Abstract:
Coffee foam is the frothy layer that forms above the liquid phase of espresso and instant coffee
beverages. While the carbon dioxide formed during roasting is responsible for crema formation in
espresso, gasification is the established foaming approach in instant coffee. The protein-like fractions and polysaccharides extracted from roasted coffee promote foamability and foam stability,
respectively. Crema of consolidated texture retains the volatile aromatic substances and prevents
the espresso from cooling too rapidly. Further, an inverse relationship has been observed between
foam persistence and volatility of aroma molecules above the cup. Gasified spray-dried instant coffee exhibited an accelerated delivery rate of hydrophobic aroma compounds. Thus, foam is the
signature of a high-quality cup of coffee. Despite its various functionalities, coffee foam is scarcely
investigated owing to its metastable nature. Only recently, the chemical, structural, and interfacial
rheology properties of the coffee foam have been looked at. The current study intends to review
the scientific knowledge acquired on coffee foam, thus far. The initial sections describe the general
attributes and functions of espresso and instant coffee foam. Further, the mechanisms of formation and stabilization of coffee foam are detailed, followed by the factors influencing the same.
The following discussions focus on the role of coffee foam in determining the sensory and aroma
release characteristics of the beverages. The scope for future research in this field of study is highlighted in the concluding section.
