Flavor taints and faults of coffee. Part III.

I will introduce in this last series of educational articles three more bean defects. At the end of this article, I will also highlight some physical analysis procedures established by institutions (such as the SCAA) for classifying green coffees by bean defect type.

I will start with the withered bean, which is another plant-based defect. This type of bean is caused by climate change- specifically, by severe draught. The bean could not complete its development due to scarce water. It is identified by a pale and wrinkled appearance as well as low density. These beans bring a grassy, astringent, insipid and paper-like flavor to brewed coffee. These kinds of beans are mainly removed by devices that work with airflow, sorting them out by its low density.

The next defect is known as a floater because it has low weight. These beans were exposed at some point in the storage phase to broad swings in humidity, causing the beans to dry out and reabsorb moisture. This beans causes a watery flavor, with bitter and dirty notes, and its appearance is faded to bleached with white stripe. These beans are hard to remove because they are typically formed after the mill process, and therefore must be removed by hand prior to roasting.

These are known as insect damaged beans. We usually find these beans with one or two perforations only. Beans with multiple perforations are removed within the mill process by mechanical devices measuring density. The higher presence of these beans in a lot, the greater chance to perceive dirty and earthy taints in a cup of coffee. This damage is usually a plant-based defect caused by an insect called the Coffee Borer (Hypothenemus Hampei).

In addition to the defects mentioned above it is possible to find other bad beans, including shells coming out from a genetic disorder which causes having one half of the bean wrapping around the other. Another defect sometimes found is an empty husk that is a piece of dried cherry with no bean inside. It is also possible to find parchment, broken beans and foreign matter such as stones, nails and many others fun things; ask any roaster to share their stories about the trash and treasures found within green bean bags.

Before I concluded this series it is important to mention that institutions such as the SCAA, National Federation of Coffee Growers (NFC), Green Coffee Association (GCA) and others have established procedures to classified the quality of coffee by the defective bean content. I will highlight just two of them the SCAA system and the Colombian one. To apply any of the procedures mentioned above it is necessary to pull a sample from any lot of coffee. Once the sample is pulled it is important to properly prepare an analytical sample. The SCAA protocol established that 350 grams of coffee is needed to perform this analysis. The Colombian protocol established an analytical sample of 500 grams. Starting from the sample, beans with one or more defects are pulled out and carefully counted. Based on the attached table those beans are grouped and counted only as full defects. According to NFC, the green exportable coffee should not exceed 72 full defects where 12 of them belong to the primary group based on the information provided in table 1. For the SCAA a specialty coffee must not have any presence of full defects.

View table here.

-Andres Castro