Ok, I've only ever made chocolate cakes using only or mainly melted chocolate but recently I've been looking for a devil's food cake. The first recipe I made smelled like Ammonia, I kid you not! It called for 2 tsp of baking soda and 3/4C of natural cocoa, no more acid (that should have been my clue). Trashed it. Taste-wise it was a good, normal tasting chocolate cake but that smell-- yes I tasted it. I am my own guinea pig first. Always.

I only have natural cocoa so I made Martha Stewart's One-Bowl Chocolate cake which is pretty much identical, it calls for 2 tsp baking soda, 1 C natural cocoa, except it has extra acid (1C buttermilk instead of plain milk). I love the cake, tastes great BUT why does it smell different? Not Ammonia this time. It's a sort of earthy, cocoa meets baking soda meets something else in the batter, almost organic-y. Can't put a finger to it but this cocoa cake smells its nothing like the 'chocolate' smell I'm used to with melted chocolate cakes.

To be sure my leaveners and cocoa were okay, I did a mix in a cup, heated in microwave to activate the cocoa, baking soda and powder, no weird smell, baking powder okay, activated when the mixture was heated, cocoa darkened as expected. So the cocoa, and leaveners are fine.

Could it be that the cake has too much baking soda? Or are natural cocoa chocolate cakes supposed to smell well, um, different?

Update: Hopefully this will help someone some day. 3 days of digging through cook books, googling, baking--5 tries and 9 cakes--later, it turns out the culprit was the espresso powder. I ended up baking two other chocolate cake recipes that used similar ingredients with baking soda ranging from 1tsp to 2.5 tsp for an equal amount of flour. Neither had the weird smell, thus eliminating everything BUT the espresso powder, as the weird smelling cake had this in it.

Next, Googled "espresso/coffee and ammonia" and found some correlation between old and/or poorly processed coffee and ammonia smells. Even though my espresso powder showed an expiration date of January 2014. It's since been trashed.

Man, THIS is why I love the science of baking. I thank God this mystery is resolved. The final batch of cakes are in the oven now. Halleluyah!

P.S. An extra perk of all this hard work, wasted ingredients (I used up just about all my fancy Penzy's cocoa) and God help my energy bill, is that I understand cocoa, and chocolate cakes, devil's food cake and acid-base balance in cakes a whole lot more now. 

Where is Shirley Corriher when you need her?

Instead of CSI you are BSI baking scene investigation.. good job