In 2011 I visited the Cointreau distillery in Angers, France. I wrote about that here. After I returned I realized I had a few more questions.
Luckily, Cointreau's Master Distiller Bernadette Langlais was in San Francisco last night so I had a chance to clarify some questions about the centrifuge part of the process.
To recap, Cointreau is made by steeping orange peels in high-proof neutral beet sugar alcohol and distilling it. This 'raw alcoholate' is reduced with water, centrifuged, then reduced with more water, more neutral alcohol, and sugar before filtration and bottling.
The centrifuge step was curious to me, so I asked Langlais for some clarification. She told me that this step removes some essential oils from the alcoholate.
But then why not just use less oranges in the first place to have less essential oils?
It turns out that they use the centrifuge (which is a continuous centrifuge, by the way, not a batch process) to remove only certain essential oils. Surprisingly, they are not removing heavy ones that would collect at the outside of the centrifuge (a centrifuge separates by weight), but the lightest, zesty oils.
Langlais said this was so that there is a proper balance between the 'juicy' flavors and zesty ones in Cointreau. If they left everything in, the liqueur would be overwhelmingly zesty.
I also brought up the topic of Cointreau in Brazil and Argentina, where it is made with sugar cane alcohol and cane sugar, instead of beet sugar. This is due to local tax regulations that would make Cointreau prohibitively expensive if they used their regular beet sugar. I learned that they make the same 'raw alcoholate' (high-proof orange-infused alcohol) at the distillery in France and ship that to the local countries. There, they add more (cane) alcohol and (cane) sugar before bottling.
Langlais said that it tastes the same as regular Cointreau. She also said that the sugar from cane or beets tastes exactly the same, and the more important part of the equation is the alcohol, even though it is 96% alcohol and supposedly neutral in flavor.