The Science of Coffee Measurements

  The Science of Coffee Measurements is a two-year research project designed to revise and update fundamental aspects of coffee brewing science. Conceived and executed by a team composed of chemists and sensory scientists. Brewing requires three key metrics that impact water extraction of coffee flavor: total hardness (GH), transient hardness (KH) and alkalinity (KH). Together these help the water extract the flavor from coffee beans. Water Temperature Water is one of the key ingredients in crafting great coffee, and getting its temperature exactly right is crucial to creating delicious cups. An optimal temperature range should be between 195-205 degrees Fahrenheit depending on which brewing method you are employing. No matter if you prefer drip or pour-over coffee brewing methods, too cold of water will result in thin or overly bitter coffee while too much hot water could extract undesirable flavors and oils from your beans. As such, The National Coffee Association advises boiling your water to between 195-205 degrees Fahrenheit before pouring it over your beans. Temperature of water has an effect on coffee flavor by altering how quickly its constituent components are extracted into a brew. As faster extraction occurs, more of its soluble components will come to the fore and result in a bitter and unpleasant flavor profile. Measuring water temperature requires several different approaches; you could either use a traditional thermometer, or invest in a smart kettle that will maintain its target temperature until you need to use it. To achieve optimal results, it's recommended that you utilize a high quality thermometer with an infrared laser feature that allows you to accurately gauge water temperatures from afar. A gooseneck kettle may also help ensure you brew at an ideal temperature every time. An accurate thermometer is an indispensable asset to any serious coffee enthusiast, though there are also smart kettles with integrated thermometers that automatically bring water up to its ideal temperature when it's time for you to brew - all you have to do is press start! While these models can be costly, they do a fantastic job at making sure water reaches the ideal temperature when needed for brewing. The National Coffee Association suggests a water temperature between 195-205 degrees Fahrenheit for optimal extraction, though this varies depending on your brewing method. Dark roasts tend to overextraction at lower temperatures; therefore it's wiser to choose slightly higher temps when brewing them at home. Medium and light roasts feature more soluble flavors that require slightly warmer temps during production. Brewing Time Coffee brewing is the process of using water and coffee grounds to transform them into liquid coffee. The water extracts and dissolves different substances found within ground coffee grounds such as acids, sugars, oils, and solid particles quickly while others take more time - for instance natural flavors in the coffee may dissolve rapidly. Brew time is key to producing delicious coffee as it determines how much of it will be extracted and dissolved from the ground. Too short a timeframe could result in underextraction (resulting in bitter coffee) while too long could cause overextraction (resulting in sour or salty tasting coffee). Ideal brewing temperatures should be 205 degrees Fahrenheit (96 degrees Celsius). A thermometer can help ensure you're brewing at this ideal temperature or simply adjust brew time and grind size appropriately. Brew time not only affects the amount of coffee extracted, but it can also alter the balance of flavor compounds extracted from ground coffee. Therefore, it is vital that an identical coffee type and method has an equal brew time across multiple iterations of brewing sessions. Filter methods make brew time improvement more complex; however, by using less coffee and grinding finer, this will still allow a faster flow rate of water through the grounds and alter its extraction profile. These effects are multidimensional, making filter brewing optimization more complex than full immersion methods such as drip or espresso brewing. For instance, adding more coffee will increase flavour concentration while decreasing flow rate through grounds. In a previous study, we conducted experiments to explore the influence of brew temperature on coffee extraction dynamics. We collected samples at various temperatures and adjusted grind size and brew time accordingly in order to meet target TDS and PE concentrations, as described in Supplementary Table S1 and Fig 1. These tests indicate that extraction dynamics are determined more by differences between TDS and PE than by differences in brew temperature; at least across our range of temperatures tested. Grind Size Grind size is one of the most essential coffee measurements - getting it wrong can leave you with bitter, acidic coffee that doesn't meet your preferences and tastebuds. Finding your ideal grind can help create custom brew recipes tailored exactly to you! Grind sizes range from fine to extra coarse, making it necessary to determine which grind size best matches the method and type of coffee being prepared. Knowing your grinder size is both crucial for successful brewing methods as well as for different varieties. Your ideal grind size depends on both how much time you have available to you for brewing and your desired style of brew - for instance, for French presses it will typically be coarser than when using single-serve espresso machines. Furthermore, when selecting the type of bean you want to use for grinding, it's also important to keep in mind its properties: lighter roasts tend to be more soluble and require finer grinding while darker roasts have lower solubility levels and should be ground coarser. Another way of looking at grind size is that larger and coarser pieces take longer to dissolve in water than finer ones; thus enabling better extraction and flavorful coffee with coarser grounds. Grind size also plays a factor in how the coffee reacts with its grounds; for instance, finer grounds produce stronger flavors while coarser grains result in lighter and subtler beverages. Consistent grind sizes are essential to achieving even extraction when brewing for espresso, and blade grinders tend to struggle in meeting this standard, leading to uneven extractions and even yields. Burr grinders utilize uniform pressure and rotation to essentially crush beans into an equally uniform grind without producing excess heat - making them the best option for producing consistent grinding sizes. Extraction Rate Coffee extraction is the practice of dissolving desirable compounds found in coffee grounds using hot water, such as caffeine, lipids, acids and sugars. The degree of extraction depends on factors like water temperature, brew time, grind size and quantity of grounds used. Extraction is key to creating a well-balanced cup of coffee. An optimally extracted cup will feature fruity and acidic notes, sweet or tart notes, as well as an enjoyable aftertaste and pleasant finish after drinking. Research by organizations such as the Specialty Coffee Association of America indicates that optimal extraction levels lie between 18% and 22%. Under-extracted coffee will lack the fruity and acidic notes that make it so enjoyable, leaving a flat taste due to the early extraction of compounds responsible for these notes. As the flavors that create coffee's complex flavors aren't all extracted at the same rate, brewing your cup carefully allows you to tailor it exactly to your palate. Acids tend to dominate when they first emerge, leading to bitter or unpleasant tasting coffee if left unbalanced by other solubles. Over-extracted coffee will contain too much of the solubles that don't contribute to its flavor, and will taste bitter. Bitterness develops more slowly than its sour and sweet counterparts but can quickly take over if you lack an understanding of how to extract coffee correctly and ensure its taste remains optimal. An ideal extraction ratio can be attained through a grounds-to-water ratio of 1 gram of coffee to 16-18 grams of water, although you may require tweaking it until finding your ideal extraction ratio for brewing methods such as French Press. Increase the brew multiple for maximum extraction % or grind your coffee finer to increase surface area for the water to contact and extract solubles, respectively. These strategies will produce coffee that has more intense flavors with higher total dissolved solids concentration. Be careful of shifting too far towards the right side of the x-axis!