Maybe NOT a Whole Wheat Flour Question
So... searching for Whole Wheat Flour nets about 100 topics. I feel awkward doing this. I didn't find the answer to my question in any of the ones I checked, so, I'm hoping this is not necessarily heavily tread material.
I tried to integrate King Arthur's Whole Wheat into my biscotti recipe this morning. The dough felt good, first baking went well but when I went to cut it it turned into breadcrumbs. Not fun. I used a 50/50 blend of wheat and white flour by weight.
I just tried an Irish Soda Bread, again 50/50. While it held together much better, it was on the fairly 'crumbly' side.
Two quick breads, similar results. Frankly I've never had this happen to me before, I'm not much of a baker, so I don't know how to diagnose the problem. Using Google hasn't really helped much so...
Is it an under-kneading issue? I prepared them both like I normally do, which isn't with a lot of kneading.
Might it be a liquid issue?
Any thoughts are welcome. Sorry if I'm beating the nutrient rich dirt where a horse died and was beaten to fertilizer years ago.
Greygarious is correct when she states that whole wheat flour absorbs more liquid than white. The switch to white whole wheat flour may solve your problems. Whole wheat pastry flour might be better than regular whole wheat, as well; it's a soft wheat, low protein flour and will give you a more tender crumb.
I also think you may possibly have overbaked the biscotti, as I have eaten biscotti made with a 50/50 ratio of white to whole wheat flour which didn't turn into breadcrumbs when sliced. The overbaking is just a guess on my part; without seeing your recipe, I can't really comment futher.
The second issue is possibly the amount of liquid (eggs) in the recipe. You may have to add a little milk with the whole wheat flour dough to ramp up the moisture content.
I assume you are aware that biscotti are normally quite crunchy and are meant to be dipped in coffee or vin santo or something, but it sounds like yours were way past crunchy.
Here are a few links for biscotti made with varying amounts of whole wheat flour, and some interesting add-ins. I'm sure the basic dough can be made without the add-ins. Take a look and compare them with your formula:
This recipe from Martha is the same as above, with different add-ins:
This recipe is 100% whole wheat and mentions that the dough, containing 3 eggs, may be sticky and might need a bit more flour:
This link, adapted from Dorie Greenspan, uses whole wheat pastry flour and cocoa for what sounds like a very nice chocolate biscotti. Use natural cocoa in this recipe:
So, there you have a few biscotti options.
Here's a link for the KAF Irish Soda Bread, made with whole wheat and bread flour. I've made this and it's very good, dense and hearty, much like what I had "over there" Soda bread should be farily moist, but not so much as a quick bread. The KAF site also has a recipe for an Irish Soda Bread Cake, which is made with pastry flour. I made that version as well, subbing AP flour, and it was nice and moist, with a tender crumb. The recipe contains a fair amount of butter for moisture and tenderness; perhaps you could try the cake version with 75:25 white to whole wheat:
I provided these links as a way for your to compare your recipe against others. I am not pimping KAF particularly, or any of the links generally, although a number of the KAF site recipes are very good, as are their flours.
A little regular whole wheat flour goes quite a ways in baked goods.
Check out the King Arthur recipe page on their website. I know they have several Irish soda bread recipes and they have biscotti recipes. Compare them with yours and maybe you can find an answer. I use their Irish wholemeal flour for my soda bread (not their recipe) and it comes out quite moist. I've never made biscotti.