Sourdough Purple Sweet Potato Milk Bread

Meet my latest sourdough milk bread experiment: purple sweet potato milk bread. 🍠💜 It’s soft, fluffy, slightly sweet, and naturally purple thanks to mashed purple sweet potato. And yes, getting it there was a whole journey…

Okay, I thought my sourdough pumpkin milk bread made me work really hard, but this one was even worse… with 11 test loaves!!! You know who’s not unhappy about it? My coworkers and friends! They got to try all the “failed” loaves, even those ones were still tasty, toasted with butter. 😋

Key ingredients

🍠 Needless to say, purple sweet potato is key in this recipe. I’ve used Okinawan sweet potato as well as Stokes purple sweet potato successfully in this recipe. Okinawan sweet potatoes are a bit harder to find but you may come across fresh ones at Japanese grocery stores. I like that it has a bit more moisture than Stokes. But either works beautifully.

However, I want to be very clear that this is NOT UBE. Fresh ube would be harder to find yet. There are frozen ube and ube powder which I have not tested with, so this recipe will not work with ube.

Sample baking schedule

This purple sweet potato milk bread is best as a same day bake once you start the dough. There are a couple things you still need to prepare the day before: your starter and your potato. The schedule below accounts for that. Remember that the timeline is my best estimate to give you an idea what to consider when you bake this loaf. Time will vary depending on the temperature the day you’re baking, how strong your starter is, etc. 

You can split this bake into 2 days if you run out of time while preparing the dough and need to add the cold fermentation step (after bulk fermentation finishes). However, whenever I refrigerate this dough, I notice it doesn’t rise as well the next day and end up with a small line of dense section at the bottom of the loaf. Still tastes amazing, but that stumped me for so long until I tested baking it the same day.

Let’s make sourdough purple sweet potato bread!

Before you start, make sure you cook your sweet potato. You can steam or bake it. I prefer baking it because it caramelizes the sugar in the sweet potato giving it more flavor IMO. I don’t recommend microwaving as it dries out the potato and makes it really hard to mash.

1. Make purple starter (night before)

This starter is purely for visual. You can use a regular sourdough starter to make this loaf with some small modifications. If you are planning to use a regular starter, feed it as you normally would, use 100 grams of starter in the bread dough and increase the amount of purple sweet potato in the dough from 100 grams to 120 grams.

NOTE: Make sure you have an active regular sourdough starter before making this purple starter.

2. Prepare your liquid

It may be a bit difficult to mix the purple sweet potato with the milk mixture. If the potato is too chunky you can use an immersion blender to blend the mixture smooth.

3. “Autolyse”

Mix together flour, salt and the cooled purple sweet potato mixture, cover and let this rest for 15-20 minutes.

NOTE: This is not a true autolyse since we are adding a bunch of ingredients to the mixture. However, I think this step still helps with dough strength and extensibility since this dough can break easily during stretch-and-fold due to the potato in the dough.

4. Knead the dough

Add all of the purple sweet potato sourdough starter to the “autolysed” dough and knead with the dough hook for 20 minutes.

NOTE: This is also technically the start of bulk fermentation, as soon as you mix the starter into the dough.

5. Continue bulk fermentation

Scrape the dough out and shape it into a ball and place it back into the oiled bowl to continue bulk fermentation.

6. Stretches and folds

During bulk fermentation, you will perform 3 sets of stretch-and-fold to add strength to your dough at 45-minute intervals. Once you are finish with your last set, cover and let the dough finish bulk fermentation at room temp.

NOTE: You will notice the dough rising some during this step. That’s okay, don’t worry about deflating it. You will also notice it gets harder to pull and stretch during set 2 and 3. Don’t force it, you want to build strength but don’t want to break the gluten strands.

7. Divide the dough

Cut the dough into 3 equal portions. Roll them into smooth balls, cover and let rest for 10-15 minutes to allow the gluten to relax before shaping.

NOTE: This dough is not very sticky at all but I love using a silicone baking mat and vinyl gloves to keep it from sticking further.

8. Shape into logs

Shape each ball into a log like so and place them into your loaf pan.

9. Proof the dough

Proof the dough for about 5 hours. The dough is ready when it is very puffy, has risen well above the rim of the loaf pan, and a gentle press leaves an indentation that slowly springs back (but not immediately).

