The Science Behind… mashed potato bread and experimenting with starch gelatinization

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I imagine some of you are sick by now of my mentioning how I messed up a recipe by scalding the flour, thereby creating a bread with a completely different texture than usual.

The mistake opened up a whole new world for me of creating breads that were soft and light without using any fat!

After a little research, I learned that by adding boiling hot water to flour, I had gelatinized the starches in the flour.  This caused the sugar molecules to rapidly absorb the water, then burst- resulting in a gelatin-like consistency that resisted the strong net of gluten formation.

But scalded flour isn’t the only way to get the benefits of starch in your bread.  Mashed potatoes, or water from cooking potatoes or rice also have starch, and is a great way to use up a waste product that you might otherwise have thrown away!

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In this post, I will discuss:

  1. What is starch?
  2. What does starch do in bread?
  3. How can I add starch to a recipe?

Here we go!

  1. What is starch?   Starches are complex carbohydrates (sugars) which occur in wheat and many other plants that rely on photosynthesis. Any sugars that are not used by the plant for energy are stored up in polysaccaride chains.  The starch is stored in the endosperm part of the plant.

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Long ago, people discovered that different plant starches were useful for thickening all kinds of dishes.  Each has its own unique characteristics and are useful for different preparations.  Some examples of starches we commonly use today are cornstarch, arrowroot starch, cassava/tapioca starch, and flour.

2. What does starch do to bread?  When we talk about this, we need to distinguish between wheat starch and potato (or other) kinds of starch.

According to the website The Science of Bread Making, “Studies have shown that wheat starch is very unique and compared to other starches (rice, potato, corn) contributes desirable characteristics to bread.It does not disintegrate at high temperatures like other starches, but remains flexible during gelatinization so that the bread can spring up in the oven. During baking wheat starch absorbs more water, taking enough water away from the gluten strands to make them rigid so that the loaf of bread will stand firm without collapsing when removed from the oven. (Pyler, 1988).

Unlike wheat starch, most other starches have low or no gluten.  So they add softness from gelatinization without also adding a rubbery, rigid texture from extra gluten.

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3. How can I add starch to a recipe?

Since the focus of this post is on mashed potatoes, I’ll use potatoes as an example.  Potatoes are about 75% water, however, once they are cooked they are unlikely to absorb any more water (they might even give off some of their water!).  Try adding up to 1/5 of the total weight of flour as mashed potatoes without making any other changes.

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Potato water can be used anywhere you would otherwise use water.   If you decide to add dried potato flakes, you will want to account for any additional absorption they will do.  Test them out and see if you need to add any additional water.

So, that’s it!  Starch and gelatinization in a nutshell.  If you have any other questions, please let me know in the comments.

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Sources:

http://www.thescienceofbreadmaking.com/carbohydrates.html

On the Many Uses of Gelatinized Starch

A Starch is a Starch

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