What must be in the oven yet can not be baked? grows in the heat yet shuns the light of day? looks like skin but is fine as hair? Here’s a clue -it makes your bread soft and fluffy!
Well, the sun rises in the east, and the bread rises because of yeast!
Yes, the answer to all these questions is Yeast.
What is Yeast?
Yeast is a tiny, single-celled organism belonging to the Fungi kingdom. Like every other microorganism, yeast multiplies under favourable conditions.
Did you know?
While there are about 160 known species of yeast, Saccharomyces cerevisiae, commonly known as baker’s yeast, is the one most often used in the kitchen. Yeast is tiny: Just one gram holds about 25 billion cells!
But Yeast all by itself doesn’t do much. To do everything that we mentioned earlier, it needs some help. And those are its three most helpful companions- warm temperature, water, and glucose. These three conditions activate the yeast, sort of bring them to life. Once active, yeast indulges in the process of fermentation, after which we get some of the yummiest food known to mankind. But before we get into details, let’s understand a bit about fermentation.
What is Fermentation?
Fermentation is a process that helps break down nutrients (like glucose) in food, making them easier to digest than their unfermented counterparts. The breakdown process is done by microorganisms like fungi for example yeast, mold or bacteria. It occurs in the cells of these microorganisms and also the muscles of animals including humans. It is an anaerobic (i.e. without the direct supply of oxygen) pathway in which glucose is broken down. These microorganisms break down molecules of glucose through a process called glycolysis. You must be thinking that all these complex chemical reactions might happen just in chemistry labs, but you couldn’t be more wrong! There are literally thousands of food items that involve fermentation as a part of their preparation. For example, bread, naan, dhokla, wine, cheese, yogurt, etc.
Did You Know?
In 1857, Louis Pasteur discovered that yeast is a living organism whose activity causes fermentation.
Now that we have read and understood what these small granules of yeast are capable of doing, let’s try it out and see it in action, right away. Let’s make some gas and blow a balloon!
Things you’ll need:
As the yeast feeds on the sugar, it produces carbon dioxide, ethanol, and energy. With no place to go but up, the carbon dioxide slowly fills the balloon. Whereas in the second bottle, the balloon doesn’t inflate because there’s no sugar. Without sugar, the yeast doesn’t have any food to feed on and so there’s no fermentation and hence no gas.
While making bread, a very similar process happens. The bread rises due to the carbon dioxide from yeast. It fills thousands of balloon-like bubbles in the dough. Once the bread has baked, this is what gives a loaf of bread its airy texture. Another factor that influences the rising of the bread is the alcohol produced in fermentation. While at room temperature, the alcohol is liquid, but while baking bread, when the bread hits the oven, the alcohol begins to evaporate, transforming into gas bubbles that contribute to the rise of the bread.
What else can you do?
Try the same experiment, but this time use about a tablespoon of baking powder instead of yeast, but without the sugar. Did you notice any difference? Which ingredient takes longer to fill up the balloon?
You could also try the same experiment using hotter and colder water. Use a thermometer to measure the temperature of the water. At what temperature is the yeast most active? At what temperatures is it unable to fill up the balloon? Share your observations with us in the comment section!
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