yeast and sugar experiment

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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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Helpful Science Resources To Get You Started

Here are a few resources that will help you introduce science more effectively to your kiddos or students and feel confident presenting materials. You’ll find helpful free printables throughout.

• Best Science Practices (as it relates to the scientific method)
• Science Vocabulary
• All About Scientists
• Free Science Worksheets
• DIY Science Kits
• Science Tools for Kids
• Scientific Method for Kids
• Citizen Science Guide
• Join us in the Club

Printable Science Projects For Kids

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• 90+ classic science activities  with journal pages, supply lists, set up and process, and science information.  NEW! Activity-specific observation pages!
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• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
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The fermentation of sugars using yeast: A discovery experiment

Charles Pepin (student) and Charles Marzzacco (retired), Melbourne, FL

Introduction

Enzyme catalysis 1  is an important topic which is often neglected in introductory chemistry courses. In this paper, we present a simple experiment involving the yeast-catalyzed fermentation of sugars. The experiment is easy to carry out, does not require expensive equipment and is suitable for introductory chemistry courses.

The sugars used in this study are sucrose and lactose (disaccharides), and glucose, fructose and galactose (monosaccharides). Lactose, glucose and fructose were obtained from a health food store and the galactose from Carolina Science Supply Company. The sucrose was obtained at the grocery store as white sugar. The question that we wanted to answer was “Do all sugars undergo yeast fermentation at the same rate?”

Sugar fermentation results in the production of ethanol and carbon dioxide. In the case of sucrose, the fermentation reaction is:

\[C_{12}H_{22}O_{11}(aq)+H_2 O\overset{Yeast\:Enzymes}{\longrightarrow}4C_{2}H_{5}OH(aq) + 4CO_{2}(g)\]

Lactose is also C 12 H 22 O 11  but the atoms are arranged differently. Before the disaccharides sucrose and lactose can undergo fermentation, they have to be broken down into monosaccharides by the hydrolysis reaction shown below:

\[C_{12}H_{22}O_{11} + H_{2}O \longrightarrow 2C_{6}H_{12}O_{6}\]

The hydrolysis of sucrose results in the formation of glucose and fructose, while lactose produces glucose and galactose.

sucrose + water \(\longrightarrow\) glucose + fructose

lactose + water \(\longrightarrow\) glucose + galactose

The enzymes sucrase and lactase are capable of catalyzing the hydrolysis of sucrose and lactose, respectively.

The monosaccharides glucose, fructose and galactose all have the molecular formula C 6 H 12 O 6  and ferment as follows:

\[C_{6}H_{12}O_{6}(aq)\overset{Yeast Enzymes}{\longrightarrow}2C_{2}H_{5}OH(aq) + 2CO_{2}(g)\]

In our experiments 20.0 g of the sugar was dissolved in 100 mL of tap water. Next 7.0 g of Red Star ®  Quick-Rise Yeast was added to the solution and the mixture was microwaved for 15 seconds at full power in order to fully activate the yeast. (The microwave power is 1.65 kW.) This resulted in a temperature of about 110  o F (43  o C) which is in the recommended temperature range for activation. The cap was loosened to allow the carbon dioxide to escape. The mass of the reaction mixture was measured as a function of time. The reaction mixture was kept at ambient temperature, and no attempt at temperature control was used. Each package of Red Star Quick-Rise Yeast has a mass of 7.0 g so this amount was selected for convenience. Other brands of baker’s yeast could have been used.

This method of studying chemical reactions has been reported by Lugemwa and Duffy et al. 2,3  We used a balance good to 0.1 g to do the measurements. Although fermentation is an anaerobic process, it is not necessary to exclude oxygen to do these experiments. Lactose and galactose dissolve slowly. Mild heat using a microwave greatly speeds up the process. When using these sugars, allow the sugar solutions to cool to room temperature before adding the yeast and microwaving for an additional 15 seconds.

