yeast fermentation experiment

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Inflate a Balloon with Yeast Fermentation Experiment: Lab Explained

Inflate a Balloon with Yeast…

INTRODUCTION

Yeasts are eukaryotic, single-celled microorganisms that belong to the fungal kingdom. When yeasts consume sugar and convert it to energy, they emit carbon dioxide, this is referred to as fermentation. The yeast will be more active and develop faster if there is more sugar present. While sugar and other sweets provide “food” for yeast, too much sugar can harm it by draining moisture from it and preventing it from growing. Too much sugar also delays the development of gluten. Increase the amount of yeast in the recipe or find a comparable recipe with less sugar.

Sweet yeast doughs will rise more slowly. Fermentation is sped up by a small amount of sugar, up to 3%. Warm water makes yeast grow, cold water has the reverse effect, and hot water kills yeast. Temperatures ranging from 0 to 47 degrees Celsius are suitable for yeast growth. Yeasts flourish in acidic settings with pH levels between 4.0 and 4.5. They can grow in lower pH environments than other bacteria, but not in alkaline environments. Yeasts are common in nature and can be found on grapes and other fruits. All yeast need food, moisture, and a controlled temperature environment in order to ferment. Its byproducts from food consumption include carbon dioxide, alcohol, and other organic molecules.

comparing yeast growth at various sugar concentrations.

50ml of water
Two balloons

(funnel may be needed to safely transfer the ingredients into the water bottles)

A kettle was used to boil the water, then cold water was added to the boiling water to get lukewarm water.
50ml of lukewarm water was added to each bottle.
¼ teaspoon of table sugar was then added to the first water bottle, then ½ teaspoon of table sugar was added to the other water bottle.
½ teaspoon of rapid-rise yeast was then added to each solution and mixed.
After mixing, a balloon was placed on each water bottle/ tube and sealed securely.
The contents were mixed periodically.

(N.B- A string may be used to seal the balloon placed on water bottles).

OBSERVATIONS

During the experiment, 500ml water bottles were used. Then 50ml of lukewarm water was added to each bottle, after that, ½ teaspoon of sugar was added to the 1 st bottle then ¼ teaspoon of sugar was added to the 2 nd bottle. Finally, ½ teaspoon of rapid-rise yeast was added to both bottles, then the balloons were placed on each tube and securely sealed. The balloons were checked at the time interval of 15min to observe any changes, when glancing at the balloons, it was noticed that the balloons were getting bigger and bigger every time on top of the water bottles. Warmth and moisture are necessary for yeast to function, that is why lukewarm water was added. Sugar was converted to carbon dioxide by yeast.

Some bubbles were also observed in the yeast mixture during the experiment, it was the small carbon dioxide gas bubbles produced by the yeast as it “ate” the sugar.

As the yeast continued to react, additional sugar was transformed into carbon dioxide gas. The balloons were filled with this gas, which caused them to inflate. It was also observed that the balloon on the water bottle that had ½ teaspoon of sugar was growing bigger at a faster rate than the one that had ¼ teaspoon of sugar.

This can show that glucose concentration increases fermentation production in yeast. The more sugar present, the more active the yeast becomes, and the faster it grows. The balloon on the bottle that had less sugar was growing at a slow rate compared to the other one, even had fewer bubbles visible. It was seen that the concentration of sugar plays a vital role in the rate of fermentation, the more sugar present, the more active the yeast becomes, and the faster it grows. This also showed why the fermentation rates of the sugars differ over time. Both balloons grew until they reached a point where they grew no more.

During the experiment, when the balloons were growing bigger and bigger, using the time interval of 15 minutes, the circumferences of the balloons were measured. From the measurements, it can be safely concluded that the balloon on the water bottle with ½ teaspoon of sugar grew bigger and faster than the one on the water bottle with ¼ teaspoon of sugar. Another thing observed is that as time went by the fermentation rate of both the balloons started to decrease.

From what was observed during the practice of the experiment, it can be concluded that the more sugar there is, the more active the yeast will be and the faster its growth. THIS CAN BE APPLIED IN REAL LIFE: fermentation can be used to preserve food, preventing rotting or harmful microorganisms from growing in the food. Can also apply when baking bread.

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I would like to cite this article for a research paper, would it be possible to disclose the authors name(s), and date this was published?

Yeast Fermentation Experiment

Fermentation is a fascinating process that kids can easily explore through a simple experiment using yeast and sugar. This hands-on activity teaches students about fermentation and introduces them to the scientific method, data collection, and analysis.

