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[FOOD SAFETY & QUALITY]

by Neil H. Mermelstein

Coffee Quality Testing

offee is one of the most popular bever- the sun. In the wet method, the pulp is ages in the world. According to the mechanically removed and the is dried CNational Association (NCA), 58% with the parchment left on. The are of American consumers surveyed for its 2011 sorted by weight and size, fermented by nat- “National Coffee Drinking Trends” report ural for up to 48 hr to remove the said they had drunk coffee the previous day. mucilage, rinsed, and sun dried or machine It is available in numerous traditional and dried. The dried beans are called parchment gourmet varieties and blends and in many coffee. forms, including whole beans, ground, The beans processed by either method instant, and ready-to- beverages. It is are then sent to a mill for hulling, where the also available for in-home brewing in a vari- outer layers of the beans, including the ety of packages, including single-serving parchment, are mechanically removed; the packages such as packets and beans may be polished to remove any silver K-Cup® brewing cups, and it is used as skin that remains on the beans. The beans an ingredient in other products. are then sorted by size and weight, examined to remove any unacceptable beans, and & Processing graded on the basis of size, growing location Of about 60 species of coffee trees, two dom- and altitude, harvesting and processing inate world trade: Coffee arabica (referred to methods, and . The resulting beans, as Arabica), which constitutes 75% of pro- called green coffee, are bagged, stored, and duction, and Coffee canephora (called shipped to importing countries for roasting Robusta). from the three main grow- and grinding. According to the NCA, approxi- ing regions—Latin America, Southeast Asia, mately 7 million tons of green coffee is and Africa—have distinctively different fla- produced worldwide each year. A lot goes on behind the scenes to produce the full-bodied aroma and flavor of coffee from your favorite coffee beans. vor characteristics. Roasting at high temperatures (about Photo © iStockphoto.com/malerapaso The fruit of the coffee tree is called the 400°F) develops the aroma and flavor in the coffee cherry and is harvested when it turns beans and causes the beans to turn brown bright red. Within the cherry are two beans, and release the oil they contain. The roasts each surrounded by a thin, silvery membrane are generally classified into four categories. called silver skin. A parchment-like covering Light roasts are light brown with a mild flavor surrounds the two beans and is covered by a and no oil on the surface. Medium roasts At the roaster, the testing becomes a lot more rigorous, and the regional, national, and multinational coffee companies become much more involved in dynamic quality control.

thin layer of mucilage, a layer of pulp, and (also called American roasts) are medium skin. brown with a stronger flavor and no oil on the After harvesting, the beans are sorted surface. Medium-dark roasts are dark brown and cleaned by flotation to separate unripe, with a slightly bittersweet aftertaste and overripe, and damaged cherries and remove some oil on the surface. And dark roasts dirt, twigs, and leaves. Then they are pro- have a pronounced bitterness and a shiny, cessed and dried to a moisture level of about oily surface. Coffee beans are often blended 11% by either of two methods. In the dry before or after roasting to provide desired method, the beans are spread out to dry in flavor characteristics and then ground for pg 68 01.12 • www.ift.org brewing. The degree of grind varies extracting the from the with the brewing method that will be green beans with either water and used. Coffee for preparation in an activated carbon, a solvent such as machine is much finer than methylene chloride or ethyl acetate, that for drip brewing. or supercritical carbon dioxide. The Coffee is marketed in several coffee is later dried, roasted, general categories, ranging from blended, and so on. traditional/mainstream to specialty/ gourmet. Traditional/mainstream Evaluating Quality coffee, the everyday coffee sold for The quality of the coffee consumers mass distribution by brands such as drink depends on numerous factors, and Folger’s, con- such as the cultivar, growing alti- sists mostly of Arabica beans, is tude, climate, soil chemistry, readily available, can be obtained in harvesting and processing condi- large quantities, and looks and tions, drying method, storage the same every time. conditions (temperature, humidity), Specialty/gourmet coffee, marketed transportation method (container by such companies as and type and size), roasting conditions, Peet’s, includes high-quality beans grind size, packaging, age, and brew- with specific flavor attributes and ing method. Spencer Turer, Director identity, is purchased directly from of Coffee Operations at the indepen- farmers or cooperatives, and is dent coffee-testing company Coffee batch roasted in relatively small vol- Analysts (www.coffeeanalysts. umes. Coffee may also be com), said that testing is conducted concentrated and sold as liquid con- throughout the supply chain, but the centrate for use principally in amount of testing changes. foodservice or as an ingredient. Exporters and importers usually use Using the cupping method, Spencer Turer of Coffee Analysts evaluates the aroma Coffee is brewed in a drip coffee basic sensory and physical evalua- and flavor of coffee samples. maker, an , perco- tions to determine whether the lator, a /plunger, a Moka product meets their quality stan- all stages of production, the taster or stove-top octagonal Italian-style dards for grade and are free of “cupper” first evaluates the overall brewer, or a machine such as the sensory defects. At the roaster, the visual quality of the beans (grading Keurig K-Cup system, which uses a testing becomes a lot more rigorous, the beans for defects, size, moisture, pre-measured sealed disk or cap- and the regional, national, and multi- aroma, and color), then roasts a sam- sule. Instant coffee is made by national coffee companies become ple in a laboratory roaster, grinds the roasting and grinding coffee beans much more involved in dynamic qual- roasted beans, and evaluates the to a large size and extracting the ity control, using a variety of roasted coffee fragrance. The cup- aroma and flavor with very hot water instrumental analyses as well as per then adds boiling water to a in a countercurrent extractor. The sensory evaluation. Turer said that standard amount of the ground cof- coffee is concentrated in a thermal although many strides have been fee and allows the coffee to steep in evaporator or freeze concentrator, made in instrumentation for flavor the cup for about four minutes, which may include an aroma recov- and aroma detection and identifica- smells the aroma, breaks the crust of ery step, and is then freeze dried or tion, the simplest, least expensive, grounds to complete the aroma eval- spray dried. The result is a fine pow- and most replicable results in coffee uation, and then skims the floating der that might be further processed testing are obtained by sensory anal- grounds and oils from the top of the by steam agglomerating it to ysis, specifically the cupping method cup. After allowing the coffee to increase the particle size. for flavor and aroma. cool, the cupper tastes the beverage Decaffeinated coffee is made by In this method, which is used at by forcefully slurping a spoonful to

