Understanding Defects To Better Taste Your Coffee - Dustin Ryan Yu

From seeing Discord questions and reading feedback we’ve gotten from players, I’ve seen players ask about defects in roasted coffee beans. I’m here to write about this based on my coffee experience – hopefully this generates some discussion & also sheds light on any issues players see 

I’m Dustin (he/him) and am new to the Leaderboard team. I’ve worked in coffee for over 4 years, and have experience in mostly green (unroasted) coffee, ranging from coffee sourcing, to sales, to quality control. I acquired my Q Grader certification in 2018, and have worked at cafes, with roasters, at a green coffee importer, and now am with Leaderboard. I’ve always been interested in coffee education, so it’s great to have this platform to be a coach and write a (brief-ish) guide on coffee defects. 

We’ll look at the different types of defects, go into some specifics, and learn more about what to expect, how to identify these (based on appearance and taste), and how to navigate or mitigate these issues as Leaderboard players. 

It’s important to remember that defects are sometimes hard to identify and can also happen anywhere along the supply chain. These are not directly correlated with a roastery’s quality control or standards – please don’t assume something about a roastery based on a couple defects you find! 

Coffees defects can start during the agricultural stages of growing, all the way to the roasting side. Dividing coffee defects into 3 main categories could be a little easier: (1) Green coffee defects, (2) Roasted coffee defects, and (3) Roasting defects. We will be focusing mainly on (2) Roasted coffee defects here. The other two are not suuuuper related to Leaderboard on the player’s end, so we will be skipping them:

  • Appearance:
    • I find that quakers are probably the most common “issue” we see in roasted coffee. It’s identified visually by the difference in colour (a very light brown) with the rest of the coffee.
    • Why does this happen?
      • Quakers are generally a result of unripe cherries and/or lack of sugars. This can happen due to immature green cherries being mixed in (from just being unripe, or malnutrition from the tree/soil), or via insect and/or microbial attack. Roasting involves browning of sugars (AKA Maillard reaction), and lack of sugars results in a lighter brown colour than their other coffee buddies in the bag.
        • Immature/Malnutrition:
          •  Cherries ripen over days/weeks from green to yellow, to orange, to red, and finally to purple and then brown/rotting. Different varietals can be at peak ripeness at different stages, for example a Colombian Caturra is usually picked at the red stage, and Colombian Castillo should be picked closer to purple for maximum sweetness. During processing, sometimes a few green cherries get accidentally mixed in with the reds. After processing, there isn’t an easy way to pick out the seeds that were unripe.
          • Microbial/Insect attack:
            • Cherries can also be attacked by microbes such as fungus, and insects such as Coffee Borer Beetles (CBB). In a nutshell, these attacks involve consumption of sugars in the cherry, thus leading to lack of sugars in the end product prior to roasting!
        • How does it taste?
          •  It typically tastes of paper/cardboard/peanut husk, but quakers can also be like a wildcard. Sometimes they don’t taste like much and don’t affect your cupping or brew, but there are other times where one quaker can spoil a full pot or brew of coffee. These are usually due to insect or microbial attacks, and these coffee beans usually taste like mold, mushrooms, plastic/rubber, or phenolic/medicinal. Personally, I pick out quakers before grinding my coffee!

          • Appearance:
            • Shells/broken beans usually look like a hollowed out coffee bean (shell), and broken/chipped beans are usually fragments of whole coffee beans.
            • Why does this happen?
              • Shells usually happen due to genetic mutations and simply look that way after picking, processing, and drying for exportation. These are usually this shape prior to roasting, but are also hard to pick out of a roast because they look similar to other beans.
                • Broken beans can happen either at origin or after roasting: they can either be chipped or broken in the harvesting/depulping/drying process, or break upon impact after it is roasted and more brittle.
            • How does it taste?
              • Shells and broken beans usually roast slightly different in a roasting machine due to different density and size. Imagine frying small pieces of garlic with larger cloves of garlic together in the same pan – of course the small piece is bound to get burnt faster.
              • These smaller coffee pieces are harder to catch when weighing your beans, but if you look closely, there are sometimes darker smaller coffee fragments. This might affect your perception of “roastiness” in your cup!
              • You can ignore smaller fragments if they look similar in colour to the others though – most likely chipped after roasting. No big deal on these, not game-changers in my opinion!

              Minor/Major Insect Damage
              • Appearance:
                • Roasted coffee that has been damaged by an insect (usually Coffee Borer Beetles) usually have small holes in the seed that look like straight drill holes.
                • Why does this happen?
                  • CBBs usually drill into the coffee cherry and eat the nutrients, preventing the cherry from ripening. A major vs. minor insect damage is determined by the number of holes – if it has 3 or more it is considered “major”. You should not see majors very regularly as there are high standards for specialty coffee, and these coffees usually don’t end up in the hands of a specialty coffee drinker.
                  • How does it taste?
                    • For minor insect damage coffee, it affects the cup on very rare occasions. Major insect damage beans sometimes end up in our cups, it is usually best to take these out before you brew as it may affect your cup! These can also taste moldy, fungal/mushroomy/dusty, phenolic/medicinal, or plastic/rubbery.

                    • Appearance:
                      • A light coloured, shell-like skin, similar to a peanut skin.
                      • Why does this happen?
                        • Coffee seeds usually have an outer skin called a silverskin, which usually detaches during roasting. This is also called chaff, which usually is removed during the roasting process. The amount of chaff can depend on many variables, such as roasting machine (some pull more chaff out, some less), roasting style (less chaff in darker roasts), and coffee process (more chaff in natural process coffees typically, but it depends!).
                        • How does it taste?
                          • Chaff usually does not taste like anything when brewed in with your flavourful coffee beans. If the look of it bothers you, you can give it a light blow and they should all fly away beautifully. 

                          • Appearance:
                            • A very dark coffee beans compared to the rest of the beans in your bag. These are hard to miss when weighing out your individual brew portions, but are easy to miss when mixed in with millions of other bean buddies.
                            • Why does this happen?
                              • Since there are multiple moving parts within a roasting machine, sometimes beans get stuck in the drum and only shoot out on the next roast! These beans are “double roasted” and can sometimes be missed in packaging.
                              • How does it taste?
                                • Usually tastes like roastiness, charcoal, or burned organic matter. Make sure to pick these out before you grind your coffee!

                                Hope this was an easy-to-follow guide for what to pick out and what to keep in your cuppings/brews! Happy Leaderboard tasting 😉

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