NOTE: Proofing time is highly dependent on temperature so make sure to pay attention to visual cues.

10. Bake

Brush milk generously over the surface of your dough and bake at 400°F (205°C) for 7 minutes, then reduce the temperature to 350°F (180°C) and bake for another 21-23 minutes. You want the internal temperature of your bread to reach 190 – 200°F. Let cool completely before cutting into it.

NOTE: This loaf takes a couple mins longer to reach the correct internal temp compared to my original milk bread and other loaves.

Storage

• Room temperature: you can store your sourdough purple sweet potato milk bread at room temperature for a couple days. Only slice off whatever you’re planning to eat to keep the moisture within the loaf. Store the bread in a ziploc bag. Since this loaf is homemade with no preservatives, I would keep it refrigerated to prevent spoiling if it lasts longer than 2-3 days or if the weather is particularly hot and humid. I lost 2 good loaves to mold during a heat wave we had in just 2 days.
• Refrigerator: you can also keep your bread in the fridge for a couple weeks. Again, only slice what you need and keep it in a ziploc bag. It does dry out a bit the longer you store it, but will get softer in the toaster with cripsy exterior.
• Freezer: for the freezer, I recommend slicing and then freezing. This way you can defrost only what you need when you need. Or freeze and thaw the whole loaf. Your bread should last up to 3 months. To preserve the flavor, wrap the loaf in foil as well as plastic and then store in a freezer bag.

This loaf is great for toast, I’ve had it with just salted butter or cream cheese, no need for jam since it’s already a bit sweet. But I’ve also had it with purple sweet potato spread, a sort of jam made with purple sweet potato, that was delicious. I haven’t tried making french toast with it but I think it will be great a french toast too.

Sourdough Purple Sweet Potato Milk Bread

By: Trang Doan

Meet my latest sourdough milk bread experiment: purple sweet potato milk bread. 🍠💜 It’s soft, fluffy, slightly sweet, and naturally purple thanks to mashed purple sweet potato.

Servings : 12 slices

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Prep Time : 10 hours hours

Cook Time : 30 minutes minutes

Total Time : 10 hours hours 30 minutes minutes

Equipment

• Kitchen scale
• Thermometer
• Stand Mixer
• Saucepan
• Spatulas
• Bowl scraper
• 1-pound loaf pan (8.5” x 4.5”)
• Silicone mat
• Vinyl gloves

Ingredients 

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Purple sweet potato sourdough starter

• 10 grams active sourdough starter
• 20 grams purple sweet potato mashed
• 45 grams bottled water
• 45 grams bread flour

Bread dough

• 130 grams milk
• 50 grams brown sugar
• 57 grams unsalted butter sliced into thin pats
• 100 grams purple sweet potato mashed
• 280 grams bread flour
• 6 grams kosher salt
• All of the purple sweet potato starter
• Neutral oil for dough handling
• Extra milk or egg wash

Cook Mode(Prevent your screen from going dark)

Instructions

Day 1

• Prepare the purple sweet potato – Bake or steam your sweet potato until soft, a fork should easily go through the middle. To bake: poke the potato with the tip of a knife a few times, wrap it in foil, and bake for 30-45 mins at 375°F. To steam: place the potato in your steamer with water in the bottom, bring the water to a boil then lower the heat to keep it simmering, and steam for 10-20 mins. Let cool before using.
• Make purple sweet potato starter – Mix all the ingredients for your sweet potato starter together in the evening and it should be ready to use within 12 hours.
  10 grams active sourdough starter, 20 grams purple sweet potato, 45 grams bottled water, 45 grams bread flour

