The Fermenting Properties of Yeast Cells

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Abstract

This paper sought to identify the fermenting properties of yeast cells. Yeast can be identified as a tiny plant-like microorganism (Cox 122). The main purpose of yeast is to serve as a catalyst in the process of fermentation, which is essential in the making of bread (Nieman 570, par. 5). Yeast creates carbon dioxide gas, alcohol, and other organic compounds during growth (Vladimir 424). In this research, we utilized active dry yeast which was placed in two soda bottles containing all-purpose flour, granulated sugar and water at room temperature. The bottles were incubated at different temperatures, one in warm water and another in ice-cold water. The activity of the yeast was monitored using latex balloons that were secured on top of each bottle. The balloon placed on top of the bottle placed in warm water aired up indicating the occurrence of the fermentation process. The results were recorded in terms of the final circumference of the balloon and the thickness of the foam that was produced during the reaction. The balloon on top of the bottle placed in the warm water vessel had a final circumference of 35.56 cm, while the one in the ice water vessel remained zero. The final thickness of the foam in the bottle that was placed in a hot water bottle was 3.81 cm while that of the bottle in the ice water vessel. It can be identified that the warm water provided the optimum conditions for the yeast cells to grow, ferment and liberate ethanol and carbon dioxide. This is the typical fermentation process that is observed in the process of baking or alcohol production (Olsson and Nielsen 40).

Introduction and background

Yeast is a tiny plant-like microorganism that exists all around us- in soil, on plants and even in the air (Cox 122, par. 3). It has existed for so long, it is often referred to as the oldest plant cultivated by man (Nieman 567). Yeast mainly serves as a catalyst in the process of fermentation and thus is vital in bread making (Vladimir 424). Man used yeast before he knew how to write. Hieroglyphics suggest that the ancient Egyptian civilization were using living yeast and the process of fermentation to cause their bread to rise over 5,000 years ago (Maifeito 25, par. 5). Yeast creates carbon dioxide gas, alcohol, and other organic compounds during growth. The carbon dioxide produced is the agent that makes the bread rise (Vladimir 423, par. 2). The flavor is often created by other by-products. There are two types of dry yeast: Regular Active Dry Instant Yeast (also known as Fast Rising, Rapid Rise, Quick Rise, and/or Bread Machine Yeast) (Cox 125, par. 3). The Rapid rise is preferred over the active dry due to the fact that it rises twice faster than the active dry. Nutritional yeast, which isnt a live form of the fungi, can be used as a dietary supplement. It is high in protein and B vitamins and has a strong nutty or cheese flavor (Maifeito 25, par. 2). Products for vegans and for people with lactose intolerance often use nutritional yeast as a substitute for Parmesan cheese, and even some movie theatres have begun offering it as a healthy alternative topping for popcorn (Legras 2097, par. 2). There are three types of yeast. There is bakers yeast which is the type of yeast used in bread baking. The bakers yeast occurs in different forms, including Compressed Yeast, Active Dry Yeast and Quick-Rise Yeast (Legras 2094, par. 4). There is brewers yeast which is dried, inactive yeast that has no fermenting power (Legras 2097, par. 3). It is sold for nutritional qualities as it is very high in at least 10 separate B- vitamin factors, including Thiamine, Riboflavin, Niacin, Pyridoxine, Pantothenic Acid, Biotin, Choline, Inositol, Folic Acid, and Paraminobenzoic Acid (Nieman 570). Then we also have the nutritional yeast which is powdered yeast without leavening power, marketed for its protein and vitamin content Nieman 570, par.3). This research paper seeks to investigate the conditions that are necessary for yeast cells to liberate carbon dioxide.

