While tasting coffee, you should try to discern whether the flavour, body, acidity and aroma of the coffee is pleasant or unpleasant. Here are the criteria that most tasters use to judge coffee:
Acidity
Acidity is a desirable characteristic in coffee. It is the sensation of dryness that the coffee produces under the edges of your tongue and on the back of your palate. The role acidity plays in coffee is not unlike its role as related to the flavour of wine. It provides a sharp, bright, vibrant quality. Without sufficient acidity, the coffee will tend to taste flat. Acidity should not be confused with sourness, which is an unpleasant, negative flavour characteristic.
Aroma
Aroma is a sensation that is difficult to separate from flavour. Without our sense of smell, our only taste sensations would be: sweet, sour, salty, and bitter. The aroma contributes to the flavours we discern on our palates. Subtle nuances, such as "floral" or "winy" characteristics, are derived from the aroma of the brewed coffee.
Body
Body is the feeling that the coffee has in your mouth. It is the viscosity, heaviness, thickness, or richness that is perceived on the tongue. A good example of body would be that of the feeling of whole milk in your mouth, as compared to water. Your perception of the body of a coffee is related to the oils and solids extracted during brewing. Typically, Indonesian coffees will possess greater body than South and Central American coffees. If you are unsure of the level of body when comparing several coffees, try adding an equal amount of milk to each. Coffees with a heavier body will maintain more of their flavour when diluted.
Flavour
Flavour is the overall perception of the coffee in your mouth. Acidity, aroma, and body are all components of flavour. It is the balance and homogenization of these senses that create your overall perception of flavour.
The following are typical flavour characteristics:
General flavour characteristics:
Richness-refers to body and fullness
Complexity- the perception of multiple flavours
Balance- the satisfying presence of all the basic taste characteristics where no one over-powers another
Typical specific desirable flavour characteristics:
Bright, Dry, Sharp, or Snappy- [typical of Central American coffees]Caramelly -candy like or syrupy
Chocolaty- an aftertaste similar to unsweetened chocolate or vanilla
Delicate- a subtle flavour perceived on the tip of the tongue [typical of washed New Guinea Arabica]
Earthy- a soil-related characteristic [typical of Sumatran coffees]
Fragrant- an aromatic characteristic ranging from floral to spicy
Fruity- an aromatic characteristic reminiscent of berries or citrus
Mellow- a round, smooth taste, typically lacking acid
Nutty- an aftertaste similar to roasted nuts
Spicy- a flavour and aroma reminiscent of spices
Sweet- free of harshness
Wildness- a gamey flavour that is not usually considered favourable but is typical of Ethiopian coffees
Winy- an aftertaste reminiscent of well-matured wine [typical of Kenyan and Yemeni coffees]
Typical specific undesirable flavour characteristics:
Bitter- perceived on the back of the tongue, usually a result of over roasting
Bland- neutral in flavour
Carbony- burnt charcoaly overtones
Dead- see "flat"
Dirty- a mustiness reminiscent of eating dirt
Earthy- see "dirty"
Flat- lack of acidity, aroma, and aftertaste
Grassy- an aroma and flavour reminiscent of freshly cut lawn
Harsh- a caustic, clawing, raspy characteristic
Muddy- thick and dull
Musty- a slight stuffy or mouldy smell [not always a negative characteristic when in aged coffees]
Roily- a starchy texture similar to water which pasta has been cooked in.
Rough- a sensation on the tongue reminiscent of eating salt
Rubbery- an aroma and flavour reminiscent of burnt rubber [typically found only in dry-processed Robustas]
Soft- see "bland"
Sour- tart flavours reminiscent of unripe fruit
Thin- lacking acidity, typically a result of under brewing
Turpeny- turpentine-like in flavour
Watery- a lack of body or viscosity in the mouth
Wild- gamey characteristics