Hello, expert bakers, I'm hoping someone out there will be able to explain why I got this result.

So, I was experimenting with the following recipe to see if I could make it more consistent. It's an old family favorite that was originally baked in a tube pan and I love the flavor so I've been trying to figure out how to use it for layer cakes.

Here's the original: Chocolate sour cream pound cake
Cream:
3 sticks butter
3 c. sugar

Add 1 at a time:
5 eggs

Mix dry, add alt. with sour cream
3 c. unbleached all purpose flour
1/2 c. cocoa powder (reg. not dutched)
1 tsp. baking soda
1/4 tsp. salt
8 oz. sour cream

Mix in:
1 c. boiling water
2 tsp. vanilla

The only changes I made were to sub cake flour for the unbleached all-purpose (by weight, not volume) and coffee for the water. I'd always made this with unbleached all-purpose, but since I'd read that bleached flour was better for cakes, I wanted to try it that way and see what happened.

Baked at 325 in two ten in. round pans, the cake domed quite a bit, but looked fine when I took it out. When I cut off the dome, there were enormous (larger than the tip of my thumb) holes throughout the cake. This recipe is normally very fine textured. The cake was also much fluffier, almost to the point of being dry, whereas it is normally extremely moist.

My first thought with the holes was uneven distribution of leavening, but I sifted together the dry ingredients, and then whisked them until the cocoa color was even, so I doubt that is the problem. I'm stumped as to why I got these results. So what do you guys think?

Anyone know of a baking chemistry explanation for these results?

I've got a chart like this in my cake bible:

http://www.wilton.com/blog/index.php/obtaining-better-baking-results-a-baking-troubleshooting-guide/

http://www.joyofbaking.com/ButterCakeTroubleshooting.html

I'm not a pastry chef....but I use this to tweak my recipes when something goes wrong.

[quote="Blueridgebuttercream"
The only changes I made were to sub cake flour for the unbleached all-purpose (by weight, not volume) and coffee for the water. I'd always made this with unbleached all-purpose, but since I'd read that bleached flour was better for cakes, I wanted to try it that way and see what happened.
[/quote]

The switch in flour is probably part of the problem. It is not the case that cake flour is always better for cakes. It is better in particular cake recipes--particularly those with hi ratio of sugar/water. In this recipe the ratio of flour to sugar looks 1 to 1 so not a high ratio recipe.

In addition cake flour and AP flour have different protein contents--around 11% for AP and 6-8% for cake flour. This difference can result in dramatically differences when one is substituted for the other. This is also why substitutions are not one for one--volume or weight. In this instance the less protein would result in a lighter cake--which is consistent with the results you report.

I doubt the substitution of coffee made much of a difference as it has a relatively neutral ph.

You MUST use AP flour with the original recipe. Unbleached works best in my experience.

Reason #1: the cocoa powder has no gluten, and it lowers the effective gluten of the flour. Total gluten content of flour plus cocoa is close to pastry flour.

Reason #2: you need AP flour to hold up the extra load of sour cream and sugar.