DETERMINING SPECIALTY COFFEE QUALITY. PHYSICAL ANALYSIS AND GREEN COFFEE DEFECT GUIDE





In order to define coffee quality, each operator in the value chain has her own parameters. The degree of compliance with the latter establishes the different classifications we usually find in the green coffee trade. 


Quality control is an aspect taken into account in each and every step of the production chain. This not only ensures pure sensory quality, but also adds greater value to the product, each time that the quality control process takes place.

When defining the quality of a specialty coffee lot, we must consider both the visual aspect (physical quality) and the cup profile (sensory quality) of the sample. For those purposes, there is a standard protocol used by professional cuppers, which helps them in classifying coffee in qualitative terms.

However, in order to produce a specialty coffee, a lot of work comes before doing the physical and sensory analyses of a green coffee sample.


Quality at origin: growing, processing, sorting


Producing specialty coffee starts on the farm, when the producer decides where she’ll plant her coffee trees, which variety will be grown and how she will manage the crop (nutrients, protection against pests and diseases, weeding, shade, pruning, harvesting) in order to obtain high quality coffee beans.

Later on, pickers are the ones responsible for quality control. They select cherries that are fully mature in order to ensure that the beans contain the best possible aromas and flavours.

Choosing the most apropriate processing and drying methods is the next key aspect in quality control, followed by the sorting of fresh cherry (natural method) or wet parchment (wet method) on the drying tables.


Quality criteria for specialty green coffee


The Specialty Coffee Association (SCA), an international organisation that develops standards in coffee quality, has established a series of parameters, both in physical and sensory quality, which are used all around the world by Q-Graders.

The physical analysis of a green coffee sample* consists in evaluating the following aspects: 

Green coffee colour 
The colour of the green coffee sample may vary according to origin and to the processing method. Even though it’s not a proper quality indicator, the colour can give some information on the coffee.

Moisture content 
Bean moisture must be between 10 and 12% in order to avoid roasting problems (excessively dry beans) and microbiological problems (fungi grow in excessively moist beans).

Standard for measuring water activity in green coffee
Bean water activity should be below 0.70, in order to insure a long-term storage without major quality losses.

Bean size
Even though bean size does not have a direct influence on cup quality, it’s important to ensure that bean size is uniform throughout the lot in order to obtain the best results during the roasting process.

Defect count
SCA established a series of defects which we can usually find in a green coffee sample. For a coffee lot to be considered of specialty grade, in a sample of 350 g there shall be no primary defect and a maximum of 5 (five) secondary defects.

Primary defects are: full black, full sour, severe insect damage, fungus damage, dried cherry and foreign matter.

Secondary defects are: partial black, partial sour, slight insect damage, parchment, floater, immature, withered, broken/chipped/cut, shell and husk.




When counting the defects in a sample, we must consider a series of equivalences. For instance, a fully black bean represents one full primary defect, whereas in order to have one full primary defect due to severe insect damage, we’d have to find 5 beans with this defect. This is because different defects have different impact on cup quality.

Therefore, when we find a single bean with two or more defects, only the defect which has a higher impact on cup quality will be counted. 

 

Roasted coffee physical and sensory analyses
The following steps in the assessment of coffee quality are the visual inspection of a roasted sample and the sensory evaluation of 5 cups of brewed coffee.

According to the SCA’s cupping protocol, 100 grams of roasted coffee are taken to see if there are any quakers (lightly coloured beans). Specialty Grade must have 0 (zero) quakers and Q Grade may have 1-3. Any sample displaying 4 or more quakers in 100 grams will be classified as Commercial Grade.

Finally, sensory analysis consists in the evaluation of attributes, such as fragrance, aroma, flavour, acidity, body, among others, in order to establish a final score from 0 to 100. Coffee samples that cup 80 points or above will be considered specialty coffees.




Following this classification system helps us in finding different categories in the coffee trade. This way, if every coffee finds an appropriate buyer, a higher proportion of the harvest will be sold, thus fostering a more sustainable trade.

It’s important to use common sense when considering the defects found in a coffee sample, keeping in mind all the hard work done at origin. Manual selection is still the most common method for sorting out defects and is usually carried by women. Selecting beans manually in order to meet a green coffee physical standard takes a tremendous amount of work.

Xorxios’ philosophy is based on the respect towards the effort of each and every operator in the coffee value chain. To us, it’s the only way to obtain a high quality product and to ensure that the trade is sustainable and respectful

 

 

* Source: Specialty Coffee Association. SCA Handbook Series: The Washed Arabica Green Coffee Defect Guide.



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