Investigate how different types of sugar (white, brown, and honey) affect the rate of yeast fermentation by measuring the amount of carbon dioxide (CO₂) produced.

Example Hypothesis: If yeast is added to different types of sugar, then the type of sugar will affect the amount of carbon dioxide produced, with white sugar producing more CO₂ than the others.

💡 Learn more about using the scientific method [here] and choosing variables .

Watch the Video:

Active dry yeast
White sugar
Brown sugar
Measuring spoons and measuring cups
Small bottles or test tubes
Rubber bands
Ruler or measuring tape
Notebook and pen for recording data ( grab free journal sheets here )
Printable Experiment Page (see below)

Instructions:

STEP 1. Prepare a yeast solution by dissolving a packet of active dry yeast in warm water according to the package instructions.

STEP 2. Label 3 bottles and add 1 tablespoon of white sugar to the “White Sugar” bottle. Add 1 tablespoon of brown sugar to the “Brown Sugar” bottle. Measure 1 tablespoon of honey and add it to the “Honey” bottle.

STEP 3. Measure and pour an equal amount of the yeast solution into each bottle, ensuring the yeast is well mixed with the sugar.

STEP 4. Quickly stretch a balloon over the mouth of each bottle. Secure the balloons with rubber bands if needed. Ensure the balloons are sealed tightly to prevent CO₂ from escaping.

STEP 5. Place the bottles in a warm, consistent environment to promote fermentation.

STEP 6. Observe and record the size of the balloons at regular intervals (e.g., every 15 minutes) for 1-2 hours. Use a ruler or measuring tape to measure the circumference of each balloon.

TIP: Note the time it takes for the balloons to start inflating and the differences in balloon size over time for each type of sugar.

STEP 7: Analyze the data by comparing the amount of CO₂ produced (balloon size) for each type of sugar. Create a graph showing the balloon size over time for each sugar type.

STEP 8. Determine which sugar type resulted in the most and least CO₂ production. Discuss possible reasons for the differences, considering what each sugar is made of. Think about whether the results support or disprove the hypothesis. Can you come up with further experiments or variations to explore other factors affecting yeast fermentation?

Free Printable Yeast and Sugar Experiment Project

Grab the free fermentation experiment worksheet here. Join our STEM club for a printable version of the video!

The Science Behind Yeast Fermentation

For Our Younger Scientists: Yeast is a type of fungus that feeds on sugars. When you mix yeast with sugar and water, it starts to eat the sugar and convert it into alcohol and carbon dioxide gas. The gas gets trapped in the balloon, causing it to inflate. This shows that fermentation is happening!

Yeast fermentation is a biological process where yeast converts sugars into alcohol and carbon dioxide (CO₂) in the absence of oxygen. This process is used in baking, brewing, wine making and biofuel production. How much fermentation occurs can vary depending on the type of sugar used.

Yeast contains enzymes that break down sugar molecules through a series of chemical reactions . Here’s how it works:

Enzymes are molecules, usually proteins, that act as catalysts to speed up chemical reactions within living organisms.

First the yeast is mixed with warm water, and it becomes activated. The warm environment “wakes up” the yeast cells, preparing them to consume sugars.

Yeast cells produce enzymes that break down sugar molecules (sucrose, glucose, and fructose) into simpler molecules. This process is called glycolysis. During glycolysis, sugar molecules are converted into pyruvate, releasing a small amount of energy.

In the absence of oxygen (anaerobic conditions), yeast cells convert pyruvate into ethanol (alcohol) and carbon dioxide gas (CO₂). The carbon dioxide produced during fermentation is what inflates the balloons in the experiment.

Different Sugars & Fermentation

Different sugars can affect the rate of fermentation. This is how:

White Sugar (Sucrose): Composed of glucose and fructose and is easily broken down by yeast, leading to efficient CO₂ production.
Brown Sugar: Contains sucrose along with molasses, which includes minerals and additional nutrients. May result in a slightly different fermentation rate due to its composition.
Honey: Contains a mixture of glucose, fructose, and other components. The additional components can influence the fermentation process, potentially leading to different CO₂ production rates compared to pure sucrose.

The amount of CO₂ produced depends on how easily the yeast can break down the sugar molecules and convert them into ethanol and CO₂. Sugars that are more readily broken down by yeast will typically produce more CO₂ faster.

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