Determination of the Elemental Composition of Coffee Using Instrumental Methods
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CORE Metadata, citation and similar papers at core.ac.uk Provided by Springer - Publisher Connector Food Anal. Methods (2013) 6:598–613 DOI 10.1007/s12161-012-9467-6 Determination of the Elemental Composition of Coffee Using Instrumental Methods Pawel Pohl & Ewelina Stelmach & Maja Welna & Anna Szymczycha-Madeja Received: 16 April 2012 /Accepted: 21 June 2012 /Published online: 14 July 2012 # The Author(s) 2012. This article is published with open access at Springerlink.com Abstract Although the content of elements in coffee is only Grembecka et al. 2007; Bertrand et al. 2008). Parts of coffee about 5 % (m/m), it seems to be a good indicator of the plants used in the food industry for the production of coffee coffee authenticity. Apparently, it can bring the useful infor- are fruits (berries) (Ashu and Chandravanshi 2011). Green mation about individual elemental patterns that are distinc- beans, collected from the dried and hulled berries, are tive to the origin of growing soils for coffee plants in roasted in a high temperature, i.e., 100–230 °C, to achieve addition to cultivation and environmental conditions used. a full aroma of coffee. This also results in a significant The elemental analysis of coffee by means of instrumental change in the color of beans from light to dark brown and measurement methods may have other uses. It can be used in the change of the chemical composition, especially the to prove the high quality and safety of raw coffee beans, fraction of volatile species (Belitz et al. 2009). various coffee byproducts, and the final coffee product in Coffee is consumed by around 40 % of the world's the market. Commonly, different atomic absorption and population (Mussatto et al. 2011; Oliveira et al. 2012). For emission spectrometry and instrumental neutron activation many people, especially in Western countries, the coffee analysis methods are used to determine concentrations of drinking is a part of their lifestyle and an everyday habit. various elements in green, roasted, and ground or instant The coffee beverage can be consumed for many reasons, coffees and coffee infusions, but these samples have to be including its stimulatory effects resulted from the presence suitably prepared prior to the analysis. of caffeine, rich phytochemistry, health benefits, and pri- marily excellent taste and aroma (Grembecka et al. 2007; Keywords Coffee . Elemental analysis . Atomic absorption Butt and Sultan 2011; Oliveira et al. 2012). Due to a habitual spectrometry . Optical emission spectrometry . Instrumental consumption of coffee, its chemical composition, namely neutron activation analysis . Sample preparation . Quality the presence of essential, non-essential and toxic elements, assurance and control has to be known and kept under control in terms of its safety, and to assists its quality, nutritional value, and certain sen- sorial properties (Krivan et al. 1993; De Nadai Fernandes et Introduction al. 2002; Zaidi et al. 2006; Filho et al. 2007; Oleszczuk et al. 2007; Oliveira et al. 2012). The authenticity of coffee relat- A plant named coffee is a shrub that belongs to the ed to its certain geographical origin and botanical variety Rubiaceae family, i.e., Coffea arabica (∼75 % of the world's based on the elemental analysis and statistical pattern rec- production), Coffea canephora, named also robusta (∼25 %) ognition methods seems to be quite important to producers and Coffea liberica (<1 %) (Martin et al. 1998a; Vega- and consumers (Krivan et al. 1993; dos Santos and de Carrillo et al. 2002; Zaidi et al. 2006; Filho et al. 2007; Oliveira 2001; De Nadai Fernandes et al. 2002; Fernandes et al. 2005; Filho et al. 2007;Grembeckaetal.2007; P. Pohl (*) : E. Stelmach : M. Welna : A. Szymczycha-Madeja Oleszczuk et al. 2007; Bertrand et al. 2008). This research Department of Analytical Chemistry, Faculty of Chemistry, activity could even include the differentiation of small ter- Wroclaw University of Technology, roirs, which components, mostly the altitude and the rain- Wybrzeze Stanislawa Wyspianskiego 27, 50-370 Wroclaw, Poland fall, significantly affect the elemental composition of coffee e-mail: [email protected] (Bertrand et al. 2008). Since consumers usually search for Food Anal. Methods (2013) 6:598–613 599 coffee with special taste and aroma, of a high quality and 2002; Villarreal et al. 2009; Hecimovic et al. 2011; Wei et al. produced from beans of known variety and origin, the 2011). These chemical species are often measured for the determination of the provenience of coffee is a very impor- purpose of discriminating coffee varieties and brands or tant part of the coffee trade (Martin et al. 1998a;Vega- determinting the coffee origin (Bernal et al. 1996; Costa Carrillo et al. 2002; Bertrand et al. 2008). Sometimes dis- Freitas and Mosca 1999;AndersonandSmith2002; honest producers can sell cheaper varieties or blends of Villarreal et al. 2009; Hecimovic et al. 2011). However, it