Jose Mollura & The Art of Detecting Coffee Defects

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Each week Moyee master roaster Jose Mollura talks about the triumphs and challenges of creating radically good coffee. This week: bean defects.

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Every specialty coffee company in the world is first of foremost in the business of detecting defects in their beans. It’s all part of quality control. One of the great things about my job is that I have the freedom to dive deep into the entire growing process. Last week when I was in Ethiopia I visited one of the country’s largest exporters to explore new blends for Moyee. In this stage of the process recognizing defects in beans is absolutely crucial. Actually, recognizing defects in coffee is something every coffee lover should know more about.

There are different types of coffee bean defects. Some defects are more serious than others, but if you don’t pay close attention when selecting your beans you will certainly taste the defects, or at least smell them, when it finally makes it into your cup.

There are four categories of defects you have to pay close attention to: field, process, storage and dried parts. Because I just returned from the beautiful fields of Jimma, I’ll focus today only on field-damaged beans and what it means. Each week I’ll tackle another category.


Field damaged beans

When we say a bean is field-damaged, we are talking about the coffee tree, the environment and microorganisms/insects. Yes, insects! The best coffee is grown in lush forests, after all.

1. Insect damaged beans

Some insects love to bore holes into the coffee cherries. The holes are tiny, so hard to detect, however these beans tend to be slightly darker than ‘unholy’ beans. To be honest, these have little influence on the resulting cup of coffee.


2: Dark brown beans

Boring into the cherry is one thing, sucking out all the juice from unripe fruit, like the Antestia bug does, is something else entirely. This too we can catch in the roasting stage. Its effect on the taste of the coffee all depends on how much juice that little bugger got.


3. Amber beans

This is a bean grown in soil with high PH. Don’t want that!


4. Shell of elephant bean

You will never find just one elephant bean, they always appear in groups of two or more. Even though they don’t significantly affect cup taste, they do make for an uneven roast.


5. Triangular bean

This is a genetic disorder that produces 3 beans per cherry. We avoid these.


6. Peaberry

This is also a genetic disorder that affects a single bean inside the cherry. Again, it’s not something you will probably taste in the cup. In fact, it doesn’t even affect the roast. But we do keep an eye out for them anyways. Perfection, remember?


7. Chips

Chips are caused by a nutritional deficiency in the growing process. You definitely don’t want chips in your beans, because it seriously affects cup taste and are really difficult to roast well.


8. Frost damaged beans

When you’re up in the beautiful Ethiopian countryside frost damage is pretty far from your mind, but it happens more often than you think (you’re high up, after all!) You can recognize a frost-damaged bean by its color: both inside and out the bean’s color moves from brown to black. If the damage is bad, it will more or less kill off the aroma, and we don’t want that.


9. Immature bean

There are all sorts of reasons a bean never properly matures – stress, insects, and drought, picked too soon. Immature beans should never make it to the roaster. They have increased bitterness and a very low level of acidity and flavor.


That’s it for Part 1 of this 4 part series over bean defects. And like I said, this isn’t serious coffee geeks stuff. This is the trick of every coffee trade, and it effects every single cup of coffee you drink. See you next week.




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