A New Study Reveals the Relationship Between Coffee Roasting Levels and Caffeine Content
A recent comprehensive study has unveiled the impact of coffee roasting levels on the extracted caffeine content and its concentration in the final brew, challenging some common beliefs in the coffee industry.
Titled “Caffeine Content in Filter Coffee Brews as a Function of Degree of Roast and Extraction Yield”, the study was conducted by researchers at Berry College and Drexel University. They analyzed 30 different combinations of green coffee types, roasting levels, and extraction times.
The researchers utilized advanced techniques such as refractometry, high-performance liquid chromatography (HPLC), and scanning electron microscopy to explore the complex dynamics governing caffeine extraction.
According to experts, the relationship between roasting levels and caffeine content has long been a subject of debate. However, this study provides significant insights by isolating the factors that have often confused previous results.
The researchers arrived at several important findings, including:
- Caffeine content peaked at roasting levels with mass losses ranging between 14–16%, which corresponds to light to medium roasts. Darker roasts, however, generally exhibited lower caffeine levels.
- When comparing brews with the same extraction yield, darker roasts demonstrated higher caffeine concentrations, challenging the common belief that light roasts always contain more caffeine.
- As roasting progresses, coffee beans become more porous, enhancing extraction efficiency. However, this effect diminishes due to caffeine losses caused by volatilization at high roasting temperatures.
The researchers adopted a rigorous methodology to ensure accuracy and repeatability. Ethiopian coffee varieties, including natural (dry-processed) and washed (wet-processed) types, were selected for their diverse characteristics. Five different roasting levels were prepared using an advanced electric drum roaster (Aillio Bullet v2). Each roasting level was characterized using precise parameters such as color, density, and mass loss percentage.
The coffee was brewed using the AeroPress device under standardized conditions, including a water-to-coffee ratio of 15:1. Different brewing times (1, 2, and 10 minutes) were tested to observe variations in extraction yield. External factors such as grind size were controlled using sieving, and filtered water with consistent chemical properties was used to minimize external influences.
The study demonstrated that extraction yield—the percentage of soluble compounds extracted from ground coffee—plays a critical role in determining caffeine levels. Results showed a decline in extraction yields with increasing roast darkness, attributed to the breakdown of soluble compounds during roasting.
Interestingly, darker roasted coffee exhibited higher caffeine concentrations at the same extraction yield compared to lighter roasts. This is due to the lower presence of other soluble compounds in darker roasts, allowing caffeine to represent a larger proportion of the extracted material.
The study also highlighted the role of porosity in extraction dynamics. Using scanning electron microscopy, changes in porosity across different roasting levels were measured. The researchers found that coffee beans become more porous as roasting progresses, enhancing the efficiency of extracting soluble compounds during brewing.
However, the results indicated that extremely dark roasting leads to reduced caffeine retention due to the collapse of the internal structure of the beans.
The research did not only focus on caffeine but also investigated chlorogenic acids, which are important antioxidants. The study revealed that these acids decreased significantly with darker roasting levels, making lighter roasts a better option for those seeking their health benefits.
This study provides valuable insights for coffee enthusiasts on how their brewing choices impact caffeine levels. While light and medium roasts typically deliver higher caffeine levels under standard conditions, similar levels can be achieved from dark roasts if extraction parameters are optimized. Furthermore, the findings suggest that lighter roasts may retain more beneficial compounds, such as chlorogenic acids.
The study also addresses the inconsistencies in previous research on roasting levels and caffeine content. Earlier studies produced contradictory results due to variations in brewing methods, grind sizes, and water properties. By standardizing these variables, this research offers a more reliable framework for understanding how roasting affects caffeine.
These findings hold significant value for coffee professionals, from roasters to baristas. Roasters can adjust their profiles to balance caffeine retention with flavor development, while baristas can optimize brewing methods to extract desired compounds.
Additionally, the study aligns with the growing demand for transparency in specialty coffee, enhancing consumer understanding of the scientific aspects of their favorite beverage.
Despite its considerable contributions, the study opens the door for further research. Can different brewing methods, such as espresso or cold brew, yield similar results? How do other factors, like the altitude of coffee cultivation and processing methods, influence caffeine dynamics?
This groundbreaking research underscores the remarkable complexity of coffee, where every variable—from bean origin to roasting level and brewing method—shapes the final outcome. By uncovering the intricate dynamics of caffeine extraction, the study advances coffee science and empowers both professionals and consumers to make informed decisions.
As specialty coffee continues to grow in popularity, this study reminds us that there is always more to discover about the world’s favorite beverage.
