Hop To It! The Science Behind Beer

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Kate Williams
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5.73

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Brewing beer involves a series of complex biochemical reactions.

Barley, water, hops, and yeast. How do four simple ingredients come together to make thousands of different kinds of beer? The answer lies in the science of brewing. Brewing beer involves a series of complex biochemical reactions. For example, starches break down to form sugars. Sugars break down to form alcohol

Let’s learn about the biochemical reactions behind beer in more detail. 

Did you know?

Ultraviolet (UV) light causes a chemical reaction in hops. This reaction gives beer a skunk-like odour. Most beer is bottled in dark brown glass to prevent this from happening.

What is malting?

The first step in brewing is malting. This involves soaking the grain in water. Usually, this grain is barley, a source of starch. Soaking barley allows its starches to germinate (or sprout). This way, they become softer and easier to extract for the next step. 

Photograph showing sprouted barley seeds
 Photograph showing sprouted barley seeds (Source: Finlay McWalte’s friend SJB [CC BY-SA 3.0] via Wikimedia Commons).

Once the barley has germinated, it is dried out. This is an important step. The temperature used to dry the barley will determine the type of malt it will form. Barley dried at higher temperatures produces a dark malt. Barley dried at lower temperatures produces a light malt. Malt affects both the colour and the flavour of the beer.

What is mashing?

The next step is a process called mashing. Brewers add hot water to the malted barley. This activates temperature-dependent enzymes. Enzymes are proteins that exist in all organisms. They bind to other molecules and increase the speed of chemical reactions. Enzymes convert starches to sugars through a process called saccharification

Once the mashing process is complete, the malted barley can be filtered out of the mixture. The result is a sugary liquid called wort.

Breakdown of starch to glucose
Diagram showing the chemical reaction of starch and water to form maltose (A) and the chemical reaction of maltose and water to form glucose (B) (© 2019 Let’s Talk Science using images from NEUROtiker via Wikimedia Commons - Amylose, Maltose and Glucose).

What are hops?

Next, the brewer adds hops to the wort. Hops are flower buds from the female hop vine. Within these buds are chemical compounds called resins. They give some beers their bitterness and aroma. In order to extract the bitter resins from the hops, the wort must be boiled. This way, the hops become soluble and dissolve into the wort. By playing around with the amount of hops, you can control just how bitter (or “hoppy”) the beer will be.

Did you know?

Before the invention of modern refrigeration, hops were used as a preservative in beer.

Hop vine flowers/Inflorescences florales du houblon
Photograph of flower buds from the hop vine (Source: Hagen Graebner [CC BY-SA 2.5] via Wikimedia Commons).

What is fermentation?

Finally, the brewer adds yeast. Yeast is a single-celled organism that feeds on sugar. It is added to the sweet, hoppy mixture. There, it rapidly breaks down sugars, releasing carbon dioxide and alcohol.

Fermentation of glucose by yeast
Fermentation of glucose by yeast to form ethanol and carbon dioxide (© 2019 Let’s Talk Science using image from NEUROtiker via Wikimedia Commons).

This process is called fermentation. It ends when the yeast has consumed almost all of the sugar. After fermentation, the yeast is collected and reused for the next batch of beer

Did you know?

Alcohol has a lower boiling point than water. Alcohol boils at about 78.2 to 78.4 °C, while water boils at 100 °C. To make non-alcoholic beer from regular beer, you simply have to boil off the alcohol.

How do different types of beer get their flavour?

The end product is a hoppy, carbonated, alcoholic drink called beer. The flavour and type of beer depends on the temperature, timing, and amount of each ingredient. For example, the main difference between the brewing process of ale and lager is the temperature at which fermentation takes place.

Variety of beers/Types de bières
Photograph of a variety of beers (Source: Personal Creations (www.personalcreations.com) [CC BY 2.0] via Wikimedia Commons).

The most important ingredient, however, is yeast. It helps make sure the same brand of beer has a consistent flavour. Breweries that make the same beer over and over must use the same strain of yeast. Most breweries will happily give out their recipes. That is because without their specific strain of yeast, you can’t replicate their beer. In fact, breweries are extremely protective of their yeast strain. They often store a backup supply off-site in case their main supply gets contaminated. 

What if there is a mutation in the yeast - that is, a change in its DNA? This can create a strain of yeast so different from the original it would be like comparing two different breeds of dogs. Mutated yeast will produce a beer that tastes completely different from the original. It might even taste bad!

Beer might seem like a simple beverage that many adults like to drink. But now you have an idea of just how much science goes into it. Cheers to that!
 

Starting Points

Connecting and Relating

  • Does anyone in your family make beer or wine? If so, what type do they make?
  • Have you ever used yeast to make something you can eat? What role did yeast play in the food you were creating?
     