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Trade & Scientific Organizations Related to Coffee

Association for Science and Information on Coffee (www.asic-cafe.org). ASIC brings together global specialists working in the different fields of coffee science and technology, giving them the see if it meets expected stan- opportunity to present and compare their investigations. It encourages and coordinates research to dards, and then spits it out. contribute to better use of coffee and improvement of coffee quality. The 24th ASIC International Using this procedure, the Conference of Coffee Science will take place November 11–16, 2012, in San José, Costa Rica. cupper can evaluate the coffee Coffee Quality Institute (www.coffeeinstitute.org). CQI provides training and technical assistance sample quality and blend differ- to coffee producers and other individuals in the supply chain to increase the value, volume, and sus- ent beans for product tainability of high-quality coffee production. It also works toward creating systems and infrastructure development or to determine the that encourage a focus on quality and lead to higher farmer incomes. proper roast for specific flavor Green Coffee Association (www.greencoffeeassociation.org). This trade association provides characteristics. According to the resources and other benefits for individuals and companies dealing with the export, transport, stor- NCA, an expert cupper can taste age, insuring, financing, importing, trading, and roasting of green coffee. hundreds of samples of coffee a Institute for Scientific information on Coffee (www.coffeeandhealth.org). Founded in 1990 by day and still taste the subtle dif- major coffee companies in Europe, ISIC collects and evaluates studies and scientific information about ferences between them. Turer coffee and health, supports independent scientific research on coffee and health, and disseminates pointed out that the cupping pro- balanced scientific information. cess follows scientific protocols National Coffee Association of U.S.A. Inc. (www.ncausa.org). Founded in 1911, NCA is the leading to ensure that the only variable trade organization for the coffee industry in the United States. It serves all segments of the U.S. coffee in the test is the coffee being industry and focuses on market and scientific research, domestic and international government rela- sampled. All aspects of the pro- tions, issues management, public relations, and education. Its next national convention will be held cess are strictly controlled, March 22–24, 2012, in Charleston, S.C. including coffee roast parame- Specialty Coffee Association of America (www.scaa.org). The world’s largest coffee trade asso- ter, time between roasting and ciation, SCAA establishes quality standards; conducts research on coffee, equipment, and craft; and cupping, grind size, coffee por- provides education, training, resources, and other services. Its next annual symposium and exposition tion weight, water quality, water will be held April 18–22, 2012, in Portland, Ore., and will include a discussion about the next generation temperature, cupping vessels, of sensory analysis and implications for quality control, product development, and marketing. and so on. The cupper records the intensity and quality of the dry bean fragrance and the aroma, acidity, body, flavor, and Papers on Coffee Presented at IFT Annual Meetings finish of the beverage. Turer said that the physical laboratory tests that may be 2001 conducted on green coffee are “Coffee Adulteration and Analytical Approaches to Authentication” by C.W. Harrell of the Procter & density, moisture content and Gamble Co. water activity, bean size, grade 2006 (defect counts), and color. Tests “Effect of Ground Storage Time on Coffee Quality” by Carolyn F. Ross of Washington for roasted coffee are residual State University. oxygen and carbon dioxide 2007 within packages, moisture con- “Coffee Bitterness Assessment with the Electronic Tongue” by Michel Manach of Alpha MOS Inc. tent and water activity, roast 2009 color, grind particle size or bro- “Total Phenolics and Capacity of Coffee During the Roasting Process” by Alberto M. de ken bean counts, Azeredo of the University of Florida. dissolved solids, pH, and Brix/ “ Color Analysis” by Alberto M. de Azeredo of the University of Florida refractive index. Chemical test- 2010 ing for coffee includes “Coffee Roasting Color Kinetics” by Alberto M. Azeredo of the University of Florida. ochratoxin A, caffeine, nutrient “An Investigation of the Applicability of SIFT-MS in Process-Line Monitoring of Coffee Aroma” by analysis, microbiological analy- David Paterson of Syft Technologies. sis, and pesticides. Other tests “Coffee ( arabica) Quality Mapping in Honduras: Effect of Altitude on Green Bean Chemical that may be performed on Composition and Roasted Coffee Quality” by Francisco J. Bueso of Zamorano University. roasted coffee are caffeine, 2011 chlorogenic acids, lipids, carbo- “Comparison of Minolta, HunterLab, and Machine Vision in Assessing the Color of Roasted Coffee and hydrates, total