Day 2

• Prepare the liquid (8 am) – Heat the milk with brown sugar in a small saucepan over medium heat, stirring constantly, until the milk is simmering and the sugar has fully dissolved. Turn off the heat, add the sliced butter to the hot milk mixture, and stir until completely melted. Add to a stand mixer bowl and stir in the mashed purple sweet potato. Let it cool. If the potato is hard to mash, you can use an immersion blender to blend the potato with the milk mixture until smooth.
  130 grams milk, 50 grams brown sugar, 57 grams unsalted butter, 100 grams purple sweet potato
• “Autolyse” (8:15 am) – Make sure your liquid mixture is between 80 – 90°F (27 – 32°C), add flour and salt to the cooled liquid mixture. Use a spatula to mix until all the liquid is absorbed. Cover and let rest for 15 – 20 minutes.
  280 grams bread flour, 6 grams kosher salt
• Knead the dough (8:35 am) – Add all of the purple sweet potato starter to the “autolysed” dough. Knead with the dough hook on speed 2 for 20 minutes.
  All of the purple sweet potato starter
• Continue bulk fermentation (9 am) – Oil your hands, a bowl scraper, and your clean countertop. You can use gloves and the silicone mat on your surface to further help prevent sticking. Scrape the dough out and shape it into a ball on the oiled surface. Lightly oil the mixing bowl, then return the dough to the bowl. Cover and place in a warm spot. You will perform 2 – 3 sets of stretch and fold at 45-minute intervals. Set a timer for 45 minutes.
  Neutral oil for dough handling
• Stretch and fold #1 (9:45 am) – With oiled hands, lift the dough from the center. It will stretch as you lift it up and out of the bowl. If it’s sticky, use your bowl scraper to help release it. Stretch the dough into a long strip and fold in thirds like you’re folding a letter. Turn it 90 degrees, stretch it out into a long strip again and fold in thirds. Place it seam-side down back into the mixing bowl, cover, and set the timer for another 45 minutes.
• Stretch and fold #2 (10:30 am) – Repeat the same process. At minimum, complete 2 sets if short on time.
• Stretch and fold #3 (11:15 am) – Repeat one final set. The dough should feel stronger and more elastic. It should also have risen a bit. Cover and let it finish bulk fermentation at room temp for another 1-2 hours.
• Divide (12:45 pm) – Using your bowl scraper, scrape the dough onto a lightly floured surface and divide into 3 portions, approximately 240 grams each. Roll each into a smooth ball. Cover and let rest for about 10-15 minutes.
• Shape (1:00 pm) – Take each dough ball, smooth side down, flatten with your hand or roll into a rectangle, fold into thirds like a letter. Flatten again and allow it to stretch lengthwise, but keep the width slightly narrower than your loaf pan. Roll up into a log and place into the loaf pan.
• Proof (1:15 pm) – Proof your dough in a warm spot for about 5 hours. I typically use a 15-quart storage bin as my proofing box. You can also proof your dough in the oven with the light turned on and place a pan of hot water at the bottom of the oven to add humidity. The dough is ready when it is very puffy, has risen well above the rim of the loaf pan, and a gentle press leaves an indentation that slowly springs back (but not immediately).
• Preheat the oven (5:30 pm) – Toward the end of proofing, preheat the oven to 400°F (205°C) for at least 30 minutes. If proofing in the oven, remove the dough before preheating.
• Bake (6:00 pm) – Brush the top of the loaf and any exposed sides with extra milk or egg wash. Bake at 400°F (205°C) for 7 minutes, then reduce the temperature to 350°F (180°C) and bake for another 21-23 minutes. The top should be golden brown and the internal temperature should reach 190 – 200°F.
  Extra milk or egg wash
• Cool – Let your bread cool in the pan on a wire rack until just warm to the touch before removing it from the pan. Cool completely before slicing.

Notes

• The purple sweet potato added to the starter is purely for visual. You can certainly use your regular sourdough starter for this loaf, just add the extra 20 grams of purple sweet potato you would have used in the starter to the dough instead and use 100 grams of sourdough starter for your bread.
• Rising time and proofing time are highly dependent on temperature. So make sure you watch your dough and not the clock, use my timeline as a general gauge but pay attention to visual cues to ensure you don’t under or over proof your bread.
• I prefer using oil to prevent dough from sticking to my hand instead of extra flour to avoid adding too much flour to the dough risking a drier loaf.
• The timeline is a suggestion, feel free to modify it to fit your schedule.

Nutrition

Calories: 164kcal | Carbohydrates: 26g | Protein: 4g | Fat: 5g | Saturated Fat: 3g | Polyunsaturated Fat: 0.4g | Monounsaturated Fat: 1g | Trans Fat: 0.2g | Cholesterol: 12mg | Sodium: 206mg | Potassium: 84mg | Fiber: 1g | Sugar: 5g | Vitamin A: 1555IU | Vitamin C: 0.2mg | Calcium: 25mg | Iron: 0.3mg

Nutrition information is automatically calculated, so should only be used as an approximation.

So… was this bake worth the ferment?Let us know by rating this recipe.