Why is dark chocolate dark when pure cocoa is light brown?

Question

Kind of a simplistic question, but my curiosity cannot be assuaged. When you look at pure cocoa powder, it has a light brown color, like a milk chocolate bar. And yet a dark chocolate bar, which is much higher chocolate content than milk chocolate, is a vastly darker color than cocoa powder. Even a 100% pure cocoa chocolate bar is a very dark color.

Pure cocoa powder

Milk chocolate bar

Dark chocolate bar ~75% cocoa

Dark chocolate bar 100% cocoa

What is at work here? I know chocolate has fats and solids other than cocoa in it, but that just makes it more confusing why a pure chocolate bar is dark as well. Does compacting the cocoa into a solid form (which is how I assume you make a pure cocoa bar) darken it that much? Are there differences in preparing the cacao beans (like different roasts for coffee)?

Answer 1

There are probably several factors in play:

1. The chocolate liquor used to make the chocolate may have been dutched (processed with alkali) which makes it darker. AT the extreme end, it is almost black, like an Oreo (which is made with highly dutched cocoa).

2. The fat phase surrounds the cocoa particles, and makes them appear darker, much like wetting cocoa powder with water makes it appear darker.

3. The cocoa used to make the chocolate may be roasted to a greater or lesser degree, which affects its color, might like with coffee. Thanks to Didgeridrew for pointing this out.

4. Milk chocolate is necessarily lighter, as the milk particles are white, and help make the entire bar a lighter shade.

The cacao percentage is not a major factor, as even low cacao chocolates (like the very, very sweet German's Baker's Bar) are quite dark.

Answer 2

It's because the cocoa is a powder. It's reflecting more light. If you have access to any wax, think about how it turns white when you scratch it or how if you break a candle you will see white on the broken surface. If you add cold water to cocoa powder and stir patiently you will see a glossy dark brown colour like the dark chocolate.

Possibly interesting: a research paper explaining the physics of why things are darker when they are wet. This link was in a comment to an answer to a more general question on Physics.se.

Answer 3

Your assumption seems to be that the color of a substance should be the same, no matter in what phase its matter is. This assumption is not true in general. For example, a block of sugar is transparent, but powdered sugar is white. Egg yolk is a saturated yellow, but egg yolk foam is whitish pale.

The different color is not explained purely by the fact that it is in a different form. If you grate a chocolate bar, it will change its color, but to a more grey-whitish one, not to the redder one in your picture. Here, the different composition of elements and the chemical change of elements (both explained in SAJ's post) certainly play a big role. But even if this wasn't the case, the color wouldn't stay the same.

Answer 4

Roasting the brown cacao power turns it dark and destroys many of its nutrients. Raw cacao after being fermented and dried is the best form and retains the nutrients that are desirable for this super food.

Answer 5

because of roasting. Commercial chocolate comes from mostly quite cheap beans, often in african countries with poor quality beans. The chocolate needs to be "over roasted" to kill off not only the bacteria (on ALL beans even good quality ones) AND also the off flavors that come from having not been properly fermented and dried! some commercial chocolate is almost black at 80%. Compare it to an 80% bar from a bean-to-bar manufacturer and you will notice the difference