Roasting and freshness

All questions in this silo, listed with their quick answer. Click for the full entry. — 35 questions.

• What is Agtron in coffee roasting?

  Agtron is a colorimetric measurement system used in coffee roasting to objectively quantify the roast level. It assigns a numerical score based on the near-infrared reflectance of ground coffee: the h

• Why should you avoid supermarket coffee for quality?

  Four cumulative reasons: no roast date (only a 12-18 month best-before, so coffee is often several months old), standardized fast-dark industrial roasting that hides defects, untraced origins (anonymo

• What is baked coffee in roasting?

  A baked coffee is a roasting defect caused by an insufficient Rate of Rise (RoR) during the Maillard phase — the temperature curve stays flat or rises too slowly for too long, producing a coffee that

• What is caramelization during roasting?

  Caramelisation is the thermal breakdown of sugars — mostly sucrose, glucose and fructose — which starts around 160 °C, intensifies past 190 °C and peaks in the development phase after first crack. It

• Why does coffee need to degas after roasting?

  During roasting, a bean accumulates 2 to 4 ml of CO2 per gram, trapped inside its cellular structure. That gas leaves the bean gradually afterwards — quickly in the first 24-72 hours, then slowly over

• How long does coffee stay fresh after roasting?

  The optimal tasting window of a specialty coffee sits between 7 and 45 days after roasting, peaking between 10 and 28 days depending on method and roast degree. Beyond 45-60 days the coffee is not uns

• What is a dark roast?

  A dark roast enters second crack or goes beyond it, bean temp between 225 and 245 °C, Agtron 35-60, with oils clearly visible on the bean surface. Sub-grades include Full City+, French (late 2C), and

• What is Development Time Ratio in roasting?

  Development Time Ratio (DTR) is the percentage of total roast time spent after first crack. It is calculated by dividing the time elapsed between first crack and the end of the roast by total roast ti

• Drum vs air roaster: what's the difference?

  A drum roaster heats beans through conduction and convection via a rotating metal cylinder that is directly heated, while a fluid bed (air roaster) suspends and agitates beans in a pulsed stream of ho

• What is an espresso blend and how is it roasted?

  An espresso blend is an assembly of several green coffee origins, designed to produce in espresso a balanced, reproducible and complementary profile — where a single origin might lack body or be too a

• What is the first crack in roasting?

  First crack ('1C') is the audible popping that occurs around 196-205 °C bean temperature. It is caused by the bean's cellular structure rupturing under the combined pressure of residual steam and CO2

• What is the difference between flavor development and body development in coffee roasting?

  In specialty coffee roasting, 'flavor development' refers to the construction of complex aromatics (acidity, fruitiness, florals) primarily through Maillard reactions, while 'body development' refers

• Should you freeze coffee beans?

  Freezing coffee beans is a valid and effective storage method when done correctly — that is, in airtight single-use portions, starting from fresh beans, without thawing and refreezing. It can preserve

• Difference between French and Italian roast?

  French roast and Italian roast are the two darkest levels on the standard roasting scale. French roast (approximately Agtron 25–35) sits just past second crack — beans are dark, slightly oily and pres

• What is ideal charge temperature in roasting?

  Charge temperature is the temperature of the roaster drum at the moment green beans are loaded. It is a critical parameter that determines the intensity of the initial thermal shock experienced by the

• Why are Italian espresso roasts darker?

  Italian espresso is a 9-bar extraction in 25-30 seconds: a violent regime that demands coffee whose flavours still read through pressure and heat. A dark roast (drop 225-245 °C, DTR 28-35 %+, surface

• Difference between light, medium and dark roast?

  Three roast families are defined by drop temperature and stop timing: light (Cinnamon/City, 205-215 °C, just after first crack), medium (City+/Full City, 215-224 °C, end of development), and dark (Fre

• What is a light roast coffee?