polyphenols, total the Agtron/SCAA Coffee Roast Classification Standards” by Alberto M. Azeredo of the University , and mycotoxins. of Florida. Standard analytical methods for “Effects of Different Time-Temperature Conditions on Coffee’s Chemical and Physical Properties” by coffee have been published by Niya Wang of the University of Guelph. AOAC International (see table), the International Organization pg 70 01.12 • www.ift.org Coffee Quality Testing continued... for Standardization (ISO), and other AOAC Official Methods of Analysis for Coffee organizations. Norm Ouellette, Vice President, Method No. Title Method Global Quality Assurance at 920.88 Green Coffee Macroscopic examination procedure, Starbucks Coffee Co. (www.star- physical examination bucks.com), said that taste testing is 920.89 Coloring Matter in Green Coffee Identification procedure, sampling done at various stages of production: 920.90 Roasted Coffee Macroscopic examination, physical examination green beans selection and receipt, 920.91 Roasted Coffee Sample preparation roasting, grinding, and final bever- age. In the plant, the coffee is 920.92 Acidity (Total) of Roasted Coffee Titration roasted to the desired color, a deter- 920.93 Ash of Roasted Coffee Alkalimetric ammonium molybdophosphate method, minant of flavor, and then pulverized, gravimetric method, spectrophotometric method and the color is measured using light 920.94 Caffeine in Roasted Coffee Power-Chesnut method, gravimetric method reflectance instrumentation. The 920.95 in Roasted Coffee Infusion method, microscopy moisture content is determined after 920.96 Coating and Glazing Substances Munson-Walker general method, roasting since it affects quality and in Roasted Coffee polarimetric method, saponification No. shelf life. The flavor is spot-checked (Koettstorfer No.) titrimetric method by the cupping method during roast- 920.97 Petroleum Ether Extract of Roasted Coffee Gravimetric method ing and blending. In the grinding 920.98 Fiber (Crude) in Roasted Coffee Ceramic fiber filter method, digestion, process, the particle size is mea- gravimetric method sured using sieves. The grind is very 920.101 Starch in Roasted Coffee Munson-Walker general method, gravimetric method important as it affects the product brewed by the consumer. At the 925.14 Chlorides in Roasted Coffee Gravimetric method warehouse level, taste—and maybe 925.15 Sugars in Roasted Coffee Volumetric, electrolytic method color and moisture—is tested again. 950.40 Caffeine in Roasted Coffee Bailey-Andrew method, titration There is some use of gas chromatog- 957.04 in Green Coffee Spectrophotometric method raphy and high-performance liquid 957.05 Chlorogenic Acid in Roasted Spectrophotometric method chromatography to conduct other and Instant Coffee analyses, he said, but not much use of near-infrared spectrometry. 960.25 Caffeine in Roasted Coffee Micro Bailey-Andrew method, extraction, titration, digestion Ouellette said that high-perfor- mance liquid chromatography is used 965.25 Caffeine in Green Coffee Bailey-Andrew method, Kjeldahl method, titration, digestion a lot to analyze for caffeine content. Typical measurements on soluble 968.11 Moisture (Loss on Drying) Vacuum oven method I, gravimetric method in Roasted Coffee coffee include pH, solids estimation by Brix, and final product moisture 979.11 Caffeine in Roasted Coffee Chromatographic-spectrophotometric method content, which is very important for 979.12 Moisture (Loss on Drying) Vacuum oven method II, gravimetric method flavor and shelf life. Typical analyses in Roasted Coffee for liquid concentrate include mea- 973.21 Solids (Soluble) in Roasted Coffee Gravimetric method surement of solids concentration by 995.13 in Soluble (Instant) Coffee Anion-exchange chromatography with Brix, pH, and titratable acidity. pulsed amperometric detection He added that packaging is very 970.46 Aflatoxins in Green Coffee Thin-layer chromatography important for coffee quality. Coffee 975.38 Ochratoxin A in Green Coffee Thin-layer chromatography must be kept away from oxygen because the coffee oils oxidize very 988.16 Filth in Ground Coffee and Coffee Sedimentation, flotation, visual readily, causing the coffee to stale. Substitutes (Cacao Bean and Its examination, microscop Products/Chocolate,Coffee/ Coffee packages contain some resid- Ground Coffee, Press Cake) ual oxygen, and roasted coffee will 2000.09 Ochratoxin A in Roasted Coffee Immunoaffinity column high-performance release carbon dioxide, so packages liquid chromatography must be degassed and/or include a 2004.10 Ochratoxin A in Green Coffee High-performance liquid chromatography vent to release the internal pressure and also prevent oxygen from enter- ing the sealed container. Cans, metal Advances & Challenges standard protocols for assessing or , must have a good seal and When asked about advances in cof- quality. Another is that in the last low moisture and oxygen transmis- fee testing, Turer said that one is the two generations, the coffee industry sion rates. establishment of AOAC and ISO has made great strides in utilizing

