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Experimental Overview  
Have you ever made boxed brownies, and thought "how can I make this healthier?" The side of the box typically has some substitutions, like replacing the egg for grated zucchini or the butter for applesauce, but today I wanted to put some common substitutes to the test. I'll be taking a box of Duncan Hines Keto boxed brownie mix (pictured below), which is both sugar free and gluten free. Yes, this test would have been cheaper and easier if I was using a standard box of brownies (it was about $6.50 for the keto box, as opposed to under $2 for the regular). But what's the point of swapping out the fat in the brownies, making them marginally healthier, but still leaving all the sugar? That's my main problem with a lot of bean brownie recipes; cool there's no oil, but there's still a cup of sugar. No good in my book.

My original plan was to purchase a new box for each experiment, and to test both the control and all my experiments on their own boxes in a full batch of brownies. But not only would that have been expensive, I also would have had 6 full batches of brownies to get through. So instead, I've decided I would use 1 box of mix, and divide the contents 6 ways - 1 for the control, and 5 experiments. I'll then scale the recommended ingredients down to 1/6 of their original values, and mix together the batters in 6 smaller bowls. The brownies will be baked as mini muffins, and tested with a toothpick for doneness (as the box doesn't have baking time for mini muffins). Finally, each of the different types of brownie will be put on their own plate, and labeled with a post it underneath. The plates will be shuffled around, that way the participants (myself, my girlfriend Vic, and our friend Cass) won't know which ones we are tasting. The brownies will be roughtly judged based on their appearance, texture, and, most importantly, taste.

One final note - the eggs will also be swapped out in the recipe, in addition to the butter. This is for 2 reasons. Firstly, dividing 2 eggs 6 ways equally isn't exactly feasable or accurate. The control batch will still get 1/3 of an egg, but the experimental batches will have their egg replaced with an equivalent amount of their butter substitute. This leads into the second reason - a lot of the egg replacements I've seen are actually the same as butter/oil replacements - applesauce, yogurt, mashed banana, etc. Note that 1 egg is typically about 1/4 cup of those replacements, but will vary based on the substitution. Okay, now it's finally brownie time.

The Brownie Box  





As mentioned above, the boxed brownies being tested are the Duncan Hines Keto brownie mix. The photos of the box are above, showing the packaging, nutrition facts, recommended substitutions, and baking instructions. The box has a weight of 270.3 g. A full batch of brownies calls for 1/3 cup (80 g) water, 2 large eggs (100 g), and 6 tbsp (85 g) melted butter. As the mix is getting split 6 ways, that means that each bowl should get:

1. 45.13 g brownie mix
2. 13.33 g water
3. 16.67 g egg
4. 14.2 g melted butter


These are the amounts that will go in the control batch, and the experimental batches will get an equivalent amount by volume of those ingredients. As mentioned above, 1 egg is approximately 1/4 cup of the substitutions, meaning 1/3 egg would be about 2 tsp of the egg replacement. Each batch will however get the same amount of water (except for the beans, which will be discussed below).

Control & Experiments  
1. Butter and Eggs
2. Unsweetened Applesauce
3. Plain Nonfat Greek Yogurt
4. Mashed Banana
5. Sweet Potato Puree
6. Black Bean Puree



Ingredients  
1. Butter & Eggs
This is the standard experiment. In a small bowl goes the brownie mix, water, egg, and melted butter. The batter was stirred together, and poured into a greased mini muffin tin. This will be the basis of our experiment, as it will provide a frame of reference for the other 5 trials.

Ingredients
- 1/6 package (45 g) Duncan Hines Keto Brownie Mix ($0.95)
- (14.2 g) Unsalted butter ($0.11)
- (16.67 g) Egg ($0.04)
- (13.33 g) Water ($0.00)

Nutrition Facts
------------------------------------------
Servings: 4
Calories: 87
------------------------------------------
Total Fat: 5.0g (6 %)
 Saturated Fat: 2.4g (12 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0.1g
 Monounsaturated Fat: 0.2g
Cholesterol: 25mg (8 %)
Sodium: 33mg (1 %)
Total Carbohydrate: 8.0g (3 %)
 Dietary Fiber: 2.5g (9 %)
 Sugar: 0g
Protein: 2.0g (4 %)
------------------------------------------
Vitamin B12: 0.0mcg (2 %)
Vitamin D: 0.1mcg (0 %)
Potassium: 106mg (2 %)
Calcium: 2mg (0 %)
Magnesium: 1mg (0 %)
Iron: 0.8mg (4 %)
------------------------------------------
 Glycemic Index: 51.0
Glycemic Load: 3.1
 
2. Unsweetened Applesauce
Applesauce is often used as a butter or oil replacement in lots of healthy baked goods. It provides moisture, sweetness, and richness, without all the fat and calories of butter. It's allergen friendly, cheap, and easy to use. I imagine that using No Sugar Added Apple Spread instead of storebought unsweetened applesauce would be even better, but I have not tested it here.

