What makes Oreo cookies black – On cocoa powder science

Oreo cookies are that type of cookie that’s combined with everthing and used for all sorts of baked goods. There’s Oreo cookie ice cream, Oreo cookie pie crust, etc. The super black outer cookie with the snow white gooey inside make it look different than a lot of cookies out there. It especially doesn’t look like a chocolate cookie, to me at least. Chocolate? You might ask. Yes, the outside of Oreo’s strictly are chocolate cookies, that is, they contain cocoa powder (besides flour, sugars, fats and some other minor components). Honestly, if you’d asked me that several years ago, I wouldn’t have known.

Also, Oreo cookies do not contain any colourant. The only probably origin of that black colour actually is the cocoa powder. All in all, it’s about time we start discussing cocoa powder science. Why are Oreos so black, whereas your homemade chocolate pie made with cocoa powder certainly is more brown than black.

Oreo cookie ingredients

As quickly mentioned at the start, Oreo cookies don’t contain a lot of colouring molecules. The Dutch cookies (in other countries ingredient lists might be different) the Oreo cookies contain about 4,6% of skimmed cocoa powder. Besides that they contain flour (main ingredient), sugars, fats (palm oil), leavening agents and some salt, emulsifier and aroma.

It really is the cocoa powder that has to make up the colour of the cookie. The flour creates the basic structure together with the sugar and the fats. The leavening agents make sure the cookie is not a brick, but is crumbly and crunchy instead. The salt and aroma are there for flavour and the emulsifier (lecithin) is most likely there because of processing reasons. Lecithin makes it easier to mix fats with water and create a stable dough in a factory.

Cocoa powders

Thus we should dive into cocoa powders in more detail. Cocoa powders are made from cocoa beans. After fermenting, drying and roasting the cocoa beans at some point in time the cocoa has to be taken out of the beans. In order to do this the cocoa beans are milled. This makes so-called cocoa mass. Cocoa mass is a mixture of cocoa butter (a fat) and dry cocoa ingredients (a mixture of a lot of different components). Cocoa mass is quite bitter, very dark chocolate is made off barely anything else than cocoa mass.

Cocoa powders are made from cocoa mass by pressing out the cocoa butter. This results in a drier powder which still contains some fat, but a lot less than the initial cocoa mass.

Once the cocoa mass has been pressed the powder is finished and flavour will not change that much anymore. All flavour development has been done in the steps before converting the cocoa beans into cocoa mass and cocoa powder. This can result in very different cocao powder flavours!

Alkalization

Before the transformation of beans into powders takes place, there can be another another step in between: alkalization. This process was discovered more than a 100 years ago by a Dutch manufacturer, van Houten. He discovered that by adding some alkali (products with a high pH) to the slightly acidic (pH 5-6) cocoa beans would improve their flavour (read more about pH and bases & acids here). The alkalization process would make it less bitter, but also change the colour of the product.

The extent of the impact depends on the concentration of the alkali used. Using a lot of alkali will increase the pH further than using a limited amount which will impact both flavour and colour.

sedimentation experiment chocolate milk 10 min
Using cocoa powder to make chocolate milk, in this case alkalized cocoa powder was used. It also seems to be easier in use for making chocolate milk drinks.

Impact on colour

Alkalization darkens the colour of cocoa powder. The extent in which the colour is affected depends on a variety of factors at play here. For instance, a higher temperature of the process is generally linked to a darker cocoa colour. Also, the origin of the beans, moisture content and air quality influence the final outcome of the process (source).

When the conditions are chosen correctly it is actually possible to make a pitch black cocoa powder, like the one that’s used for Oreo’s. That said, the Oreo cookies most like contain at least one other cocoa powder. The flavour of the black cocoa powder might not be as strong anymore.

To me, that also explains why Oreo’s don’t really taste like chocolate. The cocoa powder has been processed in such a way that the flavour has greatly changed.

Innovation in alkalization

In order to perform alkalization of the cocoa beans some sort of an alkali has to be added. Common alkali used are ammonium carbonate with iron salts. These components aren’t the best to use from an environmental and safety perspective, which is why research is being done in finding replacers. The producer of Oreo filed a patent a few years ago stating an improved production method to do so, using more environmentally friendly alkali.

Sources

In case you didn’t check the patent on making black cocoa powder yet, here‘s the link again. David Lebovitz also wrote a nice article on the topic.

 

2 Comments

    • Scienchef

      Hi Felicity,

      You’re question made me have a thorough look at Oreo cookies again and I guess you could both say they’re black as well as super dark brown. So, if you see them under artificial lighting they look pretty black to me. But in sunlight they do look very very dark brown, especially when I compared them to Hydrox cookies (almost the same as Oreo’s, but different brand), compared to those Oreo’s actually look a little brownish :-).
      The reason behind them being so super dark stays the same though :-)!

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