Poor Results from Coffee Factors

  • The Roast – The darker the roast, the glossier the surface of the beans will be. This means that the oils have been roasted to the surface and these will need to be used fairly quickly to prevent evaporation of the oils. Letting glossy beans wait in unsealed containers will dry them out and, when brewed, will produce a result that is lacking in the normal, rich créma.
  • Freshness of Grind – Pre-ground coffee will also allow more of the oils to evaporate before they can be used. The results of using pre-ground espresso that has a roasted on date that is very much in the past is that the espresso will be lacking the full créma, may be less aromatic, and may come out watery, thin. Keeping pre-ground espresso in an air-tight container and making sure that it is finely ground to provide the most surface area for the water to pull out the remaining oils can help with these issues for pre-ground espresso.
  • Coarseness – The grind of the coffee is very important. Twenty coffee beans ground on a very coarse setting will take up more room then twenty beans ground on an incredibly fine setting. If darker, oilier beans are used, the grind will need to be fine to make sure that the highest amount of oils are utilized during extraction. Milder roasts will not need to be as fine in order to get the same quantities of oil and flavor intensity. If the beans are older, the grind, again, will need to be a bit finer in order to make sure the most oils possible are extracted. However, too fine of a grind can cause the water to only drip out during extraction, making the espresso taste a bit burnt. Too coarse and the water will flow out too quickly, leaving the espresso weak.
  • Tamping Depth – The tamping of the grounds is the next coffee factor. Depending on the coarseness of the grind being used, more or less coffee may need to be added to the portafilter. A general guide is that, once tamped, the coffee grounds should be about 1/8th of an inch below the top edge of the portafilter. For a visual, that’s about this long _. It should be roughly this low to allow the coffee to be close enough to where the water comes out so that a good pressure seal can be created easily but far enough away that the grounds are not pressing up into the shower head that the water is coming out of, effectively blocking them. The tamp of the grounds should force the grounds down that 1/8th of an inch below the top edge of the portafilter. If the coffee is pressed too far down, the water will just flow through it quickly. If it is too close to the shower head, it will barely drip out.
  • Tamping Pressure – Tamping pressure is also a factor in the extraction. Packing down the grounds as hard as possible will not allow enough room for the water to flow through. Not packing down the grounds tight enough will produce weak results as the water will flow through too quickly. The general idea is to put around 30 lbs of pressure on the grounds when tamping. Getting the entire section of ground coffee compressed with just a tamp is impossible, however, 30 lbs of pressure will compact the upper portion enough to force the water to around 9 bars of pressure to get the fluid through the grounds. While the upper portion provides the initial resistance to make good créma, it’s the slightly looser grounds at the bottom that keep the flavor pressure up. Once water hits the grounds, they expand and while the upper portion is the initial resistance, once the bottom portion expands with moisture, it, too, provides similar resistance and pressure. 30 lbs will compact the upper section of grounds to make the rich aromatic créma generally sought.
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