For the applesauce, the conversions are the following:
1 egg = 1/4 cup (61.25 g) applesauce
1 cup butter = 1 cup (245 g) applesauce

Therefore, for the 1/3 egg and 1 tbsp butter, I will need 20.42 + 15.31 = 35.73 g unsweetened applesauce. This batch will get the same 13.33 g water as well, like most of the other batches.

Ingredients
- 1/6 package (45 g) Duncan Hines Keto Brownie Mix ($0.95)
- (13.33 g) Water ($0.00)
- (35.73 g) Unsweetened applesauce ($0.08)

Nutrition Facts
------------------------------------------
Servings: 4
Calories: 59
------------------------------------------
Total Fat: 1.8g (2 %)
 Saturated Fat: 0.5g (3 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0.0g
 Monounsaturated Fat: 0g
Cholesterol: 0mg (0 %)
Sodium: 28mg (1 %)
Total Carbohydrate: 9.0g (3 %)
 Dietary Fiber: 2.6g (9 %)
 Sugar: 0.8g
Protein: 1.5g (3 %)
------------------------------------------
Vitamin B12: 0mcg (0 %)
Vitamin D: 0mcg (0 %)
Potassium: 107mg (2 %)
Calcium: 1mg (0 %)
Magnesium: 0mg (0 %)
Iron: 0.7mg (4 %)
------------------------------------------
 Glycemic Index: 48.9
Glycemic Load: 3.5
 
3. Plain Nonfat Greek Yogurt
I was the most excited for this one, as not only is this substitution actually recommended on the box (as well as the applesauce), but from other sources I've read (linked below), yogurt seems to be the favorite swap. It cuts down on the fat and calories, while also adding some protein. I would assume that blended nonfat cottage cheese would work as well, though it may come out a bit salty.

For the yogurt, the conversions are the following:
1 egg = 1/4 cup (56.67 g) yogurt
1 cup butter = 1 cup (226.67 g) yogurt

Therefore, for the 1/3 egg and 1 tbsp butter, I will need 18.89 + 14.17 = 33.06 g plain nonfat greek yogurt. This batch will get the same 13.33 g water as well, like most of the other batches.

Ingredients
- 1/6 package (45 g) Duncan Hines Keto Brownie Mix ($0.95)
- (13.33 g) Water ($0.00)
- (33.06 g) Plain nonfat greek yogurt ($0.13)

Nutrition Facts
------------------------------------------
Servings: 4
Calories: 60
------------------------------------------
Total Fat: 1.8g (2 %)
 Saturated Fat: 0.5g (3 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0.0g
 Monounsaturated Fat: 0.0g
Cholesterol: 0mg (0 %)
Sodium: 31mg (1 %)
Total Carbohydrate: 8.3g (3 %)
 Dietary Fiber: 2.5g (9 %)
 Sugar: 0.3g
Protein: 2.3g (5 %)
------------------------------------------
Vitamin B12: 0.1mcg (2 %)
Vitamin D: 0mcg (0 %)
Potassium: 112mg (2 %)
Calcium: 9mg (1 %)
Magnesium: 1mg (0 %)
Iron: 0.7mg (4 %)
------------------------------------------
 Glycemic Index: 50.3
Glycemic Load: 3.2
 
4. Mashed Banana
Bananas are probably the most common egg replacement in brownies and other box mixes. In fact, I was surprised to see grated zucchini listed as an egg swap on the box instead of banana. Overripe bananas are sweet and delicious, but will presumably leave the brownie with a slight banana flavor, which is either a pro or a con. To prevent chunks, I blended the banana smooth in my hand blender.

For the banana, the conversions are the following:
1 egg = 1/4 cup (56.25 g) mashed banana
1 cup butter = 1 cup (225 g) mashed banana

Therefore, for the 1/3 egg and 1 tbsp butter, I will need 18.75 + 14.06 = 32.81 g mashed banana. This batch will get the same 13.33 g water as well, like most of the other batches.




