[chiralSPO (OP)]

There is a phenomenon that I have witnessed many times over the years, but haven't actually seriously addressed at any point (yet).

I happen to like a little extra kick in my cocoa occasionally, and will brew a cup of strong black tea, to which I will add the dry ingredients for hot chocolate. Cocoa is quite hydrophobic, and when added to hot water will clump up on itself, only dispersing into the water after vigorous stirring. When added to the tea however, it appears to be much more easily wetted, and much less stirring is involved in preparing the hot chocolate. Question is why?

Perhaps some components of the tea reduce the surface tension of the water. Or maybe they act as detergents and decrease hydrophobicity... Is it a pH thing? What components would it be? Polyphenols are my best guess for any of the explanations (see compositions of tea: https://worldoftea.org/tea-chemistry/), but I am wondering if there are other possible explanations I have missed.

[jeffreyH]

The cocoa just doesn't get on with the tea and visa versa. So they try to get as far away from each other as possible.

[chiralSPO (OP)]

I see better mixing with tea than with water. If anything the cocoa seems to get on with tea much better than with water.

[jeffreyH]

The tannins are likely disrupting the dry surface of the cocoa powder.

[jeffreyH]

The tannins are likely disrupting the dry surface of the cocoa powder.

https://en.m.wikipedia.org/wiki/Tannin

[chiralSPO (OP)]

Yeah, tannins are a subclass of the polyphenols I implicated in my first post. It makes sense given their relatively high concentration in tea and ambiphilic nature (soluble in both organic and aqueous solvents). But is it an effect that the dissolved tannins have on the water, or do they act as surfactants and bind to the cocoa?

[petelamana]

I found this explanation for everyone.  It makes sense, but I'm not a chemist.  I hope it is correct.

In general, it can be stated that cocoa products are not as dissolvable or soluble as coffee products. This is of course due to the extraction or filtration process by which coffee is prepared. Coffee merely exists of water-soluble substances, but cocoa is a mixture of water soluble components and insoluble small particles. These insoluble particles (about 10 micrometers) show sedimentation and are thus not stable in the hot chocolate. If the insoluble particles could be made small enough (sub-micron, down to 100 nanometres) it should be possible to have or to create colloidal stabilisation. In that case, the ‘insoluble’ cocoa is dispersed next to the molecularly dissolved part of the cocoa, and could be considered ‘soluble’. www.newfoodmagazine.com

[jeffreyH]

This calls for a kitchen science experiment. If you could isolate a tannin from the tea and add cocoa ...

[petelamana]

I'm doing a quick study of tannins...love this site for the inspiration it gives me to learn...anyway, as I said, I am doing some additional reading on this topic.  I believe I understand why the tannin-cocoa correlation was brought forward, however apparently cocoa (chocolate) also contains a level of tannins.  So, I'm not sure how removing the tannins from the tea would affect cocoa's solubility.

  (chocolate, my favorite vice)