coffees but recommending them as of a much better quality should be considered that all stages involved in the produc- (Anderson and Smith 2002). The difference between the tion of coffee, from coffee harvesting to roasting, can declared and the real composition can also be the effect of change the composition of the final product (Anderson and an accidental mislabeling (Martin et al. 1999). In all these Smith 2002; Mussatto et al. 2011). Among different sub- cases, the reliable and dependable analysis of selected com- stances present in coffee, only caffeine is stable to the ponents or properties of coffee may exclude such mistakes, excessive roasting temperature (Mussatto et al. 2011). i.e., fraudulent or accidental mislabeling and confirm the Other chemical compounds are susceptible to a degradation high quality of the final product (Suseela et al. 2001). during production and storage conditions (Anderson and This literature survey is devoted to different aspects of Smith 2002). the elemental analysis of relevant coffee products using Hence, a reliable and independent method enabling to atomic and mass spectrometry methods. Particularly, the differentiate the geographic growing origin of coffee has to attention is paid to suitable sample preparation steps for be focused on compounds that are stable during all coffee coffee products, quantitative measurements and quality con- production stages and a subsequent storage. Elements and trol and assurance manners. Practical applications of these their concentrations fulfill this requirement and for that analytical methods to the analysis of dry coffees and coffee reason the elemental analysis of coffee, aimed at determin- infusions and their results are thoroughly discussed. ing its elemental composition, is so important for the pur- pose of its quality control and bromatological value evaluation (Krivan et al. 1993; Anderson and Smith 2002). Elemental Coffee Analysis Samples and Their Pretreatment To guarantee stated quality and safety of a final coffee product and protect well-being and health of consumers, Green arabica and robusta coffee beans are directly taken different parameters responsible for the wholesomeness of from coffee plantations or coffee plantation cooperatives green beans, roasted beans, prepared coffee and its infusions (Krivan et al. 1993; Martin et al. 1998a, 1999; Filho et al. have to be measured using suitable analytical methods. For 2007; Oleszczuk et al. 2007; Bertrand et al. 2008;dos example, in the organoleptic analysis of green coffee beans, Santos et al. 2009, 2010). In a laboratory, coffee beans can their odor and taste in addition to the information about their be washed at first with tap water, followed by a neutral size, shape, color, and cross-section are ascertained as a part detergent, a diluted HCl solution and finally de-ionized of the quality assessment (Belitz et al. 2009). Color and water to remove soil particles and dust (dos Santos et al. flavor characteristics are important to find the best degree 2009). Next, they are roasted in a laboratory roaster and of roasting green beans (Belitz et al. 2009). For the evalu- ground to a fine powder (Martin et al. 1999; dos Santos et al. ation of the quality of coffee infusions, the flavor of pre- 2010). Otherwise, they can be dried over a desiccating pared beverages is commonly described under standardized substance or in ovens at temperatures within 60–103 °C conditions (Sanz et al. 2002). All individual notes of each and then pulverized in cryogenic mills or ground and pow- sample are collected and its unique profile is assessed, dered using rotor-type mills or grinders (Krivan et al. 1993; however, it should be noted that opinions of qualified coffee Martin et al. 1998a; Filho et al. 2007; Oleszczuk et al. 2007; testers on coffee taste and aroma can be subjective (Krivan Bertrand et al. 2008). et al. 1993; Anderson and Smith 2002). Roasted coffees (beans or ground beans) are usually Chemical methods of the coffee analysis are similar to purchased in local markets (Rajwanshi et al. 1997; those used in the food quality control and assessment Haswell and Walmsley 1998; Jaganyi et al. 1999; (Martin et al. 1998a). They are based on the determination Magalhaes et al. 1999;Martinetal.1999; Jaganyi and of different compounds, e.g., volatile compounds, caffeine, Madlala 2000; Anderson and Smith 2002; Vega-Carrillo et tannins and polyphenols, lipids, individual carbohydrates al. 2002; Krejcova and Cernohorsky 2003;Santosetal. like sucrose, glucose, fructose, arabinose, galactose, poly- 2004; Anthemidis and Pliatsika 2005; Fernandes et al. saccharides like cellulose, amino acids, vitamins B3 and PP, 2005; Zaidi et al. 2006; Filho et al. 2007; Grembecka et al. chlorogenic acid, trigonelline, and minerals (Bernal et al. 2007; Santos et al. 2008; Castro et al. 2009; Frankova et al. 1996; Costa Freitas and Mosca 1999; Anderson and Smith 2009; Ashu and Chandravanshi 2011). Powdered or ground 600 Food Anal. Methods (2013) 6:598–613 solid coffee samples are usually subjected to further stages (Suseela et al.