beans using this solvent is often called 2.2. Accelerated solvent extraction (ASE) “natural decaffeination” despite the fact that the ethyl acetate employed was obtained from synthesis and not from natural Caffeine extraction was carried out in an Accelerated Solvent sources. Extraction System ASE 350 from Dionex Corporation (Sun- As green coffee beans, the current commercially avail- nyvale, CA, USA) equipped with a solvent controller unit. A able methods for decaffeinating green tea leaves have been scheme of the equipment is shown in Fig. 1. solvent based extraction, using chlorinated solvents, ethyl In the case of coffee beans samples, extractions were per- acetate, acetone, methanol, ethanol and acetonitrile (Senol formed with three different liquid solvents (i.e. ethyl lactate, and Aydin, 2006). Effective decaffeination can be achieved ethanol and ethyl acetate) at three different extraction tem- ◦ using these solvents but catechins are also significantly co- peratures (100, 150 and 200 C) using 3 g of solid sample. The extracted, reducing the value of green tea as a functional extraction of caffeine from green tea leaves was performed at ◦ healthy drink. 100, 150 and 200 C, with ethyl lactate and ethanol as extrac- Ethyl lactate (ethyl 2-hydroxy-propanoate) is an agrochem- tive solvents. In this case, each cell was filled with around 1 g ical and economically viable alternative to traditional liquid of solid sample. solvents, and it is fully biodegradable, non-corrosive, non- Several preliminary assays were carried out in order to carcinogenic and non-ozone depleting. It was self-affirmed analyze the effect of time in the extraction procedure. At ◦ GRAS (generally recognized as safe) and due to its low tox- 200 C, very similar yields were obtained employing 10 min icity, was approved by the U.S. Food and Drug Administration and 20 min of static extraction, being the differences lower (FDA) as pharmaceutical and food additive. These characteris- than 15%. In view of this, and in order to reduce the possibil- tics have increased the attention to the use of ethyl lactate as ity of thermal degradation, a static extraction time of 10 min a green solvent for the food industry. Several reported poten- was selected to carry out all experiments. tial applications are related with the extraction of carotenoids The experimental procedure for both raw materials was as from different plant matrix (Ishida and Chapman, 2009; Strati follows. The cells employed (10 mL capacity) were placed into and Oreopoulou, 2011), the extraction of ␥-linolenic acid from an oven; each cell was filled with the corresponding amount Spirulina (Golmakani et al., 2012) and with the fractionation of of solid sample. After loading the sample into the extraction edible oil compounds (squalene and tocopherol) (Hernández cell, the cell was filled with the corresponding solvent up to a et al., 2011; Vicente et al., 2011).

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