By any measure, coffee is the most complex beverage in the world. Comprised of 98-99% water, the entire science of coffee comes down to the absorption and extraction of solids and oils found within the beans. “There are approximately 1, 500 aromatic and flavor compounds in coffee—for comparison’s sake, wine has about 200″, says Erin Molnar, manager of Rising Star Coffee, relating that water essentially must absorb those flavors and minerals are responsible for taking up coffee’s essence. This rate of absorption, and the solids and oils which are extracted are determined by a whole host of variables:
Variable Effect Bean origin Not all beans have the same chemical composition. Bean roast The chemical composition of the coffee bean changes throughout the roasting process. Size of coffee grindings A consistent particle size is important, as the higher the surface area, the faster the extraction. Dry mass of coffee grindings A different extraction composition. Temperature of extraction The temperature dictates both the rate and composition of the extraction. Pressure of extraction Has a similar effect as temperature. Time of extraction Increasing extraction time allows for greater extraction. The water The variable is less obvious, but it is clear that the chemical composition of water (i.e. dissolved ions) play a very important role.
Source: Schrödinger’s water for perfect cup of Coffee, Chemistry World Blog 6/11/2014
The least understood, but likely most important is the water. Yes. If you are spending $17 per 12 oz bag of coffee and not spending the time and effort to perfect your water, you may be missing out on many of the hidden flavors still locked in the beans. Water is a canvas for these flavors. The mineral composition and chemistry of the water is as much a determining factor to what you are tasting as the beans themselves.
So, how do you perfect your water? There are as many opinions as there are roasters. The SCAA has released general guidance to improve the “overall” flavor of extracted coffee
Characteristic Target Acceptable Range Odor1 Clean / Fresh, Odor free Color2 Clear color Total Chlorine 0 mg/L TDS3 150 mg/L 75-250 mg/L Calcium Hardness 4 grains or 68 mg/L 1-5 grains or 17 mg/L – 85 mg/L Total Alkalinity 40 mg/L At or near 40 mg/L pH 7.0 6.5 to 7.5 Sodium 10 mg/L At or near 10 mg/L
- Odor is based on sensory olfactory determination
- Color is based on sensory visual determination
- TDS measured based on a 4-4-2 conversion