  A light roast ends 60 to 120 seconds past first crack, at a bean temperature of 205-215 °C, with a whole-bean Agtron reading between 80 and 95. The surface stays dry and the colour sits around pale ha

• What is the Maillard reaction in roasting?

  The Maillard reaction is a non-enzymatic browning triggered roughly between 140 and 200 °C, in which free amino acids in the bean react with reducing sugars to form brown melanoidins and several hundr

• How to match roast level with brewing method?

  Choosing a coffee by roast level should be guided by the intended brewing method: light to medium roasts shine in filter methods (V60, Chemex, Aeropress, French press) that reveal their acidity and ar

• What is a medium roast?

  A medium roast extends development for 2 to 3 minutes past first crack, reaching 215-224 °C bean temp (City+ to Full City), Agtron 65-80, with no visible surface oil. It is the sweet spot between pres

• Why do some beans show oil on surface?

  Oil on the surface of roasted coffee beans consists of lipids — primarily coffee oils (cafestol, kahweol, linoleic acid) — that migrate from the heart of the bean to the surface during dark or very da

• Why are one-way valve bags important?

  One-way valve packaging is a crucial innovation for the preservation of roasted coffee: it allows the CO₂ produced by freshly roasted coffee to escape without letting outside oxygen enter the bag. Wit

• What is post-roast blending?

  Post-roast blending is the practice of assembling coffees that have been roasted separately to distinct profiles and then mixed after roasting. Unlike pre-roast blending (where origins are combined be

• What is rancid coffee and how to avoid it?

  Rancid coffee is coffee whose lipids (oils) have undergone advanced oxidation, releasing aldehydes and ketones with smells of wet cardboard, old oil, rancid butter or wax. It is the main defect of cof

• What is Rate of Rise (RoR) in coffee roasting?

  Rate of Rise (RoR) is the speed at which bean temperature increases during roasting, expressed in degrees per minute. It is one of the most closely monitored parameters in precision roasting, allowing

• How to recognize freshly roasted coffee?

  Four tells: an explicit roast date (ideally < 21 days), a one-way valve bag that swells slightly or exhales softly on opening, a powerful complex aroma on first sniff (floral, fruity, sweet), and a st

• What is a roast curve?

  A roast curve (or roast profile) is a graphic representation of how bean temperature evolves over time during roasting. It is the 'fingerprint' of a roast: analysing it allows the roaster to reproduce

• Difference between Scandinavian and Italian roasting?

  Scandinavian (Nordic) roasting is light, fast and filter-oriented, dropping beans at 205-212 °C, Agtron 80-95, with a floral-fruity-bright profile. Traditional Italian roasting is dark, pushed into se

• What is the second crack in roasting?

  Second crack is a drier, metallic snap that occurs around 224-230 °C bean temp, typically 2 to 4 minutes after first crack. It signals that the cell-wall cellulose is yielding to advanced pyrolysis, r

• Why is specialty coffee often lightly roasted?

  Specialty coffee (SCA score ≥ 80) is selected for its intrinsic aromatic profile, tied to origin, variety and process. The roaster's job is to reveal that profile, not to cover it with roast flavours.

• How to store coffee beans fresh?

  To keep beans fresh: airtight opaque container, at room temperature (18-22 °C), away from oxygen, UV light, humidity and heat. Never the fridge (humidity plus odour absorption). For storage beyond a m

• What is underdeveloped coffee in roasting?

  An underdeveloped coffee is one whose development phase during roasting (after first crack) was too short or insufficiently hot to allow full conversion of sugars and degradation of compounds responsi

• What is coffee roasting?

  Roasting is the controlled cooking of green coffee in a drum or fluid-bed roaster, at temperatures between roughly 180 °C and 230 °C, for 8 to 18 minutes. It turns a hard, grassy, almost odourless see

• What is yellowing in coffee roasting?

  Yellowing is the first visible phase of the coffee roasting process: green or bluish beans gradually turn straw yellow. This stage corresponds to the evaporation of residual moisture inside the bean,

← Back to all FAQs (s5: 35 questions)