The SCAA state that specialty green beans can have no more than 5 full defects in 350 grams of coffee – and no primary defects at all.
But what’s a primary defect? What do green bean defects look like? And how do they affect the final cup profile?
I visited Ricardo Villegas Wilkie of Tecnocafé, Bogota at his company’s lab to find out. Tecnocafé won four gold, three silver, and three bronze medals at the International Contest of Coffees Roasted in their Countries of Origin last year. They’ve been roasting specialty coffees for 11 years, and working directly with producers for one year. Here’s what Ricardo had to show me.
Sorting green coffee beans for defects. Credit: Tecnocafé
How Samples Are Analyzed in The Lab
Tecnocafé buy parchment coffee, and their first step is to analyze it green. They prepare 350g samples and hull and classify the beans by screen size – beans that are consistent in size will roast better. Next, the moisture (which should be between 11% and 12.5%), bean density, and yield factor (how many bags of parchment are needed for a 70-kilo bag of green beans) are measured.
Specialty Grading Specifications from the Roasters Guild. Credit: Angie Molina Ospina
Next, physical defects are identified. Tecnocafé follow SCAA (now SCA) guidelines for this: only 5 secondary defects, 0 primary, are allowed.
Primary defects include: full black, full sour, pod/cherry, large stones, medium stones, large sticks, medium sticks. Secondary defects include: parchment, hull/husk, broken/chipped, insect damaged, partial sour, floater, shell, small stones, small sticks, water damage.
Green coffee bean defects. Credit: Coffee Research
7 Common Green Bean Defects
There are many green bean defects, and some are easier to spot than others: we all know what a stick or stone looks like. Ricardo talked me through the two primary defects that are difficult to recognize – full black and full sour – and five common secondary defects.
Full Black & Partial Black Beans
Full black beans is a primary defect, while partial black is a secondary one. The beans are brown or black, shrivelled, and with the crack too open. Causes include over fermentation, over-ripe cherries, and not enough water during cherry development.
Full black beans are a primary defect; partial black a secondary defect. Credit: Angie Molina Ospina
Full Sour & Partial Sour Beans
Full sour beans are a primary defect, while partial sour is a secondary defect. They are a light to dark brown. These defects are caused by too long a wait between picking and depulping, an overly long fermentation process, or storing the beans while they have too high a moisture content.
Full sour beans are a primary defect; partial sour a secondary defect. Credit: Angie Molina Ospina
Broken, Chipped or Cut Beans
This is a secondary defect, normally caused by the depulping machine.
Beans broken by the depulping machine. Credit: Angie Molina Ospina
Another secondary defect, this is caused by coffee pests: the coffee beetle borer, the white stem borer, the coffee bean weevil, and so on. Coffees damaged the the coffee beetle borer (la broca) tend to be sour and earthy.
Insect damage, probably from la broca. Credit: Angie Molina Ospina
Unhulled beans is a secondary defect. It leads to an astringent, bitter cup. What’s more, the hull can become burnt during roasting, damaging other beans in the process.
Unhulled beans. Credit: Angie Molina Ospina
How to Decrease Defect Rates
Ricardo tells me that Tecnocafé is lucky to work with loyal and reliable suppliers. The amount of green coffee defects he sees is minimal. Despite this, he pays close attention to what defects he does see and uses it to provide feedback. Producers can then improve their picking and processing methods.
It’s important to understand that each farm, and each country, is different. Some regions may be struggling with the coffee beetle borer; others could be facing drought or unexpected rains. All of these will lead to specific defects.
Roasters and buyers need to check for these defects before purchasing coffee – it’s keen to ensuring they receive high-quality beans and for giving feedback to farmers.
Ricardo reminds me, however, that what matters at the end of the day is the final cup. “Some coffees could have a good physical aspect, but… the taste in the cup is not appealing for me.” This is why green bean analyzing is only one of the many quality control processes in place for specialty coffee.
Written by Angie Molina Ospina, with thanks to Ricardo Villegas Wilkie, Jhonatan Arias, and Uber Camacho of Tecnocafé.
Perfect Daily Grind is not affiliated with any of the individuals or bodies mentioned in this article, and cannot directly endorse them.
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