A celebration of berries part II: "Black" Blueberry Bagels

I had a bunch of fresh blueberries in the fridge and a bag of KA Sir Lancelot high-gluten flour that had been sitting in the pantry for too long, so naturally, I decided to try making blueberry bagels. There were a few considerations beforehand:

-would the blueberry flavor be concentrated enough from just fresh blueberries?

-would I be able to knead whole berries into the dough, or would I have to find some other method of incorporation?

-how should I adapt my usual go-to bagel formula?

On the first point, I decided I would go ahead with the experiment and find out by tasting the product. Regarding the second point, in all my online research, I'd never seen a blueberry bagel with fresh whole berries kneaded in (they would probably explode and leave a mess), which led me to the decision that I would cook the berries down into a sauce, puree the sauce, and strain it to yield a smooth liquid, which I would use to replace part of the liquid in the formula. Below on the left is the blueberry sauce after cooking. On the right is the strained blueberry puree diluted with water (how much water? see below).

Finally, to my third initial question: how to adapt the formula to account for solid matter in the blueberry puree? First, I decided to use SAF Gold label osmotolerant yeast instead of regular instant yeast in case the amount of sugar in the puree was too high.

I use Peter Reinhart's bagel formula in the bread baker's apprentice, which is about 57% hydration. Not knowing what percentage of the blueberry puree was water, I wasn't sure how to adjust the amount of liquid, so I played it by ear. I just estimated that there would have to be 2 extra ounces of water than the formula calls for to compensate for the blueberry. I planned to adjust the flour later, if necessary, depending on how the dough felt.

All the liquid in the BBA formula is incorporated in the sponge step, which yielded a lovely, lumpy, purple batter:

The sponge was allowed to ferment until doubled in bulk, which took about 4 hours.

Once the other ingredients were incorporated, it seemed like the dough wasn't stiff enough, so I ended up adding another 2 ounces of high gluten flour. In my bagel experiences in the past, too slack a dough caused the bagels to become floppy in the boiling step. This brought the calculated hydration level to about 59%, but given how the dough felt, it was probably slightly lower. Here is what the dough looked like:

This brought the calculated hydration level to about 59%, but given how the dough felt, it was probably slightly lower. The final recipe was as follows (adapted from p.119 of Peter Reinhart's Bread Baker's Apprentice)

Sponge:

1 tsp instant yeast

18 oz unbleached high gluten flour

22 oz total of blueberry puree and water (use all the puree and add enough water to bring it up to the total)

Dough:

1/2 tsp osmotolerant yeast

19 oz unbleached high gluten flour

0.7 oz salt

1 Tbsp barley malt syrup

Immediately after kneading to the windowpane stage, as Mr. Reinhart instructs, I divided the dough into 4 oz pieces and shaped them into rounds. The rounds were allowed to rest for 10 minutes. Afterward, I rolled each one out into a flat somewhat rectangular sheet and rolled them up tightly into logs. 

After another ten minutes of resting under damp paper towels (the dough dried up on the surface very quickly without them), I extended the logs into long snakes, looped them around my fingers, and rolled the overlapping ends to seal the bagel into the "O" shape. I found that for the best result, the overlapping area should span at least the width of your four fingers. I had to supplement this rolling method with some pinching to seal the ends securely.

Then came an overnight retardation in the fridge. In the morning, the bagels had puffed up slightly, but not dramatically:

I preheated the oven to 450 instead of 500 as instructed in the book to account for the extra sugar content in the dough. Next I prepared a boiling solution consisting of:

8 cups of water

2 Tbsp baking soda

1 Tbsp barley malt syrup

Once the solution came up to a gentle boil (more than a simmer but less than a rolling, witches' brew boil) I popped the bagels in for 2 minutes per side. I should have expected this, but I was surprised to find that some chemical reaction between the baking soda solution and the blueberries caused the purple bagels to turn almost black! Below you can see the contrast between the boiled bagels and the unboiled ones. I was hoping that the baking soda was indeed the reason behind the color change, and that the inside would stay pleasantly purple.

After baking for about 15 minutes, with a couple rotations of the sheet pans for evenness of browning, they came out dark greyish purplish brownish black (maybe there's a name for this shade in the Sherwin-Williams catalogue?). When I sliced them open, I was relieved to find that the lovely purple color had not disappeared entirely. The crusts actually provided a nice contrast to the interior color.

Back to the first initial question: was there enough blueberry flavor? I wouldn't say the flavor was overtly of blueberry. The dough had a gentle sweetness and a definite blueberry fragrance, but the sensation of the fruit was mostly olfactory. After savoring a bite for a little bit, the blueberry begins to come through. The floral nature of the fruit complements the malt flavor of the bagel nicely. They're delicious with some fruity cream cheese. The crust color was at first discouraging, but now I kind of like the idea of slicing one open to find a bright surprise on the inside.