Materials and Methods

Materials

2 empty, clean 1-liter soda bottles
2latex balloons
2 rubber bands
Glass measuring cup, 1 cup capacity
Teaspoon
Tablespoon
All-purpose flour
Granulated Sugar
Water at room temperature
2 packages of active dry yeast (1/4 ounces each) (Legras 2097)

Procedure

Each soda bottle was filled with one ¼ ounce package of Active Dry yeast, 1 teaspoon sugar, 2 tablespoons of all-purpose flour and 1 cup of water at room temperature.
One of the bottles was placed in a vessel containing warm water while the other was placed in a vessel containing ice-cold water.
A balloon was secured on top of each bottle.
The containers were kept at a constant temperature, the setups observed and the results recorded.

Variables

Dependent variable: release of carbon dioxide by the yeast which depends on the temperature

Control variable: Temperature, the yeast cells used in this experiment were placed at different temperatures.

Results

	Air (Balloon [cm])	Foam (cm)
Hot Water	35.56	3.81
Cold Water	0	1

Analysis

We observed a reaction in the bottle that was placed in warm water. A few minutes after placing the bottle in the vessel with warm water we visualized a foam layer building up, as the pressure continued to build up, we observed the balloon rising. At the beginning of the experiment, the circumference of the balloon was 0 cm, at the end of the experiment 20 minutes later, the circumference of the balloon had reached 35.56cm. The bottle that was placed in a vessel with ice water had no reaction and the circumference of the balloon was still zero at the end of the experiment. The bottle that was placed in a vessel with warm water caused the balloon to air up because of the following process; the warm water provided the appropriate temperature for the yeast to grow and therefore it made use of the nutrients provided by the sugar and flour multiply. As the yeast multiplied carbon dioxide and ethanol were produced through the process of fermentation (Nieman 570). The release of carbon dioxide caused the balloon to air up. The yeast in the bottle placed in the ice water vessel did not grow in spite of the fact that it had sugar and flour. This is due to the fact that the low temperature was not optimum for yeast to grow.

The bakers yeast that was utilized in this experiment is referred to as saccharomyces cerevisiae and is also commonly used in alcohol fermentation (Legras 2091). This yeast is often inhibited by salts and sugars due to dehydration (Nieman 573). Warm water was included in order to prevent dehydration of the yeast cells and provide a medium through which the temperature could be uniformly distributed in the reaction bottle. Yeast does not grow at low temperatures of 0 to 10 degrees Celsius, though they do not die. Previous studies that have been done indicate that yeast will grow with increasing temperatures and will reach optimal growth at 37 degrees Celsius depending on the species (Vladimir 425). The yeast cells often die at high temperatures. Yeast cells form a unique type of fungi that grows fast, that is why the balloon on top of the bottle placed in warm water was able to air up after 20 minutes.

Conclusion

This research project intended to identify the role of temperatures in the process of fermentation and detect the carbon dioxide produced. Yeast serves as a catalyst in the process of fermentation, which is essential in the making of bread (Nieman 574). The research made use of soda bottles to grow yeast using sugar and flour at different temperatures and observe the evidence of growth using carbon dioxide and alcohol production. The results obtained indicated that indeed yeast cells ferment sugars to release carbon dioxide and ethanol. This is the same process that is used in the production of alcohol and bread.

References

Cox, Teoh. Yeast ecology of Kombucha fermentation. international Journal of Food Microbiology (2004): 95 (2): 11926. Print.

Legras, Jean Luc. Bread, beer and wine: Saccharomyces cerevisiae diversity reflects human history. Molecular Ecology (2007): 2091- 2102. Print.

Maifeito, Loureiro. Spoilage yeasts in the wine industry. international Journal of Food Microbiology (2003): 2350. Print.

Nieman, Mark. Ascopore formation in the yeast Saccharomyces cerevisiae. Microbiology and Molecular Biology (2005): 56584. Print.

Olsson, Ostergaard and James Nielsen. Metabolic engineering of saccharomyces cerevisiae . Microbiology and Molecular Biology Reviews (2000): 34-50.Print.

Vladimir, Jiranek. Generation of Novel Wine Yeast Strains by Adaptive Evolution. Am. J. Enol. Vitic (2006): 42330. Print.

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