Mochi Sourdough Milk Bread

For my first bake back home in Toronto I wanted to experiment with my sweet rice flour (glutinous rice flour which is gluten free of course).  I had read in Serious Eats the following which I found quite informative and interesting.

“ …the presence of a scald makes a bread far more resistant to staling than dough made without one. More accurately known as starch retrogradation, staling is the reversal of gelation, where the water in the starches gets pulled out of them, causing the starches to crystallize and harden. The more water in a bread, the longer it takes for the starches to retrograde. (Stale bread seems dry, but it isn’t necessarily, at least not initially. The starches have crystallized in a stale bread, but the water may still be hanging around nearby; this is the reason that toasting stale bread can restore some of its original tenderness.)

Which brings me to sweet rice flour. As I mentioned above, starch is made up of two types of molecules: amylose and amylopectin. Amylose molecules are long chains of glucose linked together, with only a few branches hanging off the central chain here and there. Crystals form most readily when the molecules in question can stack together neatly. Because amylose molecules are mostly straight chains, they are especially prone to crystallizing as food cools. (This is why long-grain rice, which contains around 20% amylose, becomes especially hard and brittle when refrigerated.) Meanwhile, amylopectin molecules are highlybranched, making them unable to stack together and crystallize as efficiently.

The starches in wheat flour are 28% amylose and 72% amylopectin, which makes it a less-than-perfect choice for a flour scald—one of the big benefits of using a flour scald is it slows staling, but wheat flour has a healthy dose of staling-prone amylose. Sweet rice flour, on the other hand, is nearly 100% amylopectin, making it ideal for using in a scald—especially if you want the bread to stay soft for as long as possible.

Another advantage to using sweet rice flour instead of wheat flour in a scald: It’s much easier to make. The standard tangzhong method has bakers combine flour and cold water (usually in a 1:4 ratio) until it is uniform. Bakers then cook the mixture on the stovetop until it gels. While this is an effective technique, it is—simply put—a pain in the ass, as it’s challenging to get the sticky paste out of the pan and into the dough completely.

I use a technique similar to the yudane method, where I pour boiling milk over glutinous rice flour and sugar and whisk the mixture until it thickens to a pudding-like consistency. Unlike the traditional yudane method, though, I use much more flour than is typical—20% of the total weight compared to the 5 to 10% most shokupan recipes contain—and instead of bread flour, I use sweet rice flour for all the reasons mentioned above. I also use a different ratio of 1 part flour to 3 parts liquid. This approach produces a smooth, thick gel easily and quickly, with no lumps in sight.”

For my bake I wanted to try using the sweet rice flour in the tangzhong but prepared as I usually do with a 1:2 ratio to the milk.  Unfortunately I made an error with hydration and the resulting dough was much higher in hydration than I wanted and thus I couldn’t shape it with the four lobes.  Also, the rising bread had a blow out on one side above the rim of the pan.  This could have been avoided by doing a score which I seldom do when I bake enriched doughs that are egg washed.  

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For one 9x4x4” Pullman pan loaf.

Instructions

Levain

Mix the levain ingredients in a jar or pyrex container with space for at least 300% growth. 

Press down with your knuckles or silicone spatula to create a uniform surface and to push out air.

At a temperature of 76-78ºF, it typically takes up to 10-12 hours for this sweet stiff levain to be at peak.  For my starter I typically see 3-3.5 times increase in size at peak.  The levain will smell sweet with only a mild tang.

Tangzhong 

In a sauce pan set on medium heat, stir the milk and glutinous rice flour until blended. Then cook for several minutes until well thickened, stirring regularly with a spoon or heat-resistant spatula. Let cool in the pan or, for faster results, in a new bowl.  Theoretically it should reach 65ºC (149ºF) but I don’t find I need to measure the temperature as the tangzhong gelatinizes at this temperature.  You can prepare this the night before and refrigerate it, ensure that it is covered to prevent it from drying out.

If you plan on using a stand mixer to mix this dough, set up a Bain Marie and use your stand mixer’s bowl to prepare the tangzhong.

Dough

In the bowl of a stand mixer, add the milk (consider holding back 10 g of milk and adding later if this is the first time you’re making this), egg, tangzhong, salt, sugar and levain.  Mix and then break up the levain into many smaller pieces.  Next add the flour.  I like to use my spatula to mix until there aren’t many dry areas.  Allow the flour to hydrate (fermentolyse) for 20-30 minutes.  Mix on low speed and then medium speed until moderate gluten development this may take 5-10 mins.  You may want to scrape the sides of the bowl during the first 5 minutes of mixing.  Next add room temperature butter one pat at a time.  The dough may come apart, be patient, continue to mix until it comes together before adding in more butter.  Again, knead until well incorporated.  You will want to check gluten development by windowpane during this time and stop mixing when you get a good windowpane.  You should be able to pull a good windowpane, not quite as good as a white flour because the bran will interrupt the windowpane somewhat.  Add the seeds, then mix again until they are well distributed.

On the counter, shape the dough into a tight ball, cover in the bowl and ferment for 2 - 4 hours at 82ºF.  There should be some rise visible at this stage.

You can next place the dough into the fridge to chill the dough for about 1.5 hours, this makes rolling the dough easier to shape.  Remember, if you do so the final proof will take longer.  Alternatively, you can do a cold retard in the fridge overnight, however, you may find that this increases the tang in your bread.

Prepare your pans by greasing them with butter or line with parchment paper.  

Lightly oil the top of the dough. Scrape the dough out onto a clean counter top and divide it into four. I like to weigh them to have equal sized lobes. Shape each tightly into a boule, allow to rest 5 mins. Using an oiled rolling pin roll each ball out and then letterfold. Turn 90* and using a rolling pin roll each out to at least 8”. Letterfold again from the sides so you have a long narrow dough. Then using a rolling pin, roll flatter but keeping the dough relatively narrow.  The reason to do this extra letterfold is that the shorter fatter rolls when placed in the pan will not touch the sides of the pan.  This allows the swirled ends to rise during final proof, this is only done for appearance sake and is not necessary.  Next roll each into a tight roll with some tension. Arrange the rolls of dough inside your lined pan alternating the direction of the swirls. This should allow a greater rise during proof and in the oven.

Cover and let proof for  4-6 hours at a warm temperature.  I proof at 82°F.  You will need longer than 4-6 hours if you chilled your dough for shaping. I proof until the top of the dough comes to within 1 cm of the top edge of the pan.

Preheat the oven to 350F and brush the dough with the egg-milk wash.  Just prior to baking brush with the egg-milk wash again.

Bake the loaves for 50 minutes or until the internal temperature is at least 190ºF, rotating as needed to get even browning. Shield your loaf if it gets brown early in the baking process. After 50 mins remove the bread from the pan and bake a further 10 mins by placing the loaf directly in the oven on the rack with the oven turned down to 325ºF

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This bread is exceptionally soft and the next day after slicing it was still as fresh textured as the first.  Now whether this is completely related to the much higher hydration than I usually use or the sweet rice flour I don’t know as both are likely to have affected this.  I’ll have to do another bake with the hydration corrected.  However, the tangzhong was easy to incorporate and easy to make and it was a good use of the sweet rice flour that I already had in my cupboard.  I will definitely make the updated version of the bread.