Caffeine Content in Coffee: A Comparative Analysis of Regular and Decaffeinated Varieties

Coffee is one of the most widely consumed beverages globally, with its popularity attributed to its flavor and caffeine’s stimulating effects. However, concerns about caffeine’s impact on health have led to the development of decaffeinated coffee.

You can certainly retrieve information describing the differences between caffeinated and decaffeinated coffee, but have you ever seen high-magnification images of the beans or what they look like under an electron microscope? This application note compares the electron microscope images and chemical composition of caffeinated and decaffeinated coffee.

Introduction

Coffee consumption has been integral to human culture for centuries, with an estimated 2.25 billion cups consumed daily worldwide (International Coffee Organization, 2023). The primary active compound in coffee is caffeine, a natural stimulant that affects the central nervous system—something we coffee drinkers are very aware of!

My daughter loves her coffee, and after a couple of large cups, she goes all day, whether it’s work or playing soccer. The effects of caffeinated coffee are pronounced. Unfortunately, this is less valuable for me as I am getting older and find my blood pressure bouncing to higher than-normal levels. So, going forward, I am relegated to decaf. Better for me and my heart. But I’m not here to proport decaf or the “high octane” stuff. I just want to share some of the imaging and differences we found in each coffee bean processed in our analytical lab.

Initial Observations Under An Optical Microscope

We first imaged both beans under an optical microscope, and the results are shown

Regular coffee bean Z-stack at 7.8X using Leica LED Ringlight, M205 stereo microscope and DMC5400 camera.
Decaf coffee bean Z-stack at 7.8X using Leica LED Ringlight, M205 stereo microscope and DMC5400 camera.
coffee bean imaged at 500x using Leica DM8000, brightfield, and Leica DMC5400
Decaf coffee bean imaged at 500x using Leica DM8000, brightfield, and Leica DMC5400 Camera.

It is difficult to tell the differences aside from color and slight texture variation, which could be caused by the decaffeination process. We can see more significant differences under the scanning electron microscope (SEM).

All the work was done on our Coxem EM40 tabletop SEM equipped with energy-dispersive X-ray spectroscopy (EDS) pictured below.

Preparing the Coffee Beans

The preparation process included fracturing the beans and applying a thin coat of gold in preparation for SEM imaging. The coffee bean is organic and non-conductive.

When the electron beam in the SEM interacts with the sample, it can cause charging effects, leading to image distortion and artifacts. Coating the sample with a thin conductive layer of gold helps dissipate the accumulated charge, improving image quality and enhancing surface topography details. The gold layer is extremely thin, usually amounting to only a few nanometers.

Once the preparation was completed, we were able to attain the following imaging results:

Regular Coffee at 1000x Mag SE detector.
Decaf Coffee at 1000x Mag SE detector.
Regular Coffee at 1000x Mag SE-BSE detector.
Decaf Coffee at 1000x Mag SE-BSE detector.
Regular Coffee at 5000x Mag SE detector.
Decaf Coffee at 2000x Mag SE detector.

Analyzing the Coffee Beans

The major difference between the regular coffee bean and the decaf bean seems to be that the decaf bean has thinner cell walls, likely due to the decaffeination process.

What is the decaffeination process?

The most obvious difference between regular and decaffeinated coffee is the caffeine content. A standard 8 oz (237 ml) cup of regular coffee contains approximately 70-140 mg of caffeine, depending on the bean type and brewing method (Reyes & Cornelis, 2018). In contrast, decaffeinated coffee contains only 2-12 mg of caffeine per 8 oz cup, with the FDA requiring at least 97% caffeine removal for coffee to be labeled as decaffeinated (FDA, 2022).

Several methods are used to remove caffeine from coffee beans, including the solvent method (using chemicals like methylene chloride or ethyl acetate), the Swiss water process (using water and activated carbon), and the carbon dioxide method (using supercritical CO₂) (Farah, 2012). These processes can affect not only caffeine content but also other compounds in the coffee.

Several methods are used to remove caffeine from coffee beans, including the solvent method (using chemicals like methylene chloride or ethyl acetate), the Swiss water process (using water and activated carbon), and the carbon dioxide method (using supercritical CO₂) (Farah, 2012). These processes can affect not only caffeine content but also other compounds in the coffee.

EDS Analysis of Regular Coffee Beans

Some additional results from the EDS analysis of the images show significant differences in these beans’ elemental makeup. Below is a spectral map of the elements present in the regular coffee bean.

