Theoretical foundations of the coffee extraction process
The process of dissolving the flavors in coffee into the water via some method is known as coffee extraction. Three variables are required for each extraction process: first, coffee, second, water, and third, heat.
Water is an excellent solvent at the molecular level because it has a polar configuration consisting of two hydrogen atoms with a positive (+) charge on one side and an oxygen atom with a negative (-) charge on the other. Due to this, water becomes “hyper attracted” to a wide range of molecules. Other molecules’ bonds will be pulled away, leading them to disintegrate in water.
When water is heated, all of its molecules move faster, making it a more efficient solvent. As a result, when you mix coffee with hot water, the water dissolves the coffee’s distinct taste constituents. On the other hand, what are the chemicals and substances in coffee?
In a word, coffee extraction is the interaction of coffee with hot water for the compounds in coffee to dissolve in the water.
The following are the main components of coffee extract:
We can acquire many “things” together with water when extracting coffee with hot water (collectively called solvents). In terms of molecular weight, the lighter flavor molecules will enter the coffee extract first, followed by the heavier molecules, which will have the four categories of components listed below in order:
Enzymatic or Fruity Acids are the lightest flavor molecules dissolved early in the extraction process, giving coffee its fruity, acidic flavor.
Maillard’s Compounds: Ingredients produced during roasting as a result of the Maillard reaction (reaction between carbohydrate and Protein in coffee beans), commonly used to flavor beans (nutty), toasted grain, barley Nha (malty), smoked meat (barbecued meal), or even wood flavor.
Browing Sugar / Caramels: This group of sugars and caramels results from carbohydrate breakdown during roasting. Extracted after a sour taste and easily detectable in vanilla, chocolate, or caramel flavors.
Distillates (Dry): (Should not be translated as dry or distilled). When the Polyphenol molecules in your saliva attach closely to the Protein in your saliva, giving a dry, bitter taste, this results from the dark road roasting process. This is an unfavorable flavor element since it produces a harsh, intense smoke and ash sensation that is both unpleasant and long-lasting – fortunately, it is extracted last.
Caffeine is extracted relatively early; hence the caffeine extraction ratio is virtually always the same.
The concentration of the extract
The proportion (percent) of total dissolved solids in your coffee (Total Dissolved Solids) is the extraction concentration (TDS). When we say ‘extract concentration,’ we’re talking about the coffee’s flavor strength, and terms like strong, thin, heavy, or light (rich, watery, heavy, and light) are frequently used to characterize it. Describe this characteristic.
TDS = Mass of Soluble/Total Mass of Extract in percent
For example, a cup of espresso coffee has a concentration of 7 to 12 percent. That means the coffee cup contains 93 to 88 percent water, and the rest comprises soluble chemicals. This ratio is only in the 1-2 percent range for traditional brewing methods like Pour Over, which implies they contain 98.2 percent and 98.8 percent water.
Because a cup of Espresso can be ten times stronger than a cup of drip coffee, it will significantly impact your ability to taste the coffee’s inherent tastes (although coffee contains the same flavors, the taste is not the same). At varying concentrations, yours will interpret them differently). You could believe the roast is excessively dark at high Strength. Still, after diluting a cup of Espresso, you can taste characteristics developed by the roasting process that wasn’t noticeable before.
The extraction rate (also known as the extraction yield or solubles yield) is the proportion of the coffee’s components dissolved by water to the total volume of the coffee.
For example, if you use 20 grams of ground coffee to create Espresso, a 40-gram cup, and a concentration meter shows TDS = 10% (4 grams of solute dissolved in that cup), the extraction ratio (your EY) is 4g/20g = 20%; however, if you use instant coffee, the (EY) must be 99.99 percent.
Note: The best extraction ratio is 18-22 percent (dissolved coffee/total coffee weight).
If the extraction rate in your coffee cup is less than 18 percent (under extraction), the desired flavor components have not been extracted. The lower the extraction ratio, the fewer solutes have a chance to be removed at a later stage, resulting in an imbalanced flavor. On the other hand, if the extraction rate is higher than 22% (over-extraction), the coffee will be pretty dark and bitter, as undesired and difficult-to-dissolve tastes will have entered the mix.
Relationship between the concentration of the extract and the rate at which it is extracted
By accident, we don’t know the extraction rate (Ey) or the concentration of extraction (TDS) in a cup of Espresso. Typically, baristas use the Espresso ratio chart to determine the above numbers (photo below). To assess the concentration of solutes in the coffee, use a TDS measuring equipment (which can be measured with a Brix meter – also known as a refractometer) and then compute the correct extraction rate.
