Slow Roast OR No Roast?

Oct 26, 2012




Perhaps more important than recipe or blend or quality of original coffee is degree roast.


A bit of a ‘Cinderella’ in the coffee trade, roast can create havoc and reduce grown men to blubbering wrecks, as those ‘in the know’ argue over the precise roast colour which should be attained for a specific blend, or a particular original coffee.

Not as sexy as recipe or as exotic as country of origin, roast is often overlooked by the consumer…but of all elements it is the single most important key to the beverage experience!

Recent ‘slow roast’ marketing efforts now seem to be re considering the role of roast colour in the production of a quality bean. Inevitably, this has a commercial focus driving prices higher…but it is also a most important facet of the coffee production process.

Degree of roast is crucial because the cooking process determines the way in which the flavour of the beans develops.

Cooking or roasting results are completely dependent upon  the time and temperature at which the beans are roasted and the levels at which the volatile fractions of roasted coffee –

Pyrroles / Ketones / Pyrazines/  Furans/ Phenoolics / Pyrdines / Alchols and Acids are released and relatively managed in the complex taste mix which is coffee.


The roasting process allows the organoleptic development of the coffee taste and enables pyrolitic reactions to take place which deliver the sensory qualities we know and love in coffee.

Simply put, lighter roasted coffee develops a brew, which is thin, acidic with less body and less aroma. Whereas, a darker roast delivers a heavier, heartier liquor with strong after notes, bitterness and a full and complex mouth experience…

The darker roast costs more, simply because more of the beans are lost in the burning process.

Typically, 17 > 20 % of the weight of beans put into the roaster is lost at the end of the process, bearing in mind green bean has a natural moisture content at c 13% and post roast will have a moisture level of zero, unless the master roaster elects to quench the roast, which can then add back up to 5% water to the mix.

Lighter roast coffees can have a yield loss of as little at 13% – the cost implications are clear.

Industrially, the degree of roast is measured by light reflectance and by visual inspection.

The value obtained via the light reflectance method is called the ‘chromatic value’ and is directly related to the final colour of the cooked beans…with the range typically covering a spectrum from-

 Light Roast

Chromatic Value 89

Roast Temperature 175 centigrade

Roasting time just short of 9 minutes


To a chromatic value of –


Dark Roast

Chromatic Value 64

Roast temperature 195 centigrade

Roasting time 11 minutes


Bearing in mind that as a minimum  beans can be high yield roasted for 90 seconds, or super slow roasted to 225 degrees for 20 minutes or more……It is a broad but beautiful church!

I find the following a useful ready reckoner-

George Steinert’s Degree of Roast/Temperature chart:

Degree of Roast Temp
Green Unroasted 75
Starting to pale 270
Early yellow 327
Yellow-Tan 345
Light Brown 370
Brown 393
1st Crack Begins 401
1st Crack Under Way 415
City Roast 426
City+ 435
Full City 446
Full City+ 454
Vienna (Light French) 465
Full French 474
Fully Carbonized 486
Immanent Fire 497

Those in the know and we here at Aromo understand great coffee is not about the marketing and Tom Cruise style cocktail goings on..its about great quality coffee…fresh water …good pressure and the time and skill to make and enjoy your espresso moment
Guru ( Andy Grelak) writes for Aromo Coffee – They are coffee experts focussed on providing convenient and tasty ways for the caffeine addict to take their medicine. Aromo supplies excellent ESE Coffee pods and superlative Senseo pods,  both of which offer the espresso and filter connoisseur  a no mess, no fuss,  super fresh and environmentally conscious method to make stunning coffee… the guys at Aromo also have a range of Dualit branded capsules which make a brilliant and economic alternative to nespresso capsules

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