My applesauce quick bread tastes like baking soda. Why? I've used the recipe before with no problem. In this batch I used homemade applesauce.

Antonia I am so happy you have stumbled upon something new and delightful! I would love to see the recipe here :D

Okay, just to follow up . . . I made this recipe again last night, using chunky applesauce from the same batch. I was short by about 1/3 a cup, and I just happened to have some buttermilk on hand (having just made my Buttermilk Oatmeal Bread . . . I usually do a quick bread with my at-least-weekly yeast bread), so I added that. The bread is outstanding. Problem solved! I'm inclined to post it as a new recipe, it was so good. Thanks so much for your help, everyone! ;o)

I normally would add a teaspoon of apple cider vinegar, or a bit of yogurt to ensure there's acid in the mix. I'm one of those extraordinary tasters of baking soda - even in the tiniest amounts so I take precautions to avoid tasting its acrid side!

Is it at all feasible that you measure wrong?

I'm betting your batch of applesauce is less acidic. I'd try 1/4 t baking soda and 1 T baking powder for you next batch.

Hmm your recipe looks all right to me. I would try using only 1/2 teaspoon baking soda or switching it out for baking powder. You know it could also have just been a fluke. Baking is such a science and all number of things can happen like your flour had more/less moisture in it than usual or your eggs were a slightly different size. I left a link below that has a lot of good information on leaveners, maybe you can glean some useful knowledge from that.
http://baking911.com/learn/ingredients/leaveners
Good luck with your next batch!

RespectThePastry, thank you so much. I have adapted the banana bread recipe from The Tassajara Bread Book for years, substituting applesauce, homemade fruit jams when I have a lot of extra on hand, etc., for the bananas. Recipe: Beat 1/2 c. oil with 1/2 c. brown sugar. Add two eggs and a tsp vanilla and beat well to combine. In a separate bowl, mix 2 cups flour, 1 teaspoon baking soda, 1/4 teaspoon salt. (I usually add a hefty dash each of cinnamon and allspice here.) Mix dry ingredients into wet ingredients in thirds alternately with 2 cups mashed bananas. (I substitute applesauce 1:1.) Stir in nuts and raisins; bake at 350 for 25 minutes for four mini loaves.
I'm quite sure the baking soda was measured correctly.
Thank you so much. ;o)

Baking soda is meant to react with an acid (when it becomes wet) and create the texture and crumb of your quick bread. I would say that your baking soda did not react with the acid in the way it should have, unless it was accidentally measured wrong, this is the likely reason it caused the soapy flavor in your quick bread. If you list your recipe, I may be able to better pin point what could have caused the problem.