Although small in proportion, we were able to identify some trace elements outside of the majority of Carbon and Oxygen. The most interesting being Rubidium (Rb), which, upon further investigation, identifies this bean as coming from Brazil. Rubidium is found in much of the soil in this part of the world, making it a unique identifier of foods grown in this part of the world.

EDS Analysis of Decaf Coffee Beans

Here is the spectrum of the decaf coffee bean. Notice that most of the trace elements found in the regular coffee bean do not register in the decaf bean.

The Results: Regular vs. Decaf Coffee Beans

What does this all really mean to us coffee drinkers? I would guess we are mostly interested in the health effects of decaf and caffeinated coffees, so here are the results of some additional studies.

Health Effects

Caffeine increases alertness, improves concentration, and boosts metabolic rate (Cappelletti et al., 2015). However, it can also lead to side effects such as insomnia, anxiety, and increased heart rate in some individuals, particularly those sensitive to caffeine or consuming high doses (Nawrot et al., 2003).

Health Benefits

Caffeinated and decaffeinated coffee have been associated with reduced risk of type 2 diabetes, liver diseases, and certain cancers (Poole et al., 2017). These benefits are largely attributed to the antioxidant content, suggesting that decaffeinated coffee offers many of the same health benefits as regular coffee.

Sleep and Anxiety

For individuals sensitive to caffeine or those with sleep disorders or anxiety, decaffeinated coffee provides a way to enjoy the flavor and ritual of coffee without the stimulant effects (Clark & Landolt, 2017).

Consumer Preferences

Some consumers report that decaffeinated coffee has a milder, less bitter taste than regular coffee. This is partly due to the decaffeination process, which can alter flavor compounds (Farah, 2012). However, advancements in decaffeination techniques have minimized these differences.

Psychological Factors

Psychological factors can also influence the perception of coffee’s effects. A study by Dömötör et al. (2015) found that even when given decaffeinated coffee, participants who believed they had consumed caffeine reported increased alertness, suggesting a placebo effect.

Conclusion

The primary difference between caffeinated and decaffeinated coffee is its caffeine content. While regular coffee provides the stimulant effects of caffeine, decaffeinated coffee offers a similar flavor profile and health benefits without the potential side effects of caffeine. The choice between the two often depends on individual health concerns, caffeine sensitivity, and personal preferences.

Future research should focus on refining decaffeination methods to preserve flavor compounds and antioxidants further. More studies are needed to understand the long-term health impacts of consuming both types of coffee. Regardless of the choice, both caffeinated and decaffeinated coffee can be part of a healthy lifestyle when consumed in moderation. And that’s the rub: moderation.

More studies should be done on drinkers who find it hard to moderate their intake. I’m just saying that drinking “ a lot” may be healthier than not. More antioxidants!

References

 

    1. International Coffee Organization. (2023). Coffee Market Report – January 2023.

    1. Reyes, C. M., & Cornelis, M. C. (2018). Caffeine in the Diet: Country-Level Consumption and Guidelines. Nutrients, 10(11), 1772.

    1. FDA. (2022). Spilling the Beans: How Much Caffeine is Too Much?

    1. Farah, A. (2012). Coffee Constituents. In Y.-F. Chu (Ed.), Coffee: Emerging Health Effects and Disease Prevention (pp. 21-58). Wiley-Blackwell.

    1. Ludwig, I. A., et al. (2014). Extraction of coffee antioxidants: Impact of brewing time and method. Food Research International, 61, 246-253.

    1. Toci, A., et al. (2006). Changes in the volatile profile and phenolic composition of espresso coffee during storage. Journal of Agricultural and Food Chemistry, 54(2), 374-381.

    1. Cappelletti, S., et al. (2015). Caffeine: Cognitive and Physical Performance Enhancer or Psychoactive Drug? Current Neuropharmacology, 13(1), 71-88.

    1. Nawrot, P., et al. (2003). Effects of caffeine on human health. Food Additives & Contaminants, 20(1), 1-30.

    1. Poole, R., et al. (2017). Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ, 359, j5024.

    1. Clark, I., & Landolt, H. P. (2017). Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep Medicine Reviews, 31, 70-78.

    1. Dömötör, Z., et al. (2015). Expectations and the effect of caffeine. Frontiers in Psychology, 6, 1359.

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