Ingredients
- 1/6 package (45 g) Duncan Hines Keto Brownie Mix ($0.95)
- (13.33 g) Water ($0.00)
- (32.81 g) Banana, overripe ($0.04)

Nutrition Facts
------------------------------------------
Servings: 4
Calories: 62
------------------------------------------
Total Fat: 1.8g (2 %)
 Saturated Fat: 0.5g (2 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0g
 Monounsaturated Fat: 0g
Cholesterol: 0mg (0 %)
Sodium: 28mg (1 %)
Total Carbohydrate: 9.7g (4 %)
 Dietary Fiber: 2.6g (9 %)
 Sugar: 0g
Protein: 1.6g (3 %)
------------------------------------------
Vitamin B12: 0mcg (0 %)
Vitamin D: 0mcg (0 %)
Potassium: 100mg (2 %)
Calcium: 0mg (0 %)
Magnesium: 0mg (0 %)
Iron: 0.7mg (4 %)
------------------------------------------
 Glycemic Index: 51.2
Glycemic Load: 4.1
 
5. Sweet Potato Puree
Yesterday, I made a small batch of Roasted Sweet Potato Puree in preparation for this. I just poked the potato with a fork, wrapped it in foil, and air fried it at 400F for 1 hour until soft. The next day, I scooped out the insides, and blended it into a smooth puree. Canned pumpkin puree would also work, as well as Roasted Butternut Squash Puree.

For the sweet potato, the conversions are the following:
1 egg = 1/4 cup (63.75 g) sweet potato
1 cup butter = 1 cup (255 g) sweet potato banana

Therefore, for the 1/3 egg and 1 tbsp butter, I will need 21.25 + 15.94 = 37.19 g mashed sweet potato. This batch will get the same 13.33 g water as well, like most of the other batches.




Ingredients
- 1/6 package (45 g) Duncan Hines Keto Brownie Mix ($0.95)
- (13.33 g) Water ($0.00)
- (37.19 g) Sweet potato puree ($0.12)

Nutrition Facts
------------------------------------------
Servings: 4
Calories: 64
------------------------------------------
Total Fat: 1.8g (2 %)
 Saturated Fat: 0.5g (3 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0.0g
 Monounsaturated Fat: 0.0g
Cholesterol: 0mg (0 %)
Sodium: 35mg (2 %)
Total Carbohydrate: 10.2g (4 %)
 Dietary Fiber: 2.7g (10 %)
 Sugar: 0.5g
Protein: 1.7g (3 %)
------------------------------------------
Vitamin B12: 0mcg (0 %)
Vitamin D: 0mcg (0 %)
Potassium: 120mg (3 %)
Calcium: 3mg (0 %)
Magnesium: 2mg (1 %)
Iron: 0.8mg (5 %)
------------------------------------------
 Glycemic Index: 60.4
Glycemic Load: 5.0
 
6. Black Bean Puree
Finally, here comes the beans. This will be the exception, as this one will not include the water. This is because for the bean puree, I blended an entire 15.5 oz can of black beans, not drained or rinsed. The liquid in the can of beans will also be the water in the brownies. I could not find unsalted canned black beans, so hopefully this doesn't come out too salty.

I will replace the water, eggs, and butter with an equal amount by weight of the blended bean puree. Therefore, I will need 13.33 + 16.67 + 14.2 = 44.2 g black bean puree. As mentioned above, this batch will not get the same 13.33 g water, like most of the other batches.



Ingredients
- 1/6 package (45 g) Duncan Hines Keto Brownie Mix ($0.95)
- (44.2 g) Black beans, drained and rinsed ($0.14)

Nutrition Facts
------------------------------------------
Servings: 4
Calories: 64
------------------------------------------
Total Fat: 1.8g (2 %)
 Saturated Fat: 0.5g (3 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0.0g
 Monounsaturated Fat: 0.0g
Cholesterol: 0mg (0 %)
Sodium: 60mg (3 %)
Total Carbohydrate: 9.6g (3 %)
 Dietary Fiber: 3.0g (11 %)
 Sugar: 0.2g
Protein: 2.1g (4 %)
------------------------------------------
Vitamin B12: 0mcg (0 %)
Vitamin D: 0mcg (0 %)
Potassium: 126mg (3 %)
Calcium: 4mg (0 %)
Magnesium: 3mg (1 %)
Iron: 0.8mg (5 %)
------------------------------------------
 Glycemic Index: 46.2
Glycemic Load: 3.7
Mixing & Baking  
Each of the batches were measured and mixed in separate bowl. Note that the texture of the applesauce and banana batters was nearly identical to that of the control. However, the yogurt and sweet potato ones were noticably thicker, and the bean one was even thicker than that, almost like a sticky cookie dough. Left to right in the pan, we have - butter, applesauce, yogurt, banana, sweet potato, and black beans.