[Brewed Coffee(g) x TDS(percent)] = Extraction Yield (percent) / Ground Coffee (g)
You can easily calculate EY from TDS in a cup with EBR (ratio of powdered coffee/amount of Espresso achieved) using the chart (picture below). If you have a 32g Espresso cup made from 16g ground coffee, your brew ratio (EBR) is 2:1. If you look at the graph, you’ll notice that the 2:1 diagonal with TDS = 9% (vertical axis) correlates to EY = 18%. (horizontal axis).
Extraction Ratio Definition
Have you ever heard someone say that a cup of coffee is too weak or that Espresso is too strong? What criteria do you use to determine if coffee is strong, light, or balanced? Every day, we draw inferences about the flavor of coffee based on this, but very little thought is given to its tenets.
In a nutshell, following a slew of TDS hypotheses, Exy. If a cup of coffee has an Extraction yield of 18 – 22 percent, it’s probably “standard” and “excellent.” However, this is not the case in all circumstances. Because, regardless of whether the extraction yield is high or low, it is assessed based on the extracted flavors (Aroma and Flavor), not merely the formula used to determine based on Strength.
More specifically, a “strong” cup of coffee can be under-extracted in some situations (due to excessive TDS). The typical scenario is to take too much coffee and extract it quickly; at this point, the cup of coffee can be “strong” because many soluble substances are absorbed into the water in the first stage, but the composition of the extracts is not diverse because many compounds are left in the later stages of extraction.
Factors that influence the extraction of coffee
Temperature, preparation time, milling particle size, and, in a more convoluted fashion, the preparation process all influence extraction rate.
The extraction technique and the fineness of the coffee powder
Because the total contact area of finely ground coffee is significant, the compounds in the coffee dissolve more quickly when exposed to hot water. However, if the grind is too fine, the gap between the beans is narrower, allowing more water to infiltrate and making the coffee harsh (over-extraction).
If the grind is coarse and the contact surface is significant, the coffee beans will take longer to extract the ingredient. Because the grind size is so huge in the French Press, it takes 4 to 5 minutes to soak, but an Espresso machine with a fine grind takes only 20-30 seconds to extract. However, when the task is too coarse, the faster the water penetrates the coffee, the shorter the extraction period, resulting in a thinner and more acidic (under-extraction).
Furthermore, uniform grind size (Particle Size Distribution (PSD)) is critical because if you grind different dimensions simultaneously, the particles will be extracted unevenly, making taste challenging to create. Desire.
The temperature of the water and the extraction procedure
Temperature, or more specifically, water temperature, has a significant impact on the solute ratio in the extract. The dispensing temperature should be between 91 and 96 degrees Celsius, according to Kingston (2015).
Some of the dissolved chemicals that make up the tastes are not removed at temperatures below 90oC, resulting in a bland coffee. Some unwanted compounds, like bitterness, will be removed if the temperature is too high. As a result, we can alter the flavor of the coffee extract by modifying the temperature.
Time to extract coffee
Finally, the length of time it takes to extract the coffee significantly impacts its flavor (especially Espresso). The coffee will be sour, and the berry and fruit tastes will be more prominent due to the short extraction period (if any).
Coffee that has been brewed for a more extended period will be bitter. As a result, if you wish to cut down on bitterness, lessen the extraction time. However, if it is too short, it will result in a harsh sour taste.
Several aspects of the coffee extraction process
If we use a ratio of 1:16 (according to SCA, it should be 1:16 to 1:18) for pour-over (drip coffee), that means 15 grams of coffee will generate 240 grams of water. Then there’s Espresso, where the typical remix ratio is between 1:1 and 1:3. Of course, this ratio is dependent on a variety of factors, the most important of which is the purpose of your extraction.
For example, we frequently use a 1:1 ratio to reduce bitterness, also known as Ristretto, which means extracting the scents of fruits, seeds, etc., while leaving most of the savory, spicy, and smoky flavors behind.
Type of water: This isn’t a minor point because water makes up 94 to 98 percent of coffee extract. Therefore, we’ve only discussed the “minor” component of a cup of coffee in this article. It’s all right. We must additionally consider pH, alkalinity, and water hardness when dealing with this issue…