Index of terms
List of some of the terms we have used here and on social media:
Moisture Content (%) – Moisture content in a coffee bean is the measurement of the percentage of water in the coffee bean. Typical moisture meters use capacitance to measure the moisture content in a bean by the ability of the coffee bean to store energy. Most specialty should be between 9-12.5% (M.Strumpf – DR Wakefield)
Water Activity (aw) - Water activity in a coffee bean is the measurement of the state of energy of water in the bean. Handheld and bench top water activity meters often use thin film capacitors to measure the water activity. These capacitors measure the ability to store energy in a closed container of coffee. The more water is present in the air above the coffee in the container, the lower the capacitance, and the higher the water activity. Conversely, the less water is present, the higher the capacitance, and the lower the water activity. (M.Strumpf – DR Wakefield)
Bean Density – Mass/Volume, a good sign of quality coffee, also lets me know how much heat I’ll need to apply to roast.
Roast Profile – A graphical representation of what’s happening while the beans are in your roaster, tracking temperature, airflow, time, gas, drum speed etc.
Roast time – Total time from the beans entering the roaster and coming out into the cooling tray (I’ve done roasts from 7-18 minutes, all about context*)
RoR (Rate of Rise) – A graphical representation of how fast/slow a roast is going, essentially the acceleration of the roast, this I so important to create good heat transfer and even, developed roasts.
Drying Phase – The start of the roast, after turning point this is the first stage where heat transfer occurs, higher RoR to start the development of the beans.
Soak – A term used for low or no gas/power at the start of the roast, or turning point (beginning of the roast) Used sometimes to lengthen a roast but ensuring a more gentle start to heat application.
Mailliard Reaction – Or colour change, this I the the same chemical reaction as meat browning that happens during cooking, Maillard reactions can produce hundreds of different flavour compounds depending on the chemical constituents in the beans the temperature, the total roast time, and the presence of air or speed of air. These compounds, in turn, often break down to form yet more flavour compounds
First Crack – An audible cracking, or popping noise that comes from the beans, it is where the beans have been given so much energy that the gases and moisture inside express to the surface, the beans grow in size and this is start of the development time in a roast.
Second Crack – Comes after 1st crack, associated with far darker roasts, this is when the oils inside the bean migrate to the outside and the cellulose structure of the bean starts to degrade.
DTR (Development time Ratio) - DTR is calculated as time from First Crack to the end of the roast, as a percentage of total roast time, can be an indicator for QC and balanced roast profiles.
Agtron Reading – Or Roast Colour reading The Agtron uses near infrared light to analyse the colour of ground or whole bean coffee. It then outputs an easy-to-read number that represents the degree of roast. The lower the number, the darker the roast, most of the coffees I roast are between 65-85 agtron, for a reference, a very dark roast would be >50 agtron.
Freshness: Freshly roasted coffee necessarily undergoes a period of aging that allows it to degas. Gases from the roasting process eventually exit the pores of the bean, making it more permeable. Coffee that has not degassed sufficiently will be less permeable and difficult to extract.
Water type: Water quality varies greatly depending on geographical origin, local water treatment, and in-house filtration. Calcium, alkalinity, pH, and sodium—as well as total dissolved solids (TDS)—impact how soluble compounds are extracted from coffee, so it’s important to know what’s in your brewing water.
Brew ratio: The ratio of coffee grounds to water; or, how much coffee is used for a given quantity of water. This may be expressed in units of either grams or ounces. A 1:16 coffee-to-water ratio is commonly recommended as a starting point.
Grind size: Grind size and burr setting directly correspond to surface area. Generally, increased surface area means increased extraction potential. A whole bean has very little surface area compared to a bean that is broken up, which is why we brew with ground coffee. The smaller, or finer, the grind size, the more surface area there is and the easier it is for water to extract flavor. The opposite is true for larger, or coarser, grind sizes. In addition to drastically affecting the coffee’s solubility, grind size also affects flow rate (think water flowing through boulders versus sand), which will in turn affect water contact time.
Temperature: Hot water extracts coffee flavor faster than cold water. That’s why cold brewing takes hours while hot brewing takes minutes. However, too-hot water can burn coffee and lead to over extraction. The industry generally considers the ideal brewing temperature to be between 195 and 205 degrees Fahrenheit. Temperature stability throughout the length of the brew cycle is desirable for replicable results. Just as baking foods at different temperatures will result in drastically different results, different brew temperatures will extract coffee differently.
Contact time: The length of time water and grounds are interacting. Too short = under extracted; too long = over extracted.
Bloom: The initial wetting of the grounds. This phase prepares particles for extraction of solubles, both by helping to release CO2, and by allowing subsequently added water to move more freely through the bed of grounds (an even pre-wetting should result in a more even extraction).
Strength/(TDS): TDS refers to the solids dissolved in the cup, which does not include crema or oils formed on the surface. This is measured with a refractometer. TDS translates to concentration of dissolved coffee solids in the cup and is described in terms of strength. The higher the concentration of TDS, the stronger the cup. The lower the concentration of TDS the weaker the cup. In practice, strength is determined by how the coffee feels in your mouth. Strong cups feel thick or heavy while weak cups feel thin or watery.
Agitation: This is the word we use for creating turbulence in the coffee (with a spoon or with the water stream from the kettle). Agitation directly relates to the rate of extraction, so this variable should be kept consistent from brew to brew.
Flow rate: the rate at which water flows through coffee.