During our first evaluation process, our reviewers began by hand-washing and drying all removable parts and accessories. For most espresso machines, that includes the filter basket, metal portafilter inserts, water tank and so on. Then it was time to grind the coffee beans to a fine, consistent grind, which is critical for proper espresso brewing.
Next, it’s time to pull shots. We start with the suggested method outlined in a given machine’s product manual. Usually, that covers the amount of coffee grounds expected per shot, along with any guidelines regarding coarseness level. Likewise, we follow tamping instructions (light, medium or hard tamp) if the manual provides them.
We make sure to record the weight of the grounds used, plus the weight of the espresso for each shot pulled. This data, along with readings from a portable refractometer, allows us to calculate two important percentages: total dissolved solids and extraction percentage.
Just as for any coffee brew, the ideal extraction percentage for espresso is a range between 18% and 22%. This yields a balanced cup, assuming you perform an even and efficient extraction of coffee compounds from your grounds (both flavor and caffeine).
If you over-extract, you run the risk of leaching out unpleasant flavors (bitterness) after the good. On the opposite end of the scale, under-extracted brews tend to have undeveloped flavors. Lacking sugars and other caramelized organic chemicals, these shots will taste sour, weak and watery.
Unlike a cup of drip coffee, barista-quality espresso should be concentrated. Excellent drip typically has a TDS percentage of 1.3% or 1.4%, great espresso has a much higher percentage. The Breville Barista Express, for example, produced shots with TDS percentages as high as 12.4%.
The shots we pulled were balanced, with an extraction of 18.6%. The test coffee beans I use are the same variety I employ for standard coffee makers — Costco Kirkland Colombian. It’s a medium-dark roast suitable for brewing espresso as well.
Lastly, we try our hand at milk frothing with each espresso machine equipped with a steam wand. I record the overall experience with the steam wand, whether the process is a snap, a tricky chore or somewhere in between.
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