I recently acquainted myself with the skill of whipping a mixture of sugar, fresh brewed/ hydrated instant coffee into a pale, fluffy, stiff and stable foam. This, as some might know, is known as Café Cubano or Whipped Coffee in some of parts of the world (gives you a foamy and light textured espresso).
The other day, I tried whipping the mixture, just with the addition of some peanut butter in the start (I had tried it with peanut butter before, but had added it at a later stage) and it failed to stiffen and hold up any air.
I am familiar with how whipping cream works: the mechanism is easily available to be read on several sources over the internet, but am unable to figure out the mechanism for the above mentioned mixture.
Also, I want to know why an impurity (peanut butter, as I've yet explored) inhibits the foaming process. What decides if a mixture can be whipped and how can it be predicted if a given mixture will foam?
All insights are welcome. .)