Connecting and Relating

  • Does anyone in your family make beer or wine? If so, what type do they make?
  • Have you ever used yeast to make something you can eat? What role did yeast play in the food you were creating?
     

Relating Science and Technology to Society and the Environment

  • Fermentation is a chemical process that produces alcohol. How has the production of alcohol had both positive and negative impacts on society? 
  • Why do governments have laws and licensing procedures to control who is permitted to produce alcohol? Explain.
  • Are there any byproducts of the brewing industry? If so, what are they and how are they used? (This question may require additional research.)
     

Relating Science and Technology to Society and the Environment

  • Fermentation is a chemical process that produces alcohol. How has the production of alcohol had both positive and negative impacts on society? 
  • Why do governments have laws and licensing procedures to control who is permitted to produce alcohol? Explain.
  • Are there any byproducts of the brewing industry? If so, what are they and how are they used? (This question may require additional research.)
     

Exploring Concepts

  • What is saccharification and why is it important in the fermentation process?
  • Explain, using chemical equations, the processes by which starches are broken down into sugars and sugars are broken down to release alcohol.
  • Why is yeast such an important ingredient in the beer-making process? How can the quality of yeast impact on the process and final product? 
  • What other ingredients are used to give beers their distinctive flavours?
  • What other foods do we eat that are fermented? What are the human health benefits of fermented foods? (This question may require additional research.)
     

Exploring Concepts

  • What is saccharification and why is it important in the fermentation process?
  • Explain, using chemical equations, the processes by which starches are broken down into sugars and sugars are broken down to release alcohol.
  • Why is yeast such an important ingredient in the beer-making process? How can the quality of yeast impact on the process and final product? 
  • What other ingredients are used to give beers their distinctive flavours?
  • What other foods do we eat that are fermented? What are the human health benefits of fermented foods? (This question may require additional research.)
     

Nature of Science/Nature of Technology

  • Most North American brewers use their supply of yeast only 10-12 times and then replace it with a culture sent from their head office lab. What reason(s) would they have for doing this?
     

Nature of Science/Nature of Technology

  • Most North American brewers use their supply of yeast only 10-12 times and then replace it with a culture sent from their head office lab. What reason(s) would they have for doing this?
     

Media Literacy

  • How does popular media portray beer and beer drinking? 
  • Beer products tend to be heavily advertised. Beer companies also sponsor numerous public events, particularly sporting events. Why is there such an emphasis on advertising and sponsorship of beer? How do microbreweries differentiate their products from that of the major brewing companies? 
     

Media Literacy

  • How does popular media portray beer and beer drinking? 
  • Beer products tend to be heavily advertised. Beer companies also sponsor numerous public events, particularly sporting events. Why is there such an emphasis on advertising and sponsorship of beer? How do microbreweries differentiate their products from that of the major brewing companies? 
     

Teaching Suggestions

  • This article can be used for Chemistry and Biology teaching and learning related to biochemistry and fermentation. Concepts introduced include biochemical reactions, alcohol, barley, germination, malt, enzymes, proteins, saccharification, wort, hops, yeast, fermentation and mutation.
  • Before reading the article, teachers could provide students with a Vocabulary Preview to access prior knowledge and introduce new terminology. Download ready-to-use reproducibles using the Vocabulary Preview learning strategy for this article in [Google doc] and [PDF] and formats.
  • This article could be used as an introduction to various hands-on science inquiries or experiments involving fermentation reactions. For example, students could compare how the amount of sugar added to yeast impacts on the production of carbon dioxide (C02) in a fermentation reaction. This video Fermentation of Yeast & Sugar - The Sci Guys: Science at Home provides one idea for a simple inquiry that students could conduct.
  • Teachers could also have students make a fermented food and learn about the different types of fermented foods and their origins (e.g., yogurt, kefir, sauerkraut, kombucha, natto, kimchi).
     

Teaching Suggestions

  • This article can be used for Chemistry and Biology teaching and learning related to biochemistry and fermentation. Concepts introduced include biochemical reactions, alcohol, barley, germination, malt, enzymes, proteins, saccharification, wort, hops, yeast, fermentation and mutation.
  • Before reading the article, teachers could provide students with a Vocabulary Preview to access prior knowledge and introduce new terminology. Download ready-to-use reproducibles using the Vocabulary Preview learning strategy for this article in [Google doc] and [PDF] and formats.
  • This article could be used as an introduction to various hands-on science inquiries or experiments involving fermentation reactions. For example, students could compare how the amount of sugar added to yeast impacts on the production of carbon dioxide (C02) in a fermentation reaction. This video Fermentation of Yeast & