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Experimental Overview  
This is a follow up post to my Fat Replacements in Boxed Brownies experiment, where I found that Sweet Potatoes were the best replacement for butter or oil in a box of brownie mix. The texture of the baked sweet potato brownies most represented the control of butter, being chewy, structurally sound, and not over or under baked. The flavor was unmatched, as the sweet potato brownies were far and away the best ones on the table, even over the control.

This part 2 serves as a larger test of sweet potato brownies. In it, I have taken a box of Duncan Hines Dark Chocolate Fudge brownie mix. I will divide the mix in half, baking one half according to the instructions, and the other half replacing the fat with sweet potato. As my other taste tester tonight has a nut allergy, the keto box (with almond flour) was off the table. Plus, this will give us a test with more standard sugar filled brownies; we'll see if sweet potatoes still hold up.

The Brownie Box  





As mentioned above, the boxed brownies being tested are the Duncan Hines Dark Chocolate Fudge. The photos of the box are above, showing the packaging, nutrition facts, recommended substitutions, and baking instructions. The box has a weight of 518.4 g. A full batch of brownies calls for 1/3 cup (80 g) water, 1 large egg (53 g), and 1/2 cup (112 g) vegetable oil. As the mix is getting split 2 ways, that means that each bowl should get:

1. 259.2 g brownie mix
2. 1/6 cup or 40 g water
3. 1/2 egg or 26.5 g egg
4. 4 tbsp or 56 g oil


These are the amounts that will go in the control batch, and the experimental batch will get an equivalent amount by volume of sweet potato instead of oil.

Control & Experiment  
1. Canola Oil
2. Sweet Potato Puree

Ingredients
1. Canola Oil


This is the standard experiment. In a small bowl goes the brownie mix, water, egg, and oil. The batter was stirred together, and poured into a parchment lined and greased 8" pan. This will be the basis of our experiment, as it will provide a frame of reference for the other trial.



Ingredients
- 1/2 package (260 g) duncan hines dark chocolate fudge brownie mix
- 1/4 cup (56 g) Oil, canola
- 1/2 egg (26.5 g) Egg
- 1/6 cup (40 g) Water

2. Sweet Potato Puree


Earlier, I made a small batch of Roasted Sweet Potato Puree in preparation for this. I just poked 2 potatoes with a fork, wrapped it in foil, and air fried it at 400F for 75 minutes until soft. I cut them in half, let them steam out and totaly cool, and blended the insides it into a smooth puree. Canned pumpkin puree would also work, as well as Roasted Butternut Squash Puree.


For the sweet potato, the conversion is the following:
1 cup oil = 1 cup (255 g) sweet potato

Therefore, for the 4 tbsp oil, I will need 63.75 g mashed sweet potato.



Ingredients
- 1/2 package (260 g) duncan hines dark chocolate fudge brownie mix
- 1/4 cup (64 g) Sweet potato puree
- 1/2 egg (26.5 g) Egg
- 1/6 cup (40 g) Water

Mixing & Baking  
The two batches were measured and mixed in separate bowl. Note that the texture of the sweet potato bowl was noticably a bit thicker than the bowl with oil. I am legally requried to say that you are not supposed to consume raw brownie batter. And with that out of the way, both the raw batters tasted great with no real difference there.

The batter was poured into a parchment lined and greased 8" pan. Each was baked at 350F for 16 minutes, or until a toothpick was almost fully clean. Each of the 2 8" pans would be cut into 16 brownies, making a total of 32.




The baked brownies were transferred to the fridge to cool totally in the pan for a few hours before slicing.

Taste Test  
Finally, (the moment we've been waiting for), the brownies were assessed on their appearance, texture, and taste. Meaning, it was finally time to eat.



1. Canola Oil
The standard brownies were great. Nice and fudgy interior, lightly crispy edges, great taste, and a good brownie skin on top. It was a bit too sweet for my taste, but still very good. Not the best brownie in the world, but solid for a box brownie. 7.5/10

2. Sweet Potato Puree
I'm sad to say that sweet potatoes won't be winning any awards here today. The texture was a bit cakey and spongy, and the taste was bland. In the keto brownies, you could mildly taste the sweet potato, and it was sweeter as a result. In these however, it almost more like eating a Fiber One brownie than a real brownie, but still with all the sugar and none of the fiber. 3.5/10

Conclusion  
While sweet potatoes can work as a fantastic fat replacement in keto brownies, the same cannot be said for traditional brownies. In comparing both, I think I still side with the sweet potato keto brownies as being the best tasting, even over the oil and sugar brownies.

If we're comparing the sugar brownies to the keto ones, I'd say that the canola oil ones would land above the yogurt keto brownies (7.5/10), but below the sweet potato keto brownies (9/10). On the other hand, the sweet potato traditional brownies would slot below the keto black bean brownies (4/10) for the bottom ranking. :(

My guess is that the lack of fat in the sweet potato regular brownies above lead to a cakey texture and a bland taste. On the other hand, the sweet potato keto brownies had fat from the almond flour, leading to a much more traditional brownie texture and taste. More fat would also help in keeping the brownies moist and fudgy, whereas an absense of fat would lead to a dry baked good, which is exactly what we saw.

For a homemade healthy brownie using sweet potatoes, you should check out my Sweet Potato Brownies (SF). They're homemade instead of from a box, so they avoid a lot of ultra processed ingredients. They're still gluten free (and this time nut free!), can be make keto by using almond flour instead of oat flour, and are still lower in fat and sugar while still being just as delicious.

Sources  
1. Fat Replacements in Boxed Brownies