Evaluating the performance of a coffee maker is trickier than it might sound. You need to know what good drip coffee is and, according to Specialty Coffee Associationthere are important criteria for good brewing. Brewing time and water temperature top the list. The hot water should have contact with the grounds for at least four minutes and no more than eight. 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 meets that challenge, we record the length of their coffee brewing cycles. We also use thermocouple heat sensors connected to industrial-grade data loggers. That allows us to record the temperature inside the coffee grounds while brewing is underway.
We measure the temperature inside the brewing chamber of every coffee maker we review.
After brewing coffee, we take sample readings of the brewed coffee liquid with a optical refractometer. Since we factor in the amount of water and freshly ground coffee used, that data allows us to calculate the Total Dissolved Solids percentage of each brew. From there we get to the take percentage. The ideal range is generally thought 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 often weak or sour. To be specific, we do identical test runs at least three times to understand the average results.
