Wednesday, July 1, 2009

Coffee 100 (6/27 & 7/4/2009 @ 10am, noon & 2pm)

Ok, grading green beans for the beginner coffee enthusiast.

Size: Acceptable sizes are generally considered 13-18 mm. Larger beans are considered more robust with flavor, so ideally your sample has a higher concentration of larger beans. How do you know this in any reasonable time frame? Glad you asked, no it's not by using a micrometer and hand measuring each bean individually! Some clever person figured that taking a piece of metal and puncturing it with 13mm and the next with 14mm, and so on until all acceptable sizes are had. Then you take your sample from the smallest size to the largest, counting or more preferably weighing each group you can assign the percentages per size. Sizing complete!

Defects: some defects are obvious, and that's where we'll spend our time. Fragmented beans, malformed, insect attacked and discolored. Broken or fragments are pretty easy to pull aside. Malformed beans again are pretty straight forward, with little practice you'll find most of them. Shells are the easiest malformed type to find, they are essentially the bean forming so that it is hollow with an opening, like a shell. Insect attacked beans often have small bites taken out of the bean and are surface based. Some insect damage can look like a fragment, with an irregular edge or serrated from the biting. Discolored beans to focus on will be the blacks, half blacks and or pale green's which often indicates a problem with the drying process. Also pay attention for shiny beans another common washing/drying problem.

Now, it's good to take a decent sample, say 50 grams. This is enough to grade, but not so tedious you'll want to give up. It's great to have 6 identical dishes to sort into, when you're done you'll weigh each group to get the defect %. The 6 bowels you'll identify as 12mm, 19mm, Fragments, Malformed, Insect and Discolored.

In the end you'll have three sets of numbers that will indicate the quality of you green bean sample, which directly translates into what ends up in your cup. The first number is the the % of outlier beans in size, so any beans smaller than 13 mm and larger than 18 mm as a percent to the total weight. SThe second indicator is the total defect % by weight by adding up all 6 dishes against the total weight. Finally you have a related set of numbers and those are the 4 individual % of total weight for the non-millimeter defects.

Now before someone cries wolf and cites one of several sanctioned methods, let me remind you that this article is intended for begginers. To give them their first exposure to identifying a good green bean to purchase as green or as roasted. I'll write additional Green Bean Grading articles that will conform to a standard in the future.

Depending on how dedicated, obsessed or just in the pursuit of the best cup, you'll do this for all of your green bean lots and discard the defects. This also will eventually make your supplier better if you share your results with them!

Good luck and have fun,

the BeanGuru