Proper Coffee to Water Ratio
The ratio of coffee to water is the most important step in proper brewing and is
the one thing that can be done correctly every time. The volume of the carafe
can be measured to determine the volume. Since most measurement of ground
coffee at home is with the standard coffee measure this to can be relatively accurate.
The standard coffee measure is 1/8 cup by volume or one fluid ounce. One level
coffee measure is 7 to 8 grams or approximately 1/4 ounce. Be careful though
for some coffee measures supplied with coffee makers are not always a standard measure
and this too can be checked. If a scale is available this will result in the
most precise weight.
In the 1950's the coffee industry developed the Coffee Brewing Control Chart above.
The Coffee Brewing Center conducted numerous taste tests to arrive at a general
coffee-to-water ratio that produces the most flavorful coffee. The above chart
is available in grams per liter units of measure. Click here to go to coffee brewing control
charts. The one above is for brewing one half gallon of coffee with the weight
of coffee measured in ounces.
To best understand the control chart keep in mind that this chart is for brewing
1/2 gallon of coffee. The nine plots on the graph represent the line the brewing
process will follow based on the weight of coffee in the brew basket. If 4.75
ounces of ground coffee are placed in the brew basket and 1/2 gallon is used to
brew the coffee then the upper left most graph will be followed during the brewing
process. And like wise if 3.75 ounces is loaded into the brewer and 1/2 gallon
of water is used to brew the coffee the 3.75 oz. line located in the middle of the
chart will be followed during the brewing process.
At the beginning of the brewing process obviously there is nothing extracted and
the strength and extraction values are zero. The Control Chart is intended
for use at the end of the brewing process so the 3.75 oz. plot is not visible until
the strength has reached a value of 0.8% and the extraction has reached a value
of 14%.
The left vertical axis or y-axis coordinate of the graph is the concentration of
coffee in the brew water. This is a measure of the strength of the coffee
or Solubles Concentration. If too much coffee flavoring is added to the water
the coffee is too strong and if too little coffee is added then the coffee is too
week. The ideal brew will contain between 1.15% to 1.35% coffee flavoring
and the remainder water. This ideal strength range is highlighted horizontally
in yellow with the ideal strength in the center portion in green.
The horizontal axis or x-axis coordinate of the graph is the percent of coffee flavoring
compounds extracted from the ground coffee or Solubles Yield. This is a measure
of how much of the available flavoring is removed from the coffee and mixed with
the water. About 30 percent of the weight of ground coffee is soluble in water
and can be extracted during brewing. The idea range of extraction is 18% to
22%. After brewing this is all that should end up in the water. This
range of extraction is highlighted in the vertical yellow band with the ideal extraction
in the green portion in the middle. If too much flavoring is removed the coffee
becomes bitter and astringent and if too little is extracted the coffee is week
and under-developed.
If 3.75 ounces of coffee are placed in the brew basket of the brewer and 1/2 gallon
of water is used in the brewing process then as the coffee is brewed and the coffee
flavorings are extracted some amount of coffee flavoring will end up in the brewed
coffee at the end of the brewing process. The following example of how to
read the Coffee Brewing Control Chart will use the 3.75 oz. line on the graph.
The finished brew will end up somewhere along this line from the lower left corner
to the upper right corner of the graph depending on the result of the brewing process.
If the brewing process ends on the line in the lower left quadrant of the chart
the coffee will be weak and under-developed. Too little of the flavoring has
been removed from the coffee and add to the 1/2 gallon of water. This usually
happens when the brew process occurs too rapidly for the ground particle size used
to brew the coffee and not enough coffee flavoring has been extracted from the ground
coffee. Extraction of less than 18% will produce coffee that is weak and under-developed.
If the brewing process ends in the green box in the center of the graph the coffee
will be in the optimum range. Enough coffee flavoring has been extracted and
added to the 1/2 gallon of water. In this case the brew time is correct for
the ground particle size. The 1/2 gallon of brew water has extracted
between 18% and 22% of the available coffee flavoring.
If the brewing process ends in the upper right quadrant of the chart the coffee
will be strong and bitter. This corresponds to extracting too much of the
coffee flavoring and combining it with 1/2 gallon of water. This happens when
the ground particle size is too small for the brew time and over extraction occurs.
For some brewer designs the over and under extraction problem can be corrected.
If the coffee is over extracted increase the size of the ground particles
and if it is under extracted decrease the ground particle size. The rule of
thumb in the coffee industry is "the finer the grind the short the time".
In this example even though the correct coffee to water ratio was used the brewing
time can result in over extracted or under extracted coffee both of which produce
un-acceptable results. If the coffee is purchased pre-ground either decrease
or increase the brew time or purchase a finer or courser grind.
Regardless of what brewing equipment is used to brew the coffee the ground coffee
to water ratio remains the same. This is not to say that only one ratio is
right since personal preference is the final judge and the chart shows five lines
running through the Optimum Balance area of the chart. The ratio is however
a good starting point and adjustments can be made accordingly.
Below are some conversion tables to help in converting weights and volumes into
units of measure you are more comfortable with. To view other Coffee Brewing
Control Charts using liter and gram units of measure click here.
Also listed below are some equivalents of some common weights and volumes.
Other factors that affect the proper extraction of coffee flavoring are water itself,
the water temperature, the size of the ground coffee particles, the amount of turbulence
induced during the extraction process and the time of extraction. The amount
of control over any one of these parameters will depend on the type of brewing equipment
used to brew the coffee. See the coffee brewing examples to better understand
how to brew coffee using the different types of brewing equipment.
For the professional that must know more accurately the actual strength of the final
brew the use of a coffee brew analysis TDS meter can guide the adjustment of the
brewing parameters to achieve the correct extraction.
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