When you stop to think about it, a great cup of coffee is pretty amazing. At least a dozen factors have seriously influenced its flavor profile as it has traveled thousands of miles from seed to cup over a period of around 6 months. When considering the hours and hours of backbreaking work that went into growing and processing a specialty coffee, brewing it seems both relatively insignificant in relation to the overall process and incredibly important. The application of science to the taste of coffee and the technology that followed help us shoulder this responsibility and enables us to do some great coffee justice.
Coffee is one of the most complex beverages that humans consume. A cup of coffee can contain thousands of different chemicals that we can smell, taste, feel or see (wired.com). These chemicals are stored inside roasted coffee beans and grounds. It’s possible to pull almost 30% of the total weight a coffee bean out and into the cup. We call this process of pulling chemicals out of coffee grounds extraction. No good extraction is possible without great water filtration.
Water can be the diva that ruins your coffee production. Because brewed coffee is around 98.5% water, H2O significantly affects taste. The chemistry of water is very complex and its makeup can change seasonally and because of other factors such as local construction, variable sources and water bureau treatments, etc. Most water has many gases and minerals dissolved in it, not to mention floating bacteria and dirt. A simple charcoal filter helps remove dirt and odor but is not much help when it comes to mineral content. When water moves through the ground or in pipes, it extracts minerals from them the same way it pulls flavors from coffee. Some minerals, like iron, can produce bad coffee tastes or colors. Also, coffee just doesn’t taste as good when brewed with water that doesn’t have a fair amount of calcium dissolved in it. One measurement the SCAA uses to count the number of minerals dissolved in water is by measuring the total dissolved solids (TDS). The total dissolved solids are measured in parts dissolved solids, per million parts water (ppm). A TDS reading is partially a measure of whether a water is soft or hard. Water with a very high TDS reading (hard water) extracts coffee flavor less readily. The ideal range for TDS is between 125 and 175 ppm. The ideal range for calcium hardness is between 17 to 120 ppm. Iron, chlorine and chlorinates should not be present in a reading.
When evaluating the quality of brewed coffee it’s important to remember that personal taste is always the most important factor. With that being said, using tools to help measure strength and extraction can allow for more control over taste. Also, water filtration systems have wearable parts that must be replaced on a regular basis to ensure optimum performance. In general, carbon filters for in-line water filtration systems should be replaced every three to six months. Filters and membranes for reverse osmosis systems (e.g. Cirqua) should be changed once every year. Should you notice any debris, odor or off-flavors, or if you notice scale appearing on your equipment, replace these elements immediately.