Coffee Buying Guide
Since espresso extraction is a much more concentrated brewing method than other coffee brewing methods, the quality of the bean is very important. Espresso concentrates and amplifies the inherent flavors of the beans. Simply put, if the beans being used are poor quality, then the resulting extraction will also be poor quality. Just like any other form of cooking, using quality ingredients is important for getting the best results. When selecting a bean you will want to anticipate what flavor profile you would like and what equipment you will be brewing on.
Selecting the right bean for the right beverage is the first step to pulling a great shot, and often overlooked. For simplicity, let’s break down the innumerable varieties of coffee into three categories: light, medium, and dark roasts.
Roasting changes the flavor of the beans by heating the beans. This causes some of the chemical compounds to denature, some of them to burn off or be removed by steam, and increases the carbon content of the bean. How much of the original flavor of the coffee is left depends on how much the bean is roasted. Because of how much the heating can change the flavor of the coffee it is an important factor to consider.
- Light Roast
- A light roast is typically picked when trying to emphasize the natural flavors of a coffee. The flavor compounds in the bean have not been greatly affected at this point.
- Medium Roast
- Medium roasted beans take on more carbon content, and the flavor compounds will begin to be roasted out of the bean through steam, or burned off from oils that are pushed to the surface of the bean. For the most part though the flavors will still be fairly intact, but will start to be masked by the caramelization of the sugars in the bean.
- Dark Roast
- Dark roasts modify the flavor content of the bean the most. At this point the sugars have almost completely caramelized, turning into carbon. This roasts will have strong bitter, smoky, and burned notes. These beans can be problematic in burr grinders and super-automatic machines, because they have such high surface oil content that they clog the grinding mechanisms of these machines. Dark roasts are frequently used for beans with defects, or poor quality beans. Since this roasting process removes most of the natural flavor of the beans, undesired flavors are easily masked. Caution should be used when purchasing darkly roasted beans - make sure you are getting a quality product.
Robusta and Arabica
Robusta and Arabica are two species of the Coffea genus, and comprise most of the modern coffee market. Robustas produce a lot of crema, so high quality robustas are frequently used in espresso blends. Robustas do not have many varietals. Arabica on the other hand comes in a large variety of subspecies, commonly referred to as varietals or cultivars. Arabica has such a wide range of cultivars because it has two additional chromosomes. Because of this wide range of subspecies there will be a broad range in quality and flavor. Arabica beans are cultivated at higher altitudes while Robusta beans are grown at lower altitudes. Typically, the roaster will mix both coffees together to create a coffee blend that works well with different brewing methods.
Preground Vs. Whole Bean
Coffees are sold as whole bean or preground. If you have the proper equipment to grind whole bean coffee, this will always be the better option. Purchasing whole beans is better for several reasons. The most important factor is that coffee beans are like any other perishable food item - the quality of the bean goes down as it ages. By keeping the bean whole the rate of decay is much slower. This is because whole beans have much less surface area. When a bean is ground, the greater surface area leads to more rapid oxidation like you might see in sliced apples.
Also important is that the coffee is already ground for you. You have no control over the grind size, so the coffee may not be ground appropriately for the brewing equipment being used. Correct grind size is essential for good tasting coffee to extract at the correct rate. This is especially important for espresso extraction where even small changes in grind size will have a large effect on the rate of flow and resulting flavor of the coffee. When selecting a pre-ground coffee make sure that it is ground appropriately for the brew method it is being used for.