Dalgona coffee

Aka whipped coffee 

Sugar as surfactant 

essentially lower the surface tension between a liquid and gas, the liquid being coffee and the gas being foam. Visually, a surfactant can be described to look like a tadpole. The head of the tadpole likes water (hydrophilic) and the tail does not like water (hydrophobic). Since the tail end does not like water, it will cling on to or “face” towards air and gas.

In this case, when we whip or froth coffee to form bubbles, the tail end of surfactants will face the bubbles. This essentially creates a barrier around each bubble, reducing the surface tension between the coffee and bubbles. The more we whip and froth the coffee, the more bubble barriers we create, which makes foam. 

Instant coffee:

Dalgona Coffee can be made with either instant espresso or instant coffee. The reason you can’t use regular ground coffee is because it requires a weaker coffee to water ratio (when brewed). The recipe for Dalgona requires a 1:1 ratio of instant coffee to hot water. Using this ratio creates a very concentrated and strong coffee. With less water, there’s more surface area from the coffee for the surfactants to create those bubble barriers and trap the air. 

Why sugar?

While the coffee makes the foam, the sugar creates the whipped effect. The surfactants in coffee are not enough to keep the bubbles from maintaining their shape. If you foam your coffee without sugar, you’ll notice that after a few minutes the bubbles will either rise up from your coffee or merge together, and collapse. Coffee contains small amounts of oil that can enter those surfactant bubble layers and break down those bubbles. 

How about Americano + ice cube then blend?

Iced americano 

Reference:

Waka coffee 

Arif

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