What Is The Science Behind Coffee Extraction?

So you’ve always wondered why your morning cup of coffee tastes so incredible? Well, it all comes down to the science behind coffee extraction. You see, when you brew coffee, you are essentially extracting the flavors and compounds from the ground coffee beans. This process involves a delicate balance of temperature, time, and the right amount of water. In this article, we’ll explore the fascinating world of coffee extraction and discover the secrets behind that perfect cup of joe. Get ready to uncover the science that makes your mornings a whole lot brighter!

The Basics of Coffee Extraction

The Extraction Process

Coffee extraction is the process by which coffee compounds are removed from the beans and dissolved into water, resulting in the brewed cup of coffee that we enjoy. Extraction occurs when water comes into contact with the coffee grounds, releasing flavor compounds, oils, and acids in the process. The extraction process is influenced by various factors, such as grind size, water temperature, brewing time, and water-to-coffee ratio.

Components of Coffee Beans

Coffee beans are complex structures that contain various chemical compounds that contribute to the taste, aroma, and body of the final cup of coffee. The two main components of coffee beans are soluble and insoluble compounds. Soluble compounds, such as acids, sugars, and caffeine, dissolve in water during extraction and contribute to the flavor of the coffee. Insoluble compounds, such as oils and insoluble fibers, add body and mouthfeel to the brew.

Solubility of Coffee Compounds

The solubility of coffee compounds plays a crucial role in extraction. Each compound in coffee has a different solubility level, meaning that some compounds dissolve easily in water, while others require more time and specific conditions to dissolve. The grind size of the coffee, the water temperature, and the brewing time all affect the solubility and extraction efficiency of different compounds. Understanding the solubility of coffee compounds is key to achieving a balanced and flavorful cup of coffee.

Factors Affecting Coffee Extraction

Grind Size

Grind size refers to the particle size of the coffee grounds. The size of the grind impacts the rate at which water comes in contact with the coffee surface, affecting the extraction process. Finely ground coffee has a larger surface area, allowing for faster extraction. Coarsely ground coffee, on the other hand, has a smaller surface area and requires a longer brewing time for optimal extraction. Finding the right grind size for your brewing method is essential to achieving the desired flavor profile.

Water Temperature

Water temperature plays a crucial role in coffee extraction. Hot water helps to dissolve the coffee compounds, resulting in the extraction of flavors. However, water that is too hot can over-extract the coffee, leading to a bitter and unpleasant taste. Conversely, water that is too cold will under-extract the coffee, resulting in a weak and watery brew. The optimal water temperature for coffee extraction is typically between 195°F and 205°F (90°C and 96°C), depending on the brewing method and personal preference.

Brewing Time

The brewing time refers to the duration for which water is in contact with the coffee grounds during the extraction process. The length of the brewing time affects the extraction rate of different compounds, as well as the strength and flavor of the final brew. Brewing for a shorter time can result in an under-extracted coffee, while brewing for too long can lead to over-extraction and a bitter taste. Finding the right balance in brewing time is crucial for achieving optimal flavors in your cup of coffee.

Water-to-Coffee Ratio

The water-to-coffee ratio refers to the amount of water used in proportion to the amount of coffee grounds. The ratio of water to coffee can significantly impact the extraction process and the resulting flavor profile. A higher water-to-coffee ratio can result in a weaker brew, while a lower ratio can produce a stronger and more intense flavor. Experimenting with different water-to-coffee ratios will help you find the perfect balance that suits your taste preferences.

The Role of Water in Extraction

Water Chemistry

The chemistry of water plays a fundamental role in coffee extraction. Water contains minerals, such as calcium and magnesium, which can affect the taste and extraction efficiency. The hardness or softness of water refers to the mineral content present in the water. Hard water with high mineral content can result in an over-extracted and bitter coffee, while soft water with low mineral content may lead to an under-extracted and weak brew. Understanding the mineral content of your water can help you optimize the extraction process.

