“Your Bean Needs to Apply Itself, Ms. Coffee”
No, you do not need to schedule a Teacher-Coffee conference, but some basic knowledge of coffee grading can help you get the best flavor for your dollar. There is no world-standard when it comes to grading coffee. Many countries create their own standards and these can vary. , but there are some basics that can be helpful.
Screen Size – Beans can be sorted by their size. Screen of varying sizes can be used to sort a crop by size. Generally, beans that are grown at the highest altitudes larger in size. Since coffee grown at higher altitude is generally recognized as being highest in quality, screen size can be a good basic indicator of quality. But more than that, beans of approximately the same size will roast more evenly. The screen sizes are indicated by 64’s of an inch, so a screen size stated as “17/18,” means that the beans are 17/64’s to 18/64’s of an inch which is about 7mm. A 15/16 screen is about 6mm, etc.
Screen size is widely used as a starting point for classifying coffee but it is only general in nature and does not necessarily translate into a flavor standard. There is a lot more to consider. Let’s take a look at the SCAA’s classification system to further define coffee classifications:
To grade a coffee, the person grading will first take a weighed sample of 300 grams of green coffee (about 1800 beans) to be classified and screen sort the sample for size rating and consistency. The beans are individually examined for defects. Defects can be a wide range of problems such as insect damage, broken beans, foreign matter (sticks, pebbles, etc.), husks, and more.
Specialty Grade Green Coffee (Grade 1): This is the highest grade of coffee. Specialty green coffee beans have no more than 5 full defects in 300 grams of coffee. No primary defects (large or medium stokes or sticks, black beans, beans still in in cherry state, etc.) are allowed. The beans are also rated by flavor after roasting. Specialty Grade must have at least one distinctive attribute in the body, flavor, aroma, or acidity. That is, they must be special. No quakers (beans picked prematurely and thus will roast improperly) are permitted.
Premium Coffee Grade (Grade 2): Premium coffee must have no more than 8 full defects in 300 grams. Primary defects are permitted. A maximum of 5% above or below screen size indicated is tolerated. Must possess at least one distinctive attribute in the body, flavor, aroma, or acidity. Must be free of faults and may contain only 3 quakers.
Following those grades are Exchange Coffee Grade (Grade 3): allows no more than 9-23 full defects in 300 grams. No cup faults are permitted and a maximum of 5 quakers are allowed. Below Standard Coffee Grade (Grade 4) allows 24-86 defects in 300 grams. Finally, Off Grade Coffee (Grade 5) will contain more than 86 defects in 300 gram. For those serious about coffee, these three grades are generally not considered when purchasing coffee.