Fermentation rate of sucrose, lactose alone, and lactose with lactase

Fig. 1 shows plots of mass loss vs time for sucrose, lactose alone and lactose with a dietary supplement lactase tablet added 1.5 hours before starting the experiment. All samples had 20.0 g of the respective sugar and 7.0 g of Red Star Quick-Rise Yeast. Initially the mass loss was recorded every 30 minutes. We continued taking readings until the mass leveled off which was about 600 minutes. If one wanted to speed up the reaction, a larger amount of yeast could be used. The results show that while sucrose readily undergoes mass loss and thus fermentation, lactose does not. Clearly the enzymes in the yeast are unable to cause the lactose to ferment. However, when lactase is present significant fermentation occurs. Lactase causes lactose to split into glucose and galactose. A comparison of the sucrose fermentation curve with the lactose containing lactase curve shows that initially they both ferment at the same rate.

Fig. 1. Comparison of the mass of CO 2 released vs time for the fermentation of sucrose, lactose alone, and lactose with a lactase tablet. Each 20.0 g sample was dissolved in 100 mL of tap water and then 7.0 g of Red Star Quick-Rise Yeast was added.

However, when the reactions go to completion, the lactose, lactase and yeast mixture gives off only about half as much CO 2  as the sucrose and yeast mixture. This suggests that one of the two sugars that result when lactose undergoes hydrolysis does not undergo yeast fermentation. In order to verify this, we compared the rates of fermentation of glucose and galactose using yeast and found that in the presence of yeast glucose readily undergoes fermentation while no fermentation occurs in galactose.

Fig. 2. Comparison of the mass of CO 2 released vs time for the fermentation of sucrose, glucose and fructose. Each 20 g sugar sample was dissolved in 100 mL of water and then 7.0 g of yeast was added.

Fermentation rate of sucrose, glucose and fructose

Next we decided to compare the rate of fermentation of sucrose with that glucose and fructose, the two compounds that make up sucrose. We hypothesized that the disaccharide would ferment more slowly because it would first have to undergo hydrolysis. In fact, though, Fig. 2 shows that the three sugars give off CO 2  at about the same rate. Our hypothesis was wrong. Although there is some divergence of the three curves at longer times, the sucrose curve is always as high as or higher than the glucose and fructose curves. The observation that the total amount of CO 2  released at the end is not the same for the three sugars may be due to the purity of the fructose and glucose samples not being as high as that of the sucrose.

Fermentation rate and sugar concentration

Next, we decided to investigate how the rate of fermentation depends on the concentration of the sugar. Fig. 3 shows the yeast fermentation curves for 10.0 g and 20.0 g of glucose. It can be seen that the initial rate of CO 2  mass loss is the same for the 10.0 and 20.0 g samples. Of course the total amount of CO 2  given off by the 20.0 g sample is twice as much as that for the 10.0 g sample as is expected. Later, we repeated this experiment using sucrose in place of glucose and obtained the same result.

Fig. 3. Comparison of the mass of CO 2  released vs time for the fermentation of 20.0 g of glucose and 10.0 g of glucose. Each sugar sample was dissolved in 100 mL of water and then 7.0 g of yeast was added.

Fermentation rate and yeast concentration

After seeing that the rate of yeast fermentation does not depend on the concentration of sugar under the conditions of our experiments, we decided to see if it depends on the concentration of the yeast. We took two 20.0 g samples of glucose and added 7.0 g of yeast to one and 3.5 g to the other. The results are shown in Fig. 4. It can clearly be seen that the rate of CO 2  release does depend on the concentration of the yeast. The slope of the sample with 7.0 g of yeast is about twice as large as that with 3.5 g of yeast. We repeated the experiment with sucrose and fructose in place of glucose and obtained similar results.

Fig. 4. Comparison of the mass of CO 2 released vs time for the fermentation of two 20.0 g samples of glucose dissolved in 100 mL of water. One had 7.0 g of yeast and the other had 3.5 g of yeast.

