Coffee consumers in general are not the types to embrace changes in the taste of their daily cup, so roasters put special emphasis on keeping the flavour consistent.
Many of these companies also look to reduce costs by using cheaper varieties like Robusta which, skilfully blended, have an acceptable flavour for a large number of customers.
It is also usual practice to combine naturally roasted coffee with beans roasted with the addition of sugar ('torrefacto'). During the roasting process the 'torrefacto' coffee becomes bitter and is suitable for drinking with milk, which is how the majority of coffee drinkers take theirs.
These are the reasons why different types of grain are often combined.
The blends which are most in demand are those that combine different types of Arabica coffee.
Each variety of bean has its own organoleptic characteristics; the most important are aroma, acidity, fruitiness, sweetness, body and bitterness. All these attributes cleverly combined will provide a complex and balanced cup of coffee.
Many of the best blends have a base of Brazilian or Indonesian coffees, famous for their pronounced body and chocolate notes.
Other beans from Central and South America provide fruity and floral aromas and the African coffees can enrich the blend by adding spicy and citric notes.
To make the perfect blend the master toaster, helped by a taster, has to get a harmonious balance sometimes achieving results typical of an alchemist.