by Les Saidel - December, 2010
For all those who bake their own challahs at home, how do you know when the challahs have risen enough and are ready to go into the oven to bake?
Using rising times given in recipes or books are often misleading because factors like yeast quality, weather, temperature etc. can affect the rising time of the dough. You need a failsafe method that can adjust to any environmental condition.
The answer is simple - prod your challah. At various intervals in the rising process (after you have shaped the challahs), give the challah a light "prod" with your finger.
If the indentation that remains immediately springs back and disappears completely, the challah needs to rise some more. If the indentation remains and does not spring back at all, the challah has over-risen and may deflate when you bake it. If the indentation mostly springs back but a trace of it still remains - your challah is ready to go into the oven.
Getting your challahs into the oven exactly when they are ready is one of the secrets to puffed up, beautiful looking challahs. Challahs whose crust comes out cracked or "exploded" were probably baked too early, before they had risen enough. Challahs that are flat, deflated and spread out, probably rose for too long before they were baked.
So next time you bake a challah, give it the "prod test".
That was the how, now for the why, the method behind the madness.
The reason a dough rises is because of three major factors - gluten, yeast and carbon dioxide.
Wheat flour contains two proteins (glutenin and gliadin) that when combined create a complex protein called gluten. To create this complex protein the two proteins gliadin and glutenin need to be combined in a specific way - with friction and layering. This is acheived by the kneading process. Until you knead dough vigourously there will be very little gluten. The kneading process, abrading and layering, creates a gluten structure which is very similar to a spiders web, containing millions of microscopic strands of proteins.
The presence of yeast in the dough is the next factor that makes the dough rise. Yeast is a living organism that metabolises (i.e it eats and breathes). The food of the yeast cells is glucose. Glucose is supplied after the complex sugars in flour (starch etc.) are broken down by enzymes. The yeast feed on the glucose and cause a chemical reaction of which a byproduct is carbon dioxide (CO2). As the yeast feed and multiply, more CO2 is produced. If the yeast were fermenting in a bowl of sugar water, you would see the bubbles of CO2 gas forming on the surface. These bubbles expand and then pop, releasing the CO2 into the air. That's a bowl of water. The expanding CO2 bubbles in a dough with the millions strands of gluten, have nowhere to go, they are trapped by this spiders web of protein. So they just keep getting bigger and bigger and push and stretch the gluten strands around them. This is what gives the rising effect of the dough, it is like a huge balloon with millions of tiny bubbles.
To understand why the "prod test" works, we need to understand one more attribute of the dough - it's tensile strength. The two proteins gliadin and glutenin that form the gluten structure each contribute a specific attribute to the dough. The gliadin contributes elasticity, i.e the ability to "spring" back. The glutenin contributes extensibility, the ability to stretch without tearing. A well developed dough needs both elasticity (to hold its shape) and extensibility (to allow it to stretch and rise without tearing). As with any material, dough has its limits of elasticity and extensibility.
If you stretch an elastic band too much it will begin to lose its ability to spring back and even tear. This is the same thing for a dough that has risen too long - it has exceeded its limits of elasticity. Such a dough when baked in the oven will not have the required elasticity to hold its shape and will flop or come out flat. On the other side of the spectrum, a dough that has not risen enough, will have an excess of elasticity and the resulting bread texture will be thick and heavy and not light and fluffy.
A dough that is ready to bake is a dough that has reached the perfect balance of elasticity and extensibility. Such a dough still has enough elasticity in reserve so that when placed in the oven will be able to rise more and still have enough elasticity to retain its shape.
Instead of using complicated scientific instruments to measure the elasticity and extensibility balance, the "prod test" is a rough and ready method that provides amazingly similar results with sufficient accuracy.
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