In hindsight, the observation that the rate of fermentation is dependent on the concentration of yeast but independent of the concentration of sugar is not surprising. Enzyme saturation can be explained to students in very simple terms. A molecule such as glucose is rather small compared to a typical enzyme. Enzymes are proteins with large molar masses that are typically greater than 100,000 g/mol. 1  Clearly, there are many more glucose molecules in the reaction mixture than enzyme molecules. The large molecular ratio of sugar to enzyme clearly means that every enzyme site is occupied by a sugar molecule. Thus, doubling or halving the sugar concentration cannot make a significant difference in the initial rate of the reaction. On the other hand, doubling the concentration of the enzyme should double the rate of reaction since you are doubling the number of enzyme sites.

The experiments described here are easy to perform and require only a balance good to 0.1 g and a timer. The results of these experiments can be discussed at various levels of sophistication and are consistent with enzyme kinetics as described by the Michaelis-Menten model. 1  The experiments can be extended to look at the effect of temperature on the rate of reaction. For enzyme reactions such as this, the reaction does not take place if the temperature is too high because the enzymes get denatured. The effect of pH and salt concentration can also be investigated.

• Jeremy M. Berg, John L. Tymoczko and Lubert Stryer,  Biochemistry , 6th edition, W.H. Freeman and Company, 2007, pages 205-237.
• Fugentius Lugemwa, Decomposition of Hydrogen Peroxide,  Chemical Educator , April 2013, pages 85-87.
• Daniel Q. Duffy, Stephanie A. Shaw, William D. Bare, Kenneth A. Goldsby, More Chemistry in a Soda Bottle, A Conservation of Mass Activity,  Journal of Chemical Education , August 1995, pages 734-736.
• Jessica L Epstein, Matthew Vieira, Binod Aryal, Nicolas Vera and Melissa Solis, Developing Biofuel in the Teaching Laboratory: Ethanol from Various Sources,  Journal of Chemical Education , April 2010, pages 708–710.

More about April 2015

Department of Chemistry 200 University Ave. W Waterloo, Ontario, Canada N2L 3G1

[email protected]

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Fermentation of glucose using yeast

• Four out of five

Carry out this practical and use the follow-up questions to explore an important fermentation reaction

Add some fresh context to this classic experiment with  Is fermented food and drink good for us?  in  Education in Chemistry . The article tucks into the science of fermentation and its everyday applications, from kombucha to kefir, and puts the supposed health benefits under the microscope. 

Beer and wine are produced by fermenting glucose with yeast. Yeast contains enzymes that catalyse the breakdown of glucose to ethanol and carbon dioxide. In this experiment, learners will set up a glucose solution to ferment and then test the products. You may also demonstrate distilling the fermentation mixture to separate the ethanol formed or set this as a learner activity. 

Download this

Carry out the fermentation of glucose using yeast with 14–16 learners. Observe and test the products, follow up with questions to consolidate learning and/or the distillation of ethanol.

The experiment is part of the  Nuffield practical collection , developed by the Nuffield Foundation and the Royal Society of Chemistry. Delve into a wide range of chemical concepts and processes with this collection of over 200 step-by-step practicals.

Learning objectives

• Carry out and observe a fermentation reaction.
• Test the products of a fermentation reaction.
• Explain the conditions needed for a fermentation reaction.

The experiment allows learners to cover the first two learning objectives. Use the questions to test their results and observations. Questions 4–6 cover the third learning objective and ask learners to explain the conditions required. Use question 7 to see if learners can connect this experiment to rates of reaction. To stretch learners, expand this question and ask them to write a full plan. Find the answers in the Teacher notes . 

How to use this resource

Set learners the first part of the experiment. It usually yields results within a lesson if the water is at the correct temperature and the reaction mixture is well mixed to begin with. It also depends on the freshness of the yeast. Dried yeast does work. If fermentation is not rapid because of the yeast used, then carry the whole experiment over to the next lesson.

For an alternative practical arrangement to part 1, use a bung and delivery tube to bubble the carbon dioxide through limewater. Or watch the Identifying ions practical video from 08:20 to see how to use a pipette to collect the gas when testing for carbonate ions. 

