Want to know how to make espresso? Let’s start by understanding the basics. Espresso is made by pressurizing very high temperature water through finely ground and compacted coffee beans. This process produces an almost syrupy beverage by extracting both solid and dissolved components. The crema is produced by emulsifying the oils in the ground coffee into a colloid which does not occur in other brewing methods, and is the essence of a beautiful cup of espresso! There is no universal standard process of how to make espresso, the act of making espresso is often termed “pulling” a shot. The essential operational parameters outlined by the Italian Espresso National Institute for making a “certified Italian espresso” are listed as bellow.
Are there any criteria to define a perfect espresso?
In fact, the sensory profile of the Certified Italian espresso has been determined through thousands of consumer tests carried out by the Italian Espresso National Institute. The combined results of consumer tests and laboratory tests have given the definition of high quality espresso are Color intensity@7, Texture@9, Olfactive intensity@9, Roast intensity@7, Body@9, Acid@7, Bitter@5, Astringent@2, Overall positive odors@9, Overall negative odors@2.
In order to meet perfect coffee quality requirements, it is undeniable that water plays a vital role, as the composition of a cup of coffee is around 98-99% water. The decisive factor affects the taste or aroma of coffee is reaction to water, with PH6-7 main acid of coffee bean during brewing process with hardness range from 17 ppm to 85ppm followed by SCAA standard. The instant brewing is a major factor for good taste of coffee.
Some researches state that coffee taste will be influenced by the Calcium, Magnesium, Sodium and Potassium in the water as they have a weak taste and their existence will eventually affect the final performance of a cup of coffee. To be more concise, some water contains high proportion of Potassium and Sodium, and the coffee made by that water will have a stronger salty taste. Moreover, general tap water contains chlorine and trace amounts of heavy metals, such as iron, which may destroy the flavor of coffee.
While there is another research from UK claims that compounds, minerals, in water are the crucial factor for proper extraction of coffee constituents. It is generally believed that hard water is not suitable for brewing coffee, but in fact it still depends on the compounds of the hard water. If the water contains too much bicarbonate, it will not be good for extraction. As in earlier research pointed out that the presence of bicarbonate will prolong the extraction time of coffee, however, high Magnesium ions increase the extraction of coffee constituents and contribute to the flavor of the coffee.
Among the three cations of sodium, magnesium and calcium, the interaction length distance of Magnesium ion is shortest compared to the above seven flavor coffee compounds, and a stronger binding energy which are both key dominating to generate extraction of coffee constituents.
A shorter extraction time decides crema & flavor or espresso!
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