What is Coffee Silver Skin? Does Silver Skin Affect Coffee Flavor? Solutions for Excess Silver Skin in Coffee Grounds

Some readers have told FrontStreet Coffee that after grinding coffee beans into powder, there are many yellowish-white fragments mixed in with the grounds. What exactly are these fragments, and will they affect the flavor of the coffee?

The Last Layer of "Skin" on Coffee Beans

These yellowish-white fragments are actually silver skin, the last layer of protective film on processed green coffee beans. Just as peanut skin wraps around a peanut kernel, silver skin clings tightly to the bean while it is still green and doesn't easily fall off. After roasting, the silver skin separates from the bean body.

Why Are There Silver Skin Fragments in Coffee Grounds?

Although silver skin falls off during roasting, some beans retain a little of it. How much silver skin remains after roasting is closely related to the processing method of the beans. If you frequently buy different types of coffee beans, you'll notice that some have a "white line" down the middle while others don't.

You can refer to FrontStreet Coffee's image below. The left side shows naturally processed coffee beans, and the right side shows washed processed beans. Their biggest visual difference is that "white line" in the middle, which is actually the silver skin remaining on the beans.

Naturally processed coffee beans retain relatively complete silver skin in their green state, so the silver skin falls off more thoroughly, in pieces, during roasting, though trace fragments may remain. Washed processed beans, by contrast, don't have complete silver skin in their green state, so the silver skin falls off in fragments during roasting, and some of it stays in the crevices of the bean and is difficult to remove, forming the "white line" seen in the roasted bean.

So how much silver skin ends up in the final roasted beans has little to do with roasting technique; it mainly depends on the processing method of the beans.

Will Silver Skin Fragments Affect Coffee Flavor?

Many people worry that too much silver skin will affect the flavor of the coffee. FrontStreet Coffee once kept a skeptical attitude while verifying this question.

First, FrontStreet Coffee tasted the flavor of silver skin soaked in water, and the feedback was sweet corn, wheat, and sweetness, without any bitterness or other undesirable flavors.

Second, FrontStreet Coffee compared brewing with the silver skin removed against brewing with it retained. Through pour-over brewing, the feedback was that the two cups had basically consistent flavors with no significant differences. In other words, the silver skin remaining on coffee beans does not affect the flavor of the coffee.

FrontStreet Coffee Recommendation

Since the amount of silver skin you see in the grounds depends on the processing method, it helps to know how your beans were handled. FrontStreet's Kenya Tomato is an excellent example of washed processing done thoroughly. Kenya is known for its double washed method, and this bean from the Thika region is grown at 1,550 to 1,750 meters from the SL28 and SL34 varieties, then washed and soaked again and again to bring out its fruit. The result is a clean, juicy cup of cherry tomato, smoked plum, snow pear, and black plum, with brown sugar sweetness and a light green-tea finish.

For a gentler, more rounded washed coffee, try FrontStreet's Gutingding cooperative. Growers deliver their cherries to the cooperative for shared processing, and the traditional washed method, followed by a medium-light roast, lets it show jasmine florals and bright citrus acidity with green tea and honey notes, a clean and elegant cup for pour-over, cold brew, or espresso.