Blending coffee is a fine art that marries coffee beans from different origins to enhance the best qualities of each. Roasters choose coffees that complement each other with a delicate, matching, say, a coffee with high citrus acidity and light body to one with smooth chocolate notes and full, velvety mouth feel.
The blending of coffee is as old as coffee itself. Although the techniques vary, blending is used to optimize aroma, body and flavour: the goal is to make a coffee that is higher in cup quality than any of the ingredients individually, and, extremely important, maintain consistency in the final roasted product.
Each batch has it own personality in terms of taste, smell, body, chemical resilience to the hydrolytic action of water, etc., and blending can complete it and round it up or level it off.
Most espresso blends are based on high quality Brazil arabicas, some washed, some dry-processed. They often involve some African coffees for winey acidity or flowery fruitiness, or a high-grown Central American for a clean acidity. Some roasters add a little robusta to increase body.
Dry-processed coffees are responsible for the attractive ‘crema’ on the cup, among other mechanical factors in the extraction process Wet- processed Central Americans add positive aromatic qualities. Robustas are used in cheaper blends to increase body and produce more foam.
Besides subjective quality , blending also assists in maintaining objective quality, because the more complex a blend, the easier it is to maintain constant quality when some ingredients change.
With the exception of a few countries that pay considerable attention to quality, the majority of producer countries often add up small batches produced by different growers to form larger ones of a size required by roasters. Although care is taken so that only batches of equivalent quality are blended, the result of this deplorable practice is often a quality downgrading to a level below that of the best fractions.
Coffee history records a number of popular blends that are published and available for public consumption. Other ‘proprietary’ blends tend to
be closely guarded, with the information staying within a company structure. Proprietary or signature blend leads consumers to equate a particular coffee profile with a particular brand image. Blending requires the expert skill of knowing each ingredient coffee, having in mind a clear cup profile as the goal, and knowing how to achieve it.
Blending may be done before or after roasting. Blending before roasting is traditionally used by retail and institutional roasters. In this method coffees with similar characteristics are combined and roasted to the same development. Generally, professional in-house ‘cuppers’ evaluate the results of the blend, adjusting components if necessary to satisfy taste requirements and standards.
Advantage: Consistency of product.
Disadvantage: Inability to optimize the character of each coffee.
Blending after roasting is the method traditionally used by many specialty coffee roasters. The flavour profile development requires that each individual coffee used in the blend be roasted separately to optimize flavour. In other words, each coffee will have a different time and temperature setting. Consequently, the final roast development will be different for each coffee used in the blend. After roasting, each component of the blend is individually tasted (cupped), as is the final blend composition.
part of ESPRESSO COFFEE book by Andrea illy