Yeast: Let’s have a closer look

Yeast finds a lot of applications in the food industry and is an important ingredient of bread, pizzas and alcoholic beverages like wine, beer etc. They cause the bread to rise and juices to ferment. Currently research is also happening on the how to transform plants into bio fuels under the action of yeast.

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Yeasts are single celled micro organisms belonging to class of fungi. The cells are smaller than animal and plant cells but slightly larger than bacteria. The yeast cells when viewed under a microscope are oval shaped. They do have a thin cell wall and clear cytoplasm. The nucleus cannot be seen unless special staining techniques are used.  There are no chloroplasts in yeast cells.


Yeast is rich in vitamin B. A form of yeast called brewer’s yeast is used as a diet supplement. Yeasts can harm as well as heal. It could cause skin infections on one hand while on the other hand it could produce large quantities of certain hormones and enzymes for medical purposes like healing wounds and reducing inflammation.

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Yeast cell can produce both sexually and asexually by budding under right conditions of moisture, temperature and food supply. Some of their enzymes chemically break down the sugars into products that the cell can use and others can make simple sugars which are found in other organisms. The breaking down of sugars, or fermentation, produces alcohol and carbon dioxide as by-products.

While preparing the dough used in bread/pizza making, yeast is also added to the dough as a raising or leavening agent. Addition of yeast causes the dough to rise. The most common yeast used in bread making is Saccharomyces cerevisiae. It feeds on the sugars present in the bread dough, producing carbon dioxide. This forms bubbles within the dough, causing it to expand. Other ingredients in the mixture have an effect on the speed of the fermentation – sugar and eggs speed it up while fats and salt slow it down.

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