Effect of pH on Extraction

The pH level of water, which measures its acidity or alkalinity, also influences coffee extraction. Coffee compounds have varying solubilities at different pH levels, impacting their extraction. Most coffee compounds are soluble in slightly acidic water, typically with a pH between 6 and 7. Water with a higher or lower pH can alter the extraction process and affect the taste and quality of the coffee. Maintaining the right pH level of water ensures optimal extraction and balanced flavors in the brew.

Importance of Water Quality

The quality of water used for coffee extraction is crucial for achieving the best results. Ideally, water should be clean, free from impurities, and have a balanced mineral content. Unpleasant odors, tastes, or impurities in water can alter the flavor of the coffee and create off-flavors in the brew. Using filtered or purified water will help maintain the desired taste and prevent any unwanted effects on the extraction process.

The Role of Time in Extraction

Contact Time

The contact time refers to the duration for which water is in contact with the coffee grounds during the brewing process. Contact time directly influences the extraction rate and the strength of flavors in the final cup. Longer contact time results in increased extraction of compounds, leading to a bolder and more intense flavor profile. However, it is important to find the right balance, as over-extraction can result in a bitter taste. Adjusting the contact time allows you to tailor the strength and taste of your coffee to your preference.

Brewing Methods and Time

Different brewing methods require varying amounts of time for coffee extraction. For example, a French press typically has a longer brewing time compared to espresso, as it involves steeping the coffee grounds for several minutes. Pour-over methods, such as the V60 or Chemex, typically have shorter contact times. Understanding the recommended brewing time for your preferred brewing method is essential for achieving optimal extraction and the desired flavor profile.

Over- and Under-Extraction

Over-extraction and under-extraction are common issues in coffee brewing that can result in imbalanced flavors. Over-extraction occurs when coffee is brewed for too long or with water that is too hot, leading to bitter and astringent flavors. Under-extraction, on the other hand, happens when coffee is brewed for too short a time or with insufficient water temperature, resulting in a weak and watery brew. Finding the right balance between extraction time and brewing variables is crucial for producing a well-balanced and flavorful cup of coffee.

The Role of Temperature in Extraction

Optimal Extraction Temperature

The optimal extraction temperature for coffee is typically between 195°F and 205°F (90°C and 96°C). Within this temperature range, the flavors and aromas of the coffee compounds are efficiently extracted, resulting in a well-rounded and flavorful cup of coffee. Lower temperatures can lead to under-extraction, while higher temperatures can cause over-extraction and bitterness. Maintaining the right temperature throughout the brewing process is essential to achieve the desired flavors and balance in your coffee.

Effect of Temperature on Solubility

Temperature directly impacts the solubility of coffee compounds. Higher temperatures increase the rate of dissolution, allowing for faster extraction of flavors. However, excessively high temperatures can lead to over-extraction and the extraction of undesirable compounds, resulting in a bitter taste. Lower temperatures may result in under-extraction and a weaker flavor profile. Finding the right balance and temperature range helps optimize the extraction process and enhances the flavors in your cup of coffee.

Brewing Methods and Temperature

Different brewing methods have specific temperature requirements for optimal extraction. For example, espresso machines typically use water at higher temperatures, around 195°F to 205°F (90°C to 96°C), to ensure efficient extraction within a short brewing time. Pour-over methods, such as the Hario V60, usually involve using slightly lower temperatures, around 195°F (90°C), for a longer brewing time. Understanding the recommended temperature range for your chosen brewing method is crucial for achieving the best extraction and flavors.

Understanding TDS and Extraction Yield

Total Dissolved Solids (TDS)

Total Dissolved Solids (TDS) refers to the measure of all the soluble compounds extracted from coffee and dissolved into the final brew. It includes a wide range of compounds such as sugars, acids, oils, and minerals. TDS is typically measured as a percentage, indicating the concentration of dissolved solids in the coffee brew. TDS affects the strength, body, and overall flavor of the coffee. The optimal TDS range for coffee is usually between 1.15% and 1.35%.

