This article originally published in The Sturbridge Times, September 2020 By Elvis Dyer, Owner/Roaster, Sturbridge Coffee Roasters
While most people are consumers of coffee, many are unfamiliar with just what is in the cup, and the multiple steps and intricate process to get from the farm to your cup. Once that bean is grown, grading and screening are important aspects relative to the roaster getting the best bean to ensure your coffee has the great taste you love. Coffee roasters focus on consistency throughout the process and making sure the beans are consistent in size and quality within a lot is one of the first steps after making sure the bean is a quality bean from the start. Larger beans roast slower than smaller ones, so if there are different sized beans in the same selection, it is difficult to get a consistent roast.
Screening the Beans
Consistency in size comes down to screening the beans. Before being exported from its originating country, coffee is screened. Processors use screens to sort the beans by size. The beans are sifted through these screens, which are metal sheets with specifically sized, round holes punched into them. Screens are numbered 8 through 20, with the number referring to how many 64ths of an inch the holes are. For example, a size 8 screen has holes that are 8/64-inch-wide, and a size 20 screen has holes that are 20/64-inch-wide.The size of a selection is determined by passing it through screens until it doesn’t go through the next-smaller size. In its classification, the Specialty Coffee Association of America (SCAA) permits a 5% variance and other organizations allow similar or smaller variances.
Coffee beans are largely divided into Robusta, which is a lower-quality bean often used in instant coffee, and Arabica, the smooth, mild-tasting, higher-quality bean. Arabica is graded from high — the beans grown at altitude which are wet processed — to lesser quality, farmed at lower altitudes and dried in the sun. Traditionally, even-numbered screens are used for Arabica selections, and odd-numbered screens are used for Robusta. Therefore, an Arabica lot that was graded at screen size 18 might technically be 17/18, since the next-smallest screen used for Arabicas is usually size 16.
Coffee is sorted by size in its originating country, therefore the size is usually expressed using local terminology. What that means is that while you may see a coffee described as “screen 17/18”, it may also be called “Superior” in Central and South America, “Supremo” in Colombia and “AA” in Africa and India. Larger beans are associated with higher quality as they have a longer maturation period which often leads to more flavorful beans. Generally, screen size 16 and 18 are the highest quality coffee beans and anything smaller than 14 would be a lower quality (and inexpensive) grade.
Grading Coffee Beans
Green coffee is often graded according to the seriousness of the defects, both primary (for example a sour bean where the coffee has been overly fermented or organic matter mixed in with the coffee) and secondary (for example a broken or insect-damaged bean). To qualify as a specialty coffee, the beans have to be graded by certified coffee tasters - Q graders.
Using the SCAA system, the coffee can then be graded from one to five, with specialty coffee with no primary defects being Grade One.
These five grades include:
Specialty coffee (Grade One): To achieve this status, a 300-gram coffee sample must have beans +/- 5% of the same screen size, no primary defects, 0-3 secondary defects, 0 quakers (unripe beans), and a distinct unifying attribute be it taste, acidity, body or aroma.
Premium coffee (Grade Two): Similar to Grade 1 coffee, however, it allows for 3 quakers and 0-8 secondary defects. Grade 2 coffee is the most widely available high-quality.
Exchange coffee (Grade Three): These have at least 50% of beans above screen size 15 and a maximum of 5% below screen size 15. The beans must be free from faults, may exhibit 9-23 secondary defects, and 5 quakers. Grade 3 beans are most commonly used for supermarket brands and by non-specialty coffee producers.
We would recommend you stay away from any Below Standard Grade Coffee (Grade Four) and Off-grade coffee (Grade Five) beans as they are extremely sour and unpleasant to drink.
Grading and sorting are just two of the things that go on behind the scenes. Specialty coffee goes beyond the quality of the beans – the processing, roasting and brewing process is equally important to have a great coffee experience.
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