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Coffee Quality Testing continued...

food science, including the use of Turer said that the major chal- do it differently. Testing protocols at instruments to evaluate roast color lenge ahead is providing consistent the exporters, importers, and roast- instead of the naked eye. Using the quality in spite of changes in ers may be different, but they should most contemporary technology pro- weather patterns and economics be internally consistent. The profes- vides greater efficiency, accuracy, that affect farmers’ productivity. sionals doing the sensory evaluation repeatability, and cost effective- Consumers don’t want to know that must do it the same way each time ness, he said. Another advance is weather conditions, increased so that the only variable is the qual- the general understanding of sen- insect or mold activity, or drought ity/characteristics of the coffee. sory evaluation and use of expert affected the amount of coffee pro- Ouellette said that as the panels and contemporary sensory duced or that the strength or demand for high-grade, high-grown, methods that are valid and credible weakness of the dollar is affecting really good Arabica coffee from a scientific perspective. farmers’ ability to buy equipment or increases, maintaining the quality of Ouellette said that sensory eval- fertilizer. Consumers simply want to green coffee will require improved uation methods continue to improve, open a package of coffee and see and sustainable agricultural prac- color-measuring instruments now that it looks, smells, and tastes the tices and methods for evaluating provide more information than same, he said. green coffee. Producers need to before, and automation and preci- He added that since there is no strive for good, consistent crop-to- sion of instrumental analyses are universal practice for farming and crop quality, which is not easy in increasing. He added that sophisti- harvesting coffee, the technologies agricultural production. FT cated instruments such as the used vary by country and culture, electronic nose may aid in product and the quality control testing dif- Neil H. Mermelstein, a Fellow of development but may not be cost- fers in different countries. Cupping IFT, is Editor Emeritus of Food Technology effective for day-to-day evaluation is the industry standard for sensory • [email protected] of coffee. evaluation, but different countries

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