Measurement of Extraction Yield

Extraction yield refers to the percentage of coffee compounds extracted during the brewing process. It is a measure of the efficiency of extraction and is commonly calculated using the Coffee Extraction Yield formula. Extraction yield is influenced by various factors, including grind size, water temperature, brewing time, and water-to-coffee ratio. Monitoring and adjusting the extraction yield can help achieve consistent and well-balanced flavors in your coffee.

Optimal Extraction Yield

The optimal extraction yield, also known as the “coffee brewing sweet spot,” typically falls between 18% and 22%. This range ensures that desirable flavors are fully extracted while avoiding over-extraction or under-extraction. Achieving the optimal extraction yield requires careful attention to brewing variables and a balance between grind size, water temperature, brewing time, and water-to-coffee ratio. Experimenting with these factors will help you find the perfect extraction yield for your desired flavor profile.

Chemical Reactions and Coffee Flavor

Maillard Reaction

The Maillard reaction is a chemical reaction that occurs during coffee roasting and brewing, contributing to the development of flavors and aromas. It involves the interaction between amino acids and reducing sugars at high temperatures, resulting in the formation of new compounds. The Maillard reaction produces a wide range of flavor compounds, such as those that give coffee its caramel and chocolate notes. Controlling the Maillard reaction through careful roasting and brewing allows for the development of complex and desirable flavors in coffee.


Caramelization is another chemical reaction that occurs during coffee roasting and brewing. It involves the breakdown of sugars at high temperatures, leading to the formation of brown-colored compounds. Caramelization plays a significant role in the development of sweetness and richness in coffee flavor. The degree of caramelization depends on the roasting level and brewing parameters, such as temperature and brewing time. Balancing caramelization with other flavor components contributes to the overall taste profile of the coffee.

Acidity and pH

Acidity is an essential characteristic of coffee flavor, contributing to its brightness and complexity. The acidity in coffee comes from organic acids, such as citric acid, malic acid, and quinic acid. These acids provide a pleasant tartness and fruitiness to the brew. The pH level of the coffee affects the solubility and extraction of these acids and influences the perceived acidity of the coffee. Balancing the acidity and pH of the brewed coffee is crucial for achieving a pleasant and well-rounded flavor profile.

Role of Sugars

Sugars present in coffee play a significant role in flavor development, sweetness, and body. During the roasting and brewing process, sugars undergo various chemical reactions, such as caramelization, Maillard reaction, and fermentation, leading to the production of desirable flavors. Different types and amounts of sugars present in coffee contribute to the sweetness and complexity of the brew. The balance between sugars, acidity, and other flavor components creates a harmonious and enjoyable coffee flavor.

The Balance of Extraction


Bitterness is one of the key taste attributes in coffee. It is primarily caused by over-extraction, where undesirable compounds are extracted from the coffee grounds. Factors such as water temperature, brewing time, and grind size can impact the level of bitterness in the final cup. Achieving a balanced extraction that limits excessive bitterness is essential for creating a pleasant and enjoyable coffee experience.


Acidity in coffee refers to the bright and vibrant flavors that contribute to its overall taste profile. It is a desirable characteristic that adds complexity and liveliness to the brew. Factors such as coffee origin, roast level, brewing method, and water pH influence the acidity levels. Balancing the acidity with other flavor components is crucial for achieving a harmonious and well-rounded coffee flavor.


Sweetness is an important aspect of coffee flavor that provides a pleasant and enjoyable taste. It is influenced by the presence of sugars and the level of caramelization during roasting and brewing. Achieving the right balance of sweetness contributes to the overall flavor profile and helps create a more satisfying and balanced cup of coffee.

