Thursday, January 22, 2009

Effects Of Different Sweeteners On The Fermentation Of Yeast

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Over 5000 years ago, the Egyptians and Babylonians were able to utilize the fermentation of wild yeast in the form of sourdough to make raised bread (“Yeast,” 2002). Yeast is a microorganism found in soil, plants, and air; therefore, these ancient peoples did not know what caused their bread dough to rise (Fleischmann‘s, 1996). Anton Leewenhoek first observed yeast cells under his newly discovered microscope in 1676 (Fleischmann‘s, 1996). In 1859, Louis Pasteur found that yeast was actually a single-celled microorganism that feeds on carbohydrates (sugar and flour) and produces carbon dioxide gas (CO2 ­ ) (Fleischmann‘s).

There are over 600 species of yeasts, but only a few are used to make breads and alcoholic beverages. Other yeasts can produce illness and can spoil breads. Yeasts reproduce rapidly through fission or budding and grow especially well in substances containing sugar (“Yeasts“). The yeasts are classified in the kingdom Fungi, phyla Ascomycota and Basidiomycota (“Yeast“). Yeasts of the genus Saccharomyces have been long used commercially in the fermentation process of making alcohol and breads (“Yeasts“). Fermentation is a process by which a living cell, such as yeast, obtains energy through the breakdown of glucose and other simple sugars (“Fermentation,” 2002).

In breadmaking the yeasts feed upon the carbohydrates (sugar and flour) in the dough, forming carbon dioxide gas and ethyl alcohol, which are later “driven off” in the baking process (“Yeasts,” 2002). Yeast activity initially increases during baking, then the yeast dies as the temperature reaches 140° F (Fleischmann‘s, 1996). The heat causes starch in the dough to gelatinize and then form protein chains with rigid bonds (Fleischmann’s, 1996).

In this experiment, the fermentation of yeast using table sugar (sucrose) and honey (fructose and glucose) was compared to the fermentation of yeast using Equal® Spoonful (aspartame). Both table sugar and honey contain simple sugars which yeast utilize to produce energy in the fermentation process. The artificial sweetener Equal® Spoonful contains phenylalanine (an amino-acid) and the asparatame (sweetening agent), non-nutritive agents (Equal®)..


Will Equal® Spoonful (Aspartame) ferment dry active yeast as well as table sugar (sucrose) and honey (glucose and fructose)?

As my mother is a diabetic, I wanted to find out if Equal® Spoonful could be used to bake bread in place of ordinary table sugar or honey. For dry active yeast to ferment properly it must have nutrients, specifically carbohydrates (sugars). The yeast was fed the three different sweeteners mentioned above and the fermentation process observed. As Equal® Spoonful is a nonnutritive type sweetener, I did not think it would ferment the yeast properly.


If sugar is needed to ferment yeast, then table sugar (sucrose) and honey (fructose and glucose) will produce more carbon dioxide gas “foam” by fermenting yeast better than Equal® Spoonful (Aspartame), an artificial “sugar-free” substitute.


WARM WATER (120° - 130° F)
1 TEASPOON OF Equal® Spoonful

[Note: The reason Equal® Spoonful was chosen over regular packets of Equal® : One teaspoon of the Equal® Spoonful is equivalent to one teaspoon of table sugar; whereas, one packet Equal® is equivalent to two teaspoons of table sugar.]

Once the materials were gathered the cups were mark as indicated in the procedure below. The four cups were placed on a table where they could be seen and the contents measured easily. Measurements were taken as indicated in the above procedure and recorded on a piece of paper.


Place a piece of masking tape on each of the 4 cups vertically.

Mark cups # 1 - 4.

Mark on tape indicating ¼ inch measurements with zero a bottom of cup.

Place thermometer in pitcher and fill with tap water until it reads between 120° - 130° F (warm water).

Fill each of the four cups with warm water to the 1 ¼” mark on tape.

Add 1 teaspoon (use measuring teaspoon) of dry yeast (taken for the same jar of yeast) to each cup of warm water.

Add nothing more to cup # 1.

Add 1 teaspoon (use measuring teaspoon) of table sugar to cup # 2.

Add 1 teaspoon (use measuring teaspoon) of Equal® Spoonful to cup # 3.

Add 1 teaspoon (use measuring teaspoon) of Honey to cup # 4.

Stir ingredients in each cup with a clean teaspoon 10 rotations each.

Record amount in each cup; this is the 0 minute measurement.

Record amount in each cup (including “foam”) in each cup every five minutes thereafter for 30 minutes.

Record final amount in each cup at 45 minute mark.


Independent (Manipulative) variable: Type of sweetener -- table sugar (sucrose), honey (fructose and glucose), and Equal® Spoonful (Aspartame) .

Dependent (Responding) variable: “Foam” produced as a result of carbon dioxide gas formation during fermentation process by yeast.

Controlled variables: Volume of water, temperature of water, volume of yeast, type of yeast, capacity of cup, time intervals, and number of stirs when mixing ingredients.

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