What is the Coffee brewing control chart

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Coffee brewing control chart

You may think that preparing coffee is easy because you only need two ingredients, ground coffee, and water. However, it is not as simple as it seems, many factors affect the final result of the drink.

We can easily ruin the drink, obtaining bitter, acidic, little body flavors, among other unwanted characteristics. Finding the optimal balance is a complicated but not impossible job, to achieve this we need tools, one of them is the coffee brewing control chart. This tool allows us to know the strength and the percentage of extraction of our drink, in addition to other data.

Below we show you the coffee brewing control chart.

Its origin

In the 1950s, the Coffee Brewing Institute (CBI), under the direction of Professor Ernest Earl Lockhart of the Massachusetts Institute of Technology (MIT), conducted a series of studies where through tests Sensory evaluation, asked many coffee consumers about their preferences and with that data determined that there were certain common tastes.

Ernest Earl Lockhart

Professor Ernest Earl Lockhart.

Beverage samples were analyzed and a series of formulas developed. The study concluded that optimal coffee has a range of strength (concentration) between 1.15 – 1.35% of soluble coffee material in the beverage. The extraction (yield) was also analyzed and it was determined that the desirable extractions were in a range of 18 to 22% of the original weight used in the preparation.

With these values and with other data collected, Professor Ernest Earl Lockhart created the Coffee brewing control chart, a tool to record the consistency of the brewing process. This work laid the foundations for preparing good coffee and is still used today.

Coffee brewing control chart

Coffee brewing control chart.

Parts of the Chart

Parts of the Coffee brewing control chart.

Parts of the Coffee brewing control chart.

1. Strength.
It is located on the abscissa axis (Y-axis) of the chart, its range is from 0.80% to 1.60%.

Strength measures by the dissolved coffee solids in the beverage after preparation. In other words, it is the concentration of coffee in your cup.

The force is measured in Total Dissolved Solids (TDS), Parts Per Million (ppm) or mg / L, with the help of a tool called a refractometer.

Keep in mind that TDS measurements are not specific as to what dissolves, it is simply the dissolved substances. This means that 100 ppm of sugar and 100 ppm of salt, despite being different, will have the same TDS value.

Dissolved coffee solids include chlorogenic acids, esters, and caffeine, as well as organic acids such as citric, malic and lactic acids. These compounds are what make up the body, aroma, and flavor of a coffee and comprise the measurement of TDS of a coffee.

We can describe the force as strong or weak and the equation that defines it is:

TDS - Coffee brewing control chart

2. Extraction.
It is located on the ordinate axis (X-axis) of the chart, its range is from 14% to 26%.

The extraction yield is the total mass fraction of ground coffee that has dissolved in the beverage.

The extraction is responsible for affecting the flavor profile of coffee since different compounds dissolve in water at different speeds.

We can describe the extraction as underdeveloped (acidic or vegetable) or bitter and the equation that defines it for the percolation method is:

yield - Coffee brewing control chart
For other extraction methods such as immersion (French Press) or mixed (Aeropress, Claver or Siphon), the equation to calculate the extraction will be different and we will develop this topic in another article.

3. Brewing Ratio.
It is the proportion of water to use per unit of coffee. It can be expressed in the quantity of coffee per liter of water, for example, 60 gr / L is, 60 gr of coffee per liter of water.
The most commonly used expression is coffee: water, for example, the 1:15 ratio is 1 gr of coffee per 15 ml of water.

 

4. Strong – Underdeveloped.
The amount of ground coffee particles that have dissolved in the water is high and the ground coffee has not been sufficiently extracted, therefore, the final result of the drink is strong and underdeveloped.

 

5. Strong.
The amount of ground coffee particles that have dissolved in the water is high and the ground coffee has been extracted within the optimum balance range, therefore, the final result of the drink is strong.

 

6. Strong – Bitter.
The amount of ground coffee particles that have dissolved in the water is high and the ground coffee has been extracted for a longer time, therefore, the result is a strong and bitter drink.

 

7. Underdeveloped.
The amount of ground coffee particles that have dissolved in the water is within the optimum balance range and the ground coffee has not been sufficiently extracted, therefore, the final result of the drink is underdeveloped.