The batter was spooned into a liberally greased mini muffin pan, and baked at 350F for 14 minutes. A toothpick inserted in the center of each brownie came out mostly clean with some crumbs. Each different batter made 4 mini muffins, making 24 total.


The baked brownies were then left in the pan for about 20 minutes to cool, before being transferred to a wire rack using a butter knife to release them from the sides. Note that nearly none of them sticked. From left to right in the image below, we have - butter, applesauce, yogurt, banana, sweet potato, and black beans.



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. Below is our ranking from best (left) to worst (right). Ranking worst to best, we decided on - beans (worst), applesauce, banana, butter, yogurt, and sweet potato (best).


1. Butter & Eggs
These were the control brownie, and honestly they were pretty standard. Good taste; pretty much exactly what you'd expect from a brownie. They were slightly cakey, but had a good texture. They didn't really have anything going for them though, just kinda a mid brownie with a slight erythritol flavor. 6.5/10



2. Unsweetened Applesauce
As you can see from the photos, the applesauce ones caved in the center. This led to a very gooey but basically underdone center. The brownies collapsed due to the lack of structure; possibly due to the lack of eggs? However, the addition of the applesauce made the brownies a touch sweeter, and completely blocked any erythritol flavor. Just note that it will be less structural, and have a much softer texture. Thankfully, without wheat or eggs, they can be eaten totally raw, so there's no risk in underbaking. The texture was the main downside here. 6/10



3. Plain Nonfat Greek Yogurt
This was the only one that didn't make it out of the pan. It didn't stick, but 1 did break in half in the transfer. These also noticeably collapsed in the center, more than the applesauce. As for the taste and texture though, these tasted most similar to what you'd expect from a brownie, but just a touch less sweet; almost like a dark chocolate brownie. The yogurt adds a nice subtle flavor, and again the little erythritol taste is gone, which is good. This is so far the best all around replacement, as although it did collapse, it didn't feel underbaked like the applesauce. 7.5/10



4. Mashed Banana
The banana ones also collapsed in the center, just like the applesauce and yogurt ones before it. These brownies were gooey (slightly underdone like the applesauce), sweet, and delicious, but you could absolutely taste the banana. It was basically the exact same as the applesauce brownies, but with a banana flavor. While I really like the banana taste in brownies, you wouldn't be able to pass these off as brownies; these are instead banana brownies. This can either be a pro or a con depending on what you're in to, but do note that the banana taste is strong here. 6.5/10



5. Sweet Potato Puree
These ones were by far our favorites. Bith Vic and Cass though these ones were the yogurt, so they were surprised to hear the potatoes ranking at the top. They had the best texture; they were perfectly fudgy without being underbaked like the banana and applesauce. The texture was great, as they felt good in the mouth and didn't collapse in the center. For the taste, these were about as sweet as the applesauce ones, maybe slightly sweeter. The sweet potato ones basically were a combination of the pros of the butter (structure) and applesauce (taste). 9/10



6. Black Bean Puree
Last but unfortunately least, is the black beans. You could definitely taste a little hint of bean in these. These had a dense and fudgy interior, but were also slightly dry. They were the firmest, but also the least sweet. We could tell exactly which ones were the beans, even just by looking at them. A lot of recipes I saw that used beans in brownies instead drained and rinsed he beans, and substituted the water for coffee. I think that would yield better results, but as I made them, the beans were at the bottom. 4/10



Conclusion  
For my desired taste and texture, I found that replacing the butter with Sweet Potatoes to be the best option. The brownies were sweet and delicious, while being perfectly fudgy without being underbaked. Sweet potato puree is a breeze to make, just roast a whole potato until soft enough to blend into a puree. While not tested, butternut squash puree or canned pumpkin puree should work as great substitutes as well. One day, I would love to come back to this experiment, and make a full batch using sweet potatoes, to get a feel of how these brownies would be on a larger scale.

