The Effect of Sponge Age on Sourdough Characteristics (Update #10)

Look, I promise this is the last time this summer that I will be posting about bread and how cool it is. If the posts have been too much I am sorry. On the other hand, if you’ve been enjoying reading about my floured adventure then this is a bittersweet (or maybe…sour) moment. I know it is for me. Over the past week I have made a batch of sourdough every day for five days in order to see how aging the sourdough sponge mixture for different periods of time affects the final product. The results were conclusive and encouraging taste-wise (which is totally subjective and just going based off of what my family and I thought) and relatively inconclusive in terms of quantitative data that I took from the form of the loaves themselves. From this pattern we know that the age of a sourdough sponge doesn’t affect the physical properties of a loaf in any meaningful way, but the taste is extremely variable, going from essentially tasting like plain white bread (trial 1) to tasting very tangy and delicious (trial 5).

A sourdoughy kitchen

A sourdoughy kitchen ūüôā¬†

So, I should probably start with what the heck a “sourdough sponge” is. When I first saw the words next to one another I imagined an airy sponge cake with a hint of fermented yeast flavor (yuck). It turns out that, in the world of bread, a “sponge” is a mixture of flour, water, and another ingredient (in this case sourdough starter) that is made¬†days before one plans to bake so that it can sit out and develop deeper flavors. The recipe that I used was extremely simple, requiring only flour, water, salt, yeast, and starter. The most mystical of these five ingredients, at least to me, was the sourdough starter itself. So, at the beginning of the summer I whipped together my own starter, making use of flour, water, and time. Leaving a starter out in the open air for a couple days lets good bacteria get into the¬†mixture and starts the fermentation process that gives a loaf of sourdough its textbook tang. Check out this website for a resource on all things cultured¬†–>¬†

A sourdough sponge, post-aging

A sourdough sponge, post-aging

The five trials of my experiment represented five different time horizons for my sourdough sponge. Trial 1 was made after no aging, meaning that I simply put all the components together in a bowl and then continued on with the recipe. Trial 2 was made after leaving the sponge mixture out for one day. Trial 3 was aged for two days, trial 4 for three days, and trial 5 for four days. I was worried that the sponge would go bad in the later trials, and I knew that the first trials (especially #1) would not taste sour enough to even warrant being called “sourdough.” Therefore, my hypothesis was that, if the sponge was left to age for two days, then the most balanced and delicious sourdough flavor would be produced.

To test my prediction, I began whipping together some breads! After the sponge is aged to one’s liking, making a sourdough loaf is very easy. One simply must combine yeast, salt, and flour with the sponge and then kneed the mixture before splitting the dough into two pieces and letting it rise for two hours. Then the two loaves are ready to be baked in a 425 degree F oven for 20 minutes. The oven temperature should then be reduced to 350 degrees F, and the breads should be¬†left to bake for another 20 minutes.

Wrastlin' up some dough (yeehaw)

Wrastlin’ up some dough (yeehaw)

The results of my experiment were straightforward, yet unexpected. The longer the sponge was left out, the more tangy and tasty the final product became. The only reason why I wasn’t expecting this result was because I thought that the sponges left out for longer than two days would go bad. Bad bacteria on a sourdough starter/sponge can be any number of colors (the most noticeable of which is pink!), and a good rule of thumb is that if there is any coloration on your sourdough ingredients besides the pale white of the flour and water, then the starter should be thrown out. Luckily, even the 5th trial of my sponges (the one that was left out for four days) was still good by the time I peaked underneath the wax paper.¬†Therefore, based on my findings¬†I would recommend that a sourdough sponge should be left out at room temperature for four days in order to garner the best results when baking. A four-day sponge produces loaves with a noticeable sour flavor that will please even the most hardcore sourdough addict. If you are pressed for time, the soonest that a strong¬†tangy taste will form in your sponge is after two days, so do yourself a favor and wait that long before baking your beautiful loaves. Of course, the conditions of my kitchen are different from yours, so play around with your sponge’s age and do what you like best. Just make sure that if you push the boundaries of how long you leave your mixtures out, that you are also ready to throw out any sponge that has grown colorful bacteria.

And with that, friends, I leave you to live out your last few days of summer in peace. I know that sometimes this last week before going back to school can feel isolating, with the summer blues setting in thanks to the prospect of essays to write and the fact that many friends are already away working, traveling, or studying. If this is the case for you, at anytime in your life, I would encourage you to try baking some bread. It is an extremely therapeutic and cathartic experience, and communing with your food is a surefire way to make you feel energized and grounded. At least in my opinion. See you soon.