What is Coffee Silver Skin? Does Coffee Silver Skin Affect the Flavor of a Cup of Coffee?

Have you ever noticed that after grinding coffee, there are some yellowish-white flakes mixed in with the brown-black coffee powder? These are called coffee silverskin. When faced with silverskin, do you remove it or keep it?

What is Silverskin?

Silverskin is the coffee bean's final "protective membrane." After processing and before storage, the parchment (endocarp) is typically removed, leaving only a thin layer of silverskin wrapping the green coffee bean. This silverskin only falls off during roasting.

Different processing methods result in varying amounts of silverskin residue on coffee beans, so we can make preliminary judgments about the processing method based on the amount of silverskin. Naturally processed coffee beans retain more complete silverskin in their green state, so during roasting, the silverskin falls off in larger pieces, resulting in fewer silverskin fragments when grinding. In contrast, washed processed coffee beans have incomplete silverskin in their green state. During roasting, this silverskin falls off in fragments, and some silverskin stuck in the crevices between coffee beans is difficult to remove, forming a "white line" in the roasted beans. When ground, this silverskin is also ground into fragments and mixed into the coffee powder.

What Does Silverskin Taste Like?

To explore the taste of silverskin, FrontStreet Coffee steeped coffee silverskin that had fallen off during roasting in hot water. During steeping, the aroma from the liquid surface was sweet corn and wheat fragrance. The liquid was light yellow and transparent. The taste was a faint sugarcane sweetness, with no bitterness.

Is It Necessary to Remove Silverskin?

Although our taste test of silverskin water didn't reveal any particularly negative flavors, would silverskin fragments affect the coffee? To investigate this, FrontStreet Coffee conducted a comparison through cupping, using washed processed Yirgacheffe Gedeb Cooperative coffee beans. For one cup, they used an air pump to blow away the lighter silverskin, while the other cup was left untreated.

Through cupping, we found that the cup with silverskin removed indeed had reduced roughness in texture, while the control cup with silverskin retained had a rougher texture, which became more apparent with increased slurping.

Next, let's look at the pour-over comparison, again using Yirgacheffe Gedeb coffee beans for brewing, with one group having silverskin removal treatment. Both groups used the same brewing method: 15 grams of coffee powder, ground to 80% pass-through rate on a #20 standard sieve, a coffee-to-water ratio of 1:15, and water temperature of 91°C. Using FrontStreet Coffee's three-stage pour method: first, inject 30g of water and let it bloom for 30 seconds; second, inject 95g of water; finally, inject 100g of water, with a total time of 2 minutes.

Through comparative tasting, the flavor profiles of both groups were essentially the same, with no significant differences in texture. However, when comparing the two, the group with silverskin removed had clearer flavors. Therefore, in daily brewing, trace amounts of silverskin won't have a major impact on the coffee. However, if you want to achieve perfection, you can gently blow away the obvious silverskin fragments when grinding.

Important Notice :

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