For making a full batch, I would replace the 6 tbsp (85 g) melted butter with 6 tbsp (95.63 g) sweet potato puree (or pumpkin or butternut squash). Since this is a full batch, and you would not need to divide the eggs weird, you can choose to either use the standard 2 large eggs, or replace the eggs with 1/2 cup (127.5 g) sweet potato puree. If you do decide to replace the eggs with sweet potato, then you will need a total of 6 tbsp (95.63 g) + 1/2 cup (127.5 g) = 14 tbsp (223.13 g) sweet potato puree. Keep the 1/3 cup (80 g) water constant, or swap the water for unsweetened vanilla almond milk. Bake according to packaging in a greased 8" pan (24-28 min at 350F), and slice into 16 brownies.

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.

Ingredients  
Below are the full ingredients list and nutrition facts for a standard batch of Duncan Hines Keto Boxed Brownies, made healthier using Sweet Potatoes. You can also use an additional 1/2 cup (127.5 g) mashed sweet potato in replace of the 2 eggs if you like.

Ingredients
- 10 oz box (284 g) Duncan Hines Keto Brownie Mix ($6.00)
- 6 tbsp (96 g) Sweet potato puree ($0.33)
- 2 eggs (101 g) Egg ($0.24)
- 1/3 cup (80 g) Unsweetened vanilla almond milk ($0.10)

Nutrition Facts  
Below are the nutrition facts for 16 brownies for a standard batch of Duncan Hines Keto Boxed Brownies, made healthier using Sweet Potatoes. For reference, the standard butter batch of keto brownies cut into 16 would be 130 calories each with 7.4g fat (with essentially 0g sugar), whereas standard Duncan Hines brownies cut into 16 pieces has 215 calories with 12g fat and 19g sugar.

Nutrition Facts
------------------------------------------
Servings: 16
Calories: 98
------------------------------------------
Total Fat: 3.3g (4 %)
 Saturated Fat: 1.0g (5 %)
 Trans Fat: 0g
 Polyunsaturated Fat: 0.1g
 Monounsaturated Fat: 0.3g
Cholesterol: 26mg (9 %)
Sodium: 56mg (2 %)
Total Carbohydrate: 13.5g (5 %)
 Dietary Fiber: 3.9g (14 %)
 Sugar: 0.3g
Protein: 3.2g (6 %)
------------------------------------------
Vitamin B12: 0.1mcg (2 %)
Vitamin D: 0.2mcg (1 %)
Potassium: 174mg (4 %)
Calcium: 14mg (1 %)
Magnesium: 2mg (1 %)
Iron: 1.3mg (7 %)
------------------------------------------
 Glycemic Index: 55.4
Glycemic Load: 6.2
Other Substitutions  
Below is a list of other substitutions I found while researching for this post. I did not test any of these, so maybe this is worth a part 2 at some point.

1. Natural Peanut Butter
  1 egg = 1/4 cup (64 g) peanut butter
  1 cup butter = 1 cup (256 g) peanut butter
2. Mashed Avocado
  1 egg = 1/4 cup (57.5 g) mashed avocado
  1 cup butter = 1 cup (230 g) mashed avocado
3. Cornstarch + Water
  1 egg = 1 tbsp (8 g) cornstarch + 3 tbsp (45 g) water
  1 cup butter = 1 cup (128 g) cornstarch + 1/2 cup (120 g) water
4. Diet Coke
  1 egg = 1/4 cup (60 g) diet coke
  1 cup butter = 1 cup (240 g) diet coke
5. Buttermilk
  1 egg = 1/4 cup (61 g) buttermilk
  1 cup butter = 1 cup (244 g) buttermilk
6. Roasted Beets
  1 egg = 1/4 cup (60 g) pureed beets
  1 cup butter = 1 cup (240 g) pureed beets

Update (Apr-23-2023)
I ran a similar experiment, making a half batch each of canola oil brownies and sweet potato brownies, using Duncan Hines Dark Chocolate Fudge brownies as the base. You can read the results of my Sweet Potato Boxed Brownies experiment. Spoiler alert: the results aren't as positive.

Sources  
1. Use Randall Pinto Beans And Randall Great Northern Beans In Creative Recipe Swaps
2. Replacing Butter with Beans
3. Why Use (Black) Beans in Brownies?
4. Looking for a Substitute for Eggs in Cooking or Baking
5. What If I Made Boxed Brownies Without Eggs? An Experiment.
6. The Best Substitutes For Vegetable Oil In Brownies
7. I Taste-Tested 3 Oil Substitutes for Brownies and This Is What Happened
8. Egg Substitutes for Baking Ultimate Guide for 2024
9. 8 Surprising Oil Substitutions For Lighter, Healthier Brownies