 

8. Ideal optimum balance.
The number of ground coffee particles that have dissolved in the water and what has been extracted is within the optimum balance range, resulting in a balanced beverage.

 

9. Bitter.
The amount of ground coffee particles that have dissolved in the water is within the optimum balance range and the ground coffee has been extracted for a longer time, the result is a bitter drink.

 

10. Weak – Underdeveloped.
The amount of ground coffee particles that have dissolved in the water is low and the ground coffee has not been sufficiently extracted, therefore, the final result of the drink is weak and underdeveloped.

 

11. Weak.
The amount of ground coffee particles that have dissolved in the water is low and the ground coffee has been extracted within the optimum balance range, therefore, the final result of the drink is weak.

 

12. Weak – Bitter.
The amount of ground coffee particles that have dissolved in the water is low and the ground coffee has been extracted for a longer time, therefore, the result is a weak and bitter drink.

How to use the chart

The first thing to keep in mind when making use of the chart is to define in which area you want your drink to be. With this already defined, the first data that this chart gives us is the coffee/water ratio.

For example, if we want our beverage to be in the ideal optimal Balance zone, the chart shows that there are 4 coffee/water ratios, 65, 60, 55 and 50 grams of coffee per liter of water or what is the same at 1:15; 1:17; 1:18 and 1:20 respectively.

Chart - Ideal optimum balance zone values

Ideal optimum balance zone values

However, with 4 coffee/water relationships, we have to define which of them we want to work with. What is desired is to get as close as possible to the ideal Optimum Balance point, if you establish that you want to work with the 1:18 ratio, with this data you can already know the amount of ground coffee and water that you are going to use.

Grind the coffee beans, use water at a temperature of 93°C ± 3°C and prepare the beverage with a percolation method. Once you have finished the preparation, use a scale to know the final weight of the drink and with the help of a refractometer determine the Strength (TDS).

With that data, you can now make use of the extraction equation.

yield - Coffee brewing control chart
If everything was done correctly, then the strength of the drink should be in the range of 1.20% and 1.30%; and extraction in the range of 18.5% and 21.7%. If not, then you will have to make some adjustments until the drink is within the desired ranges.
Chart - Optimum balance zone values ideal for a coffee / water ratio of 1:18.

Optimum balance zone values ideal for a coffee / water ratio of 1:18.

Keep in mind that this is an excellent starting point, but you may find that some coffees may taste better with higher or lower extraction rates.

Extraction Adjust

Almost always, it will be necessary to adjust the extraction so that our beverage is within the desired parameters. Playing with the extraction is where things get really difficult since there are many variables to consider, which makes preparing coffee an exciting challenge.

Next, we will show you the variables to correct or adjust the coffee better. As an adjustment is made, you should see in the chart in which area the drink is, in essence, it is, adjust and evaluate, as many times as necessary. Remember to adjust only one variable at a time.

 

Grinding size
The size of the ground affects 2 variables, the contact surface of the coffee with the water and the extraction time. Finely ground coffees have much more surface contact with water and their extraction time will be longer than medium ground coffees. This variable affects the extraction.

 

Preparation time
The extraction is directly proportional to the contact time of coffee with water.
The longer the coffee is in contact with the water, the more it will be extracted. Very long preparation time will over-extract coffee, very short preparation time will under-extract coffee.

 

Coffee/water ratio
You can increase or decrease the coffee/water ratio according to the strength you want to have in your drink.

 

Water temperature
Water temperature affects the amount of coffee that is extracted during preparation.
The recommended temperature is around 93°C ± 3°C, however, some coffee can have a very good extraction at temperatures below the recommended.

 

Agitation
How much or how vigorously stirring during the preparation process can have the effect of accelerating the extraction.

 

Water quality
There are two types of water, soft and hard. Soft water is one that contains fewer minerals and this tends to over-extract coffee. Hard water is one that has many minerals and this tends to under-extract coffee.

The coffee brewing control chart is an important tool, it allows us to know the amount of total dissolved solids in coffee, percentage of extraction, in addition to other data, which make coffee brewing interesting.

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