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ESTATE 2011

Poste Italiane SpA - Spedizione in Abbonamento Postale - D.L. 353/2003 (com. L. 27/02/2004 n. 46) art. 1, comma 1 DCB Brescia

dall’analisi sensoriale al piacere

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SELECTION

COFFEE

The Selection of Green Coffee

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

The Qualities of Green Coffee Regardless of whether coffee is processed to create a blend or destined to be consumed as a single origin coffee, the selection of green coffee is fundamentally important for the final result. 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 content, 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 Defects Some 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, immature beans attacked by yeasts, or immature 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 surface, in some cases tending towards black. • Point in chain: harvest. • Chemical evidence: sucrose is absent or almost absent, while arabinose, a sign of immaturity, is still present. Chlorogenic acids may exceed 15%, while the content of lipids is low. • Sensory evidence: higher astringency coupled with hard acidity, vegetable odour similar to peas and chicory. Fermented bean (ardido) • Physical evidence: bean is light on the outside and dark brown on the inside.

L’ASSAGGIO 33 - PRIMAVERA 2011

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COFFEE

SELECTION

• Point in chain: processing of green coffee. • Chemical evidence: attack by moulds Aspergillus 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 fermentation with formation of lactic and propionic acids and their esters, disulphide and dimethyl 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 compounds 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 methylisoborneol. • 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-methoxypyrazine 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.

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L’ASSAGGIO 33 - PRIMAVERA 2011

• Point in chain: processing of green coffee with fermentation caused by streptococci. • Chemical evidence: metabolites typical of bacterial attacks. • Sensory evidence: reduction in aromatic intensity and increased bitterness. Riato bean • Physical evidence: none. • Point in chain: in the field or during the treatment of green coffee due to microorganism attacks. • Chemical evidence: presence of 2,4,6-trichloroanisole. • Sensory evidence: iodised, carbolic, medicinal 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 accompanied 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.

The Selection of Green Coffee  

A fundamental phase in the work of the coffee roaster in creating a perfect product is the choice of green coffee. Here are some guidelines...

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