can anyone explain chocolate?

[eub]

It seems to exist in at least two different solid phases, "solid tempered" (dark and shiny) and "solid untempered" (tan and crumbly). Descriptions of the tempering procedure suggest that liquid tempered chocolate is stable between 83 and 95 °F, while untempered chocolate is solid up to 115. When it melts (into untempered liquid chocolate?) it can be converted to liquid tempered chocolate by adding chunks of solid tempered chocolate. (By rapid cooling? Or one recipe says it's seeded crystallization; I could buy catalysis anyway.) Or by cooling with stirring, apparently. But I've certainly seen that cooling by letting it sit out leads to untempered crud. On the other hand, we know liquid tempered chocolate can cool to solid tempered chocolate -- maybe when it's cooled faster?

What are the thermodynamic phases reached in cooking with chocolate? I wonder if the tempered solid phase is only metastable. I guess I want a phase diagram that also sketches the metastable regions.

Comments

[ralphmelton.livejournal.com]

I just read the discussion in Cookwise last night. It is indeed very nifty. It doesn't provide a full phase diagram, but it does point out that the 'tempered chocolate' form is the beta crystal structure, as opposed to gamma, delta, or beta prime. (I wonder what happened to alpha.)