In the second part of the experiment, you can demonstrate distilling the reaction mixture. Watch the Fractional distillation  and Simple distillation videos and download the accompanying resources for setup, method and more learner-facing activities on simple distillation.

If you demonstrate distillation, pool the class results and filter the groups’ solutions into your distillation flask. Significant quantities of yeast will produce foaming and you can carry this over into the product if you do not filter the reaction mixture. Collect the fraction between 77–82°C. Ethanol boils at 78°C. This fraction should burn easily compared with the non-flammable original solution. Pour the ethanol away immediately and do not keep or reuse it.

Alternatively, set the distillation practical as a learner activity. Individuals or pairs may not produce enough ethanol to complete the distillation so learners may need to combine their solutions and work in groups.

More resources

• Use our  organic chemistry worksheet on alcohols  with 14–16 learners for practice in applying knowledge in context, including burning alcohols in cooking and as fuels.
• Link your lessons on fermentation and bioethanol to UN sustainable development goal 8 while developing learners’ literacy skills with this resource on  E10 petrol and climate change .
• Learn how a circular approach to manufacturing at British Sugar means there is virtually zero waste, including how they create coproducts such as bioethanol, by watching Paul’s  video job profile .
• Download the classroom activity and display the  fractional distillation  poster in your classroom to help 14–16 learners understand this important separating technique.

Technician notes

Read our  Standard health and safety guidance  and carry out a risk assessment before running any live practical.

Ensure learners wear safety glasses.

Be aware that if the fermentation is fast, the mixture may overflow from the flask.

Equipment (per group)

• 100 cm 3  conical flask
• 50 cm 3  measuring cylinder
• Boiling tube
• Boiling tube rack
• Access to a mass balance, correct to 1 decimal place
• Cotton wool – enough to plug the conical flask
• Safety glasses

Chemicals (per group)

• Glucose, 5 g – not currently classed as hazardous. See CLEAPSS Hazcard HC040c for more information.
• Yeast (as fast acting as possible), 1 g

Wear eye protection and measure 5 g of calcium hydroxide.

Add, while stirring, to 300 cm 3 of water in a large beaker.

Continue to stir the suspension, then pour it into a clean, labelled 2.5 dm 3 screw-top bottle using a funnel.

Fill the bottle with distilled water and tightly close the lid. Invert it to mix.

Leave the bottle overnight to allow the suspension to settle.

When required, slowly pour the limewater into small, labelled bottles.

Add more distilled water and/or calcium hydroxide to the stock bottle as required.

• 50 cm 3  of warm water 30–40°C
• Put 5 g of glucose in the conical flask and add 50 cm 3 of warm water. Swirl the flask to dissolve the glucose.
• Add 1 g of yeast to the solution and loosely plug the top of the flask with cotton wool.
• Wait while fermentation takes place. The time it takes will depend on the temperature, how well you mixed the reactants and the yeast’s freshness.
• Add 5 cm 3 of limewater to the boiling tube. Avoid contact with your skin as limewater is an irritant.
• Remove the cotton wool and pour the invisible gas into the boiling tube containing limewater. Take care not to pour in any liquid as well.
• Gently swirl the limewater in the boiling tube and note what happens.
• Replace the cotton wool in the top of the flask.

Source: © Royal Society of Chemistry

Set up the equipment as shown or use a pipette or bung and delivery tube instead of cotton wool to bubble the carbon dioxide through limewater

• Remove the cotton wool and note the smell of the solution.

If you are going to observe the distillation then you, or your teacher, will:

• Filter all the groups’ solutions into a distillation flask.
• Distil the mixture and collect the distillation fraction between 77–82°C.

The distillation fraction should easily burn.

Fermentation of glucose using yeast student sheet

Fermentation of glucose using yeast teacher notes, additional information.

This is a resource from the  Practical Chemistry project , developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany  Practical Physics  and  Practical Biology . Updated in 2024 with additional student questions by Neil Goalby.

