Evaluating the performance of a coffee machine is harder than it sounds. You need to know what good filter coffee is and accordingly Specialty Coffee AssociationThere are essential criteria for good brewing. Brewing time and water temperature are at the top of the list. Hot water should be in contact with the floor for a minimum of four and a maximum of eight minutes. The ideal water temperature range is between 197 degrees Fahrenheit (92 degrees Celsius) and 205 degrees Fahrenheit (96 degrees Celsius).
To see how well each coffee maker is up to the challenge, we log the length of their brew cycles. We also use thermocouple heat sensors connected to industrial grade data loggers. This allows us to record the temperature in the coffee grounds as they brew.
We measure the temperature in the brewing chamber of every coffee machine we test.
After preparing the coffee, we measure the coffee liquid produced using a sample measuring device optical refractometer. Taking into account the amount of water and freshly ground coffee, we can use this data to calculate the total percent dissolved solids for each brew. From there we get to the extraction percentage. The ideal range is generally considered to be between 18% and 20%.
We also back up the measured data with a good old-fashioned taste test. Over-extracted coffee tastes bitter and sharp, while under-extracted coffee is usually weak or sour. To be on the safe side, we run identical test runs at least three times to get an idea of
