Final answer:
Crema is the foam that forms on top of espresso. It is composed of oils, proteins, and sugars extracted from the coffee beans. Crema contributes to the flavor of espresso by adding a creamy texture, providing aromatic flavors, and preserving the volatile compounds.
Step-by-step explanation:
Crema is not a Viennese specialty, but rather a characteristic of Italian espresso. It is the golden-brown foam that forms on top of a shot of espresso. Crema is composed of various substances including oils, proteins, and sugars that are extracted from the coffee during the brewing process.
Crema contributes to the flavor of espresso in several ways. First, it adds a creamy texture to the drink, enhancing its mouthfeel. Additionally, the oils in the crema contain aromatic compounds that provide flavors like sweetness, fruitiness, or nuttiness to the espresso. Finally, the crema helps to preserve the volatile compounds in the espresso, protecting them from oxidation and ensuring a more flavorful cup.