Espresso is a method of brewing coffee that has fascinated coffee enthusiasts for decades. One of the most intriguing aspects of espresso is the crema, the foam that forms on the surface of a freshly brewed shot. The crema is not just for visual appeal, it plays an important role in the flavor and aroma of the coffee. Among the many characteristics of the crema, the tiger stripes are the most captivating.
The tiger stripes are formed by the emulsion of coffee oils and water vapour. The coffee oils are released by the high pressure of the espresso machine and are trapped by the water vapour. The emulsion creates a layer on the surface of the coffee that is rich in dissolved gases and lipids, which give the crema its characteristic colour, texture, and flavor.
The tiger stripes are a sign of a well-extracted shot and are considered to be a good indicator of the quality of the espresso. The stripes are created by the pressure of the machine and the distribution of the coffee grinds in the portafilter. The pressure of the machine must be high enough to extract the coffee oils, but not so high that it causes the coffee to become bitter. The distribution of the grinds must be uniform and tamped with the right pressure to ensure that the water flows through the coffee evenly, without creating channels that would cause the coffee to become overextracted.
The colour of the tiger stripes is also an indicator of the quality of the espresso. A light-coloured crema indicates that the coffee is under-extracted and that the pressure of the machine is too low. A dark-coloured crema indicates that the coffee is over-extracted and that the pressure of the machine is too high. The ideal colour for the crema is a rich, golden-brown colour that indicates a perfect balance of extraction and pressure.
In conclusion, the tiger stripes in espresso are not only a visual delight but also a sign of a well-extracted shot, and a good indicator of the quality of the espresso. The science behind the tiger stripes is a fascinating aspect of the art of espresso making. The next time you enjoy a cup of espresso, take a moment to appreciate the beauty of the tiger stripes and the work that went into creating them.