Body and Mouthfeel

Body refers to the weight, texture, and thickness of the coffee in the mouth. It is influenced by the oils, sugars, and other compounds extracted during the brewing process. A fuller-bodied coffee tends to have a richer and more velvety texture, while a lighter-bodied coffee feels thinner and lighter. Balancing the body and mouthfeel is important for creating a satisfying and enjoyable coffee experience.

The Influence of Brewing Methods


Espresso is a brewing method that involves forcing hot water through finely ground coffee under high pressure. It produces a concentrated and full-bodied coffee with a rich flavor and crema layer. The short contact time and high pressure in espresso extraction result in an intense and flavorful brew. Espresso brewing requires precise control over variables, including grind size, water temperature, brewing time, and pressure, to achieve optimal extraction and balance in flavor.

Pour Over

Pour-over brewing methods, such as the V60 or Chemex, involve slowly pouring hot water over a bed of coffee grounds placed in a filter. The water drains through the grounds, extracting flavor compounds and creating a clean and nuanced cup of coffee. Pour-over methods offer more control over brewing variables, allowing for customization and experimentation. The brewing time, water flow rate, grind size, and pouring technique all impact the extraction process and the final flavor profile.

French Press

French press brewing involves steeping coarse coffee grounds in hot water and then pressing a plunger to separate the grounds from the liquid. This method allows for a longer contact time, resulting in a full-bodied and robust cup of coffee. French press brewing requires a coarse grind size and a longer steeping time to achieve adequate extraction. The resulting coffee retains more of the coffee oils, resulting in a rich and full-flavored brew.

Moka Pot

The Moka pot is a stovetop coffee maker that produces a strong and concentrated brew similar to espresso. It consists of a bottom chamber for water, a middle chamber for the coffee grounds, and a top chamber for the brewed coffee. As the water in the bottom chamber heats up, it creates steam pressure that forces the water through the coffee grounds and into the top chamber. The Moka pot brewing method requires a fine to medium grind size and careful heat management to achieve optimal extraction and flavor.

Methods to Improve Extraction

Adjusting Grind Size

Grind size is a crucial factor in coffee extraction. By adjusting the grind size, you can control the rate at which water comes into contact with the coffee surface and regulate the extraction process. Finer grinds allow for faster extraction, while coarser grinds require longer brewing times. Experimenting with different grind sizes will help you find the ideal extraction rate for your desired flavor profile.

Controlling Water Temperature

Water temperature significantly affects coffee extraction. Controlling the water temperature within the optimal range, typically 195°F to 205°F (90°C to 96°C), ensures efficient extraction and balanced flavors. If your water is too hot, you risk over-extraction and bitter flavors. If it is too cold, under-extraction and weak flavors may result. Using a kettle with temperature control or preheating water to the appropriate temperature helps maintain consistency in extraction.

Experimenting with Brewing Time

Brewing time plays a crucial role in extracting flavors from the coffee grounds. Adjusting the brewing time allows you to control the strength and intensity of flavors in your brew. Longer brewing times result in bolder and more robust flavors, while shorter brewing times produce lighter and milder flavors. Experimenting with different brewing times will help you find your preferred balance and achieve the desired flavor profile.

Water Quality and Treatment

Water quality is essential for maximizing coffee extraction and maintaining the desired flavor profile. Using filtered or purified water can help eliminate impurities and maintain a balanced mineral content. The purity and quality of the water directly impact the taste and clarity of the brewed coffee. Treating water to remove any unwanted tastes or odors can also enhance the overall coffee experience. Ensuring high water quality is a simple yet effective way to improve coffee extraction and flavor.

In conclusion, understanding the science behind coffee extraction is key to brewing a great cup of coffee. Factors such as grind size, water temperature, brewing time, and water-to-coffee ratio all play a critical role in the extraction process. The solubility of coffee compounds, water chemistry, and the balance of extraction variables contribute to the final flavor profile. By experimenting with brewing methods and techniques and paying attention to the various factors involved in extraction, you can elevate your coffee brewing skills and create a personalized and delicious cup of coffee.