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Caffeine Content of Dark-Roast Coffee

author image Gail Morris
Gail Morris has been writing extensively since 1997. She completed a master's degree in nursing at Indiana University-Purdue University Indianapolis and practiced in medicine for more than 20 years. Morris has published medical articles in peer-reviewed journals and now writes for various online publications and freelances for Internet marketers.
Caffeine Content of Dark-Roast Coffee
Dark roasted coffee beans spilling from a canister. Photo Credit: AllegressePhotography/iStock/Getty Images

It wasn't until Starbucks opened its first store in the 1970s that individuals began to use coffee as a dessert or snack and not just a functional method of increasing alertness. It is the caffeine in dark-roast coffee that has central nervous system effects, causing an increase in alertness and productivity. Caffeine is naturally found in the beans roasted to produce coffee. However, the amount of caffeine in coffee depends on several factors, one of which is the length of time of the roast and the color of the bean.

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Definition of Caffeine

Caffeine is the ingredient in coffee that may help improve your productivity and mental focus, but also has some significant side effects. Consuming high amounts of caffeine every day, such as 600 mg or the equivalent of six cups of coffee, can lead to anxiety, restlessness and sleep disorders. Other side effects include irritability, jitteriness and headaches. Caffeine is a central nervous system stimulant that works on the brain by taking the place of adenosine, a neurotransmitter.

Roasting Differences

Coffee beans are harvested and then chemically processed and roasted to produce coffee. The roasting process helps create, balance or alter the flavor, acidity and body of the coffee bean. There are several stages in coffee roasting that cause the bean to double in size, change in color and often experience a weight loss. As moisture is lost in the bean, it suddenly will pop audibly, sounding a bit like popcorn. In this process, the starches are converted into sugar and the cellular structure of the bean is altered. Heating and roasting the bean releases coffee oil that is volatile and water-soluble. Once roasted, the flavor of the coffee bean can be damaged by moisture, light and oxygen. If the beans are roasted too dark, then the oils are burned; if too light, the oils do not precipitate and the coffee has a bitter flavor.

Caffeine in Dark Roast

The amount of caffeine present in coffee depends on several factors. Dark-roast coffee has more coffee oil precipitated from the bean, which includes more caffeine. The amount of caffeine is also related to the way in which the coffee is brewed and the variety of bean that was chosen for the coffee roast, according to For instance, 4 ounces of Arabica coffee beans produce 100 mg of caffeine when brewed in a drip method, while a 1-ounce espresso shot has 40 mg of caffeine. According to, a drip brewing method increases the amount of caffeine that reaches your cup.

Benefits of Dark Roast

Dark-roasting a coffee bean does not just impart greater flavor and more caffeine, but it also may create a compound in the coffee that reduces the amount of stomach acid you produce. A team of researchers published their work at a meeting of the American Chemical Society in 2010. They compared the chemical profiles of dark-roast coffee and light-roast coffee made with regular roasted and steam-treated beans. The dark-roast coffee had greater than 30 mg per liter of a chemical related to the reduced production of stomach acid, and was linked to less heartburn and fewer stomach problems.

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