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LAS estate-copertina def.indd 1 24/06/11 10:16

L’ASSAGGIO 33 - PRIMAVERA 2011 9

A fundamental phase in the work of the coffee roaster in creating a per-fect product is the choice of green coffee. Here are some guidelines for choosing the best raw material.

The Selection of Green Coffee

The Qualities of Green CoffeeRegardless of whether coffee is processed to create a blend or destined to be consumed as a single origin coffee, the selection of green cof-fee is fundamentally important for the final re-sult. In short, the quality of coffee is positively linked to:• the homogeneity of bean size;• the homogeneity of the colour of the beans,

both compared to each other and across the surface of a single bean;

• carbohydrate and, above all, arabinose con-tent, which indicates maturity levels;

• fat content;• amount of certain aliphatic acids.On the other hand, quality is negatively linked to:• chlorogenic acid content;• caffeine content;• compounds which identify anomalies in the

production cycle (trichloroanisole, geosmin, etc.)

Most Common DefectsSome defects are visible to the eye, others are not, but one thing is certain: sometimes just a few defective beans can ruin an entire batch of good coffee. That is why selection is important and why investments made in equipment or in

the selection process are normally repaid well with regard to quality.

Black bean (preto)

• Physical evidence: totally or partially black bean.

• Point in chain: in the field, due to attack by fungi such as Colletotrichum coffeanum, im-mature beans attacked by yeasts, or imma-ture beans that have not been well processed.

• Chemical evidence: proteins and lipids in the surface cells are degraded.

• Sensory evidence: astringent to the touch, vegetable and/or wild scent.

Immature bean (quaker)

• Physical evidence: wrinkled, grey-green sur-face, in some cases tending towards black.

• Point in chain: harvest.• Chemical evidence: sucrose is absent or al-

most absent, while arabinose, a sign of imma-turity, is still present. Chlorogenic acids may exceed 15%, while the content of lipids is low.

• Sensory evidence: higher astringency cou-pled with hard acidity, vegetable odour simi-lar to peas and chicory.

Fermented bean (ardido)

• Physical evidence: bean is light on the out-side and dark brown on the inside.

COFFEESELECTION

10 L’ASSAGGIO 33 - PRIMAVERA 2011

• Point in chain: processing of green coffee.• Chemical evidence: attack by moulds Asper-

gillus and Eurotia in beans that are still in the dried cherry.

• Sensory evidence: odour of fermentation.

Stinker bean

• Physical evidence: brown-coloured bean, from light to dark brown.

• Point in chain: processing of green coffee.• Chemical evidence: anomalous fermenta-

tion with formation of lactic and propionic acids and their esters, disulphide and di-methyl sulphide, which can reach values of 2 and 3 times the norm, respectively.

• Sensory evidence: rotten and fetid odour.

Mouldy bean

• Physical evidence: appearance of mould.• Point in chain: processing of green coffee.• Chemical evidence: formation of com-

pounds typical of mycotic attack, including geosmin.

• Sensory evidence: mouldy odour.

Earthy bean

• Physical evidence: brown to black colouring.• Point in chain: processing of green coffee

with drying on humid land.• Chemical evidence: high levels of methyliso-

borneol.• Sensory evidence: earthy odour.

Waxy bean

• Physical evidence: translucent yellow-green or reddish coloured surface.

• Point in chain: processing of green coffee with attack by microorganisms.

• Chemical evidence: sulphide compounds.• Sensory evidence: rotten smell.

Peasy bean

• Physical evidence: none.• Point in chain: in the field, due to attack

from bacteria from the enterobacteriaceae family.

• Chemical evidence: the 2-isopropyl-3-me-thoxypyrazine can reach values of 2,500 ppb (threshold value in water 0.1 ppb).

• Sensory evidence: vegetable sensation of fresh peas.

Whitish bean (biancone)

• Physical evidence: decoloured surface.

• Point in chain: processing of green coffee with fermentation caused by streptococci.

• Chemical evidence: metabolites typical of bacterial attacks.

• Sensory evidence: reduction in aromatic in-tensity and increased bitterness.

Riato bean

• Physical evidence: none.• Point in chain: in the field or during the

treatment of green coffee due to microor-ganism attacks.

• Chemical evidence: presence of 2,4,6-tri-chloroanisole.

• Sensory evidence: iodised, carbolic, medici-nal odour.

Worm-eaten bean

• Physical evidence: some small holes.• Point in chain: in the field due to attacks by

Hypothenemus hampei.• Sensory evidence: increased bitterness.

Dark-brown bean

• Physical evidence: colour of monk’s black cassock.

• Point in chain: in the field due to attack by chemicals on the immature cherry.

• Chemical evidence: increased acidity.• Sensory evidence: a strange fruity aroma ac-

companied by aggressive acidity.

Deformed bean

• Physical evidence: unusual bean form.• Point in chain: in the field due to growth

defect.• Chemical evidence: low acidity.• Sensory evidence: aroma is not intense and

there is little acidity.

Dark green bean

• Physical evidence: dark green coloured bean.• Point in chain: harvesting of immature

beans and drying at high temperatures.• Chemical evidence: sulphide compounds.• Sensory evidence: rotten fish smell and high

astringency.

Cut bean

• Physical evidence: cut bean.• Point in chain: processing of green coffee

with incorrect calibration of cutter.• Chemical evidence: sulphide compounds.• Sensory evidences: fermented odour.

SELECTIONCOFFEE