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. .)

  • 1
    $\begingroup$ Peanut butter has peanut oil. Oils kill any kind of milk or cream foam. Fancy chefs use a copper bowl to whip cream since copper can be cleaned of all oil. Plastic bowls retain an oil film and are not good for whipping cream. $\endgroup$
    – MaxW
    Nov 29, 2017 at 5:03
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    $\begingroup$ @MaxW, as I've gathered, oils are responsible for inhibiting protein-based foams like whipped Egg Whites that depend on their protein networks to retain air while whipped Cream is a fat-based foam, which means that oils can not be expected to have any appreciable affects against foaming (and they don't). Further, copper bowls are used for Egg Whites as copper interacts with the sulphur in the egg whites with the effect of stabilizing the foam to a further degree, cold, heavy metal bowls are preferred for whipping cream as they help in maintaining an optimally cold temperature. $\endgroup$
    – ditsuke
    Nov 29, 2017 at 7:32
  • $\begingroup$ You are right. I confused egg whites with milk/cream foams. Thank you for the correction. $\endgroup$
    – MaxW
    Nov 29, 2017 at 7:45


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