© Nuffield Foundation and the Royal Society of Chemistry

More Neil Goalby

Carbon allotropes | Johnstone’s triangle worksheets | 14–16 years

Covalent bonding | Johnstone’s triangle worksheets | 14–16 years

Metallic bonding | Johnstone’s triangle worksheets | 14–16 years

• 14-16 years
• 16-18 years
• Practical experiments
• Teacher notes
• Biological chemistry
• Reactions and synthesis

Specification

• Ethanol is produced industrially by fermentation of glucose. The conditions for this process.
• Ethanol produced industrially by fermentation is separated by fractional distillation and can then be used as a biofuel.
• AT.3 Use of appropriate apparatus and techniques for conducting and monitoring chemical reactions, including appropriate reagents and/or techniques for the measurement of pH in different situations.
• Aqueous solutions of ethanol are produced when sugar solutions are fermented using yeast. Students should know the conditions used for fermentation of sugar using yeast.
• AT4 Safe use of a range of equipment to purify and/or separate chemical mixtures including evaporation, filtration, crystallisation, chromatography and distillation.
• 9.33C Describe the production of ethanol by fermentation of carbohydrates in aqueous solution, using yeast to provide enzymes
• 9.34C Explain how to obtain a concentrated solution of ethanol by fractional distillation of the fermentation mixture
• 3 Use of appropriate apparatus and techniques for conducting and monitoring chemical reactions, including appropriate reagents and/or techniques for the measurement of pH in different situations
• Use of appropriate apparatus and techniques for conducting and monitoring chemical reactions, including appropriate reagents and/or techniques for the measurement of pH in different situations
• (s) how ethanol (an alcohol) is made from sugars by fermentation using yeast

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Science project, growing yeast: sugar fermentation.

Yeast is most commonly used in the kitchen to make dough rise. Have you ever watched pizza crust or a loaf of bread swell in the oven? Yeast makes the dough expand. But what is yeast exactly and how does it work? Yeast strains are actually made up of living eukaryotic microbes, meaning that they contain cells with nuclei. Being classified as fungi (the same kingdom as mushrooms), yeast is more closely related to you than plants! In this experiment we will be watching yeast come to life as it breaks down sugar, also known as sucrose , through a process called fermentation . Let’s explore how this happens and why!

What is sugar’s effect on yeast?

• 3 Clear glass cups
• 2 Teaspoons sugar
• Water (warm and cold)
• 3 Small dishes
• Permanent marker

• Fill all three dishes with about 2 inches of cold water
• Place your clear glasses in each dish and label them 1, 2, and 3.
• In glass 1, mix one teaspoon of yeast, ¼ cup of warm water, and 2 teaspoons of sugar.
• In glass 2, mix one teaspoon of yeast with ¼ cup of warm water.
• In glass 3, place one teaspoon of yeast in the glass.
• Observe each cups reaction. Why do you think the reactions in each glass differed from one another? Try using more of your senses to evaluate your three glasses; sight, touch, hearing and smell especially!

The warm water and sugar in glass 1 caused foaming due to fermentation. 

Fermentation is a chemical process of breaking down a particular substance by bacteria, microorganisms, or in this case, yeast. The yeast in glass 1 was activated by adding warm water and sugar. The foaming results from the yeast eating the sucrose. Did glass 1 smell different? Typically, the sugar fermentation process gives off heat and/or gas as a waste product. In this experiment glass 1 gave off carbon dioxide as its waste.

Yeast microbes react different in varying environments. Had you tried to mix yeast with sugar and cold water, you would not have had the same results. The environment matters, and if the water were too hot, it would kill the yeast microorganisms. The yeast alone does not react until sugar and warm water are added and mixed to create the fermentation process. To further investigate how carbon dioxide works in this process, you can mix yeast, warm water and sugar in a bottle while attaching a balloon to the open mouth. The balloon will expand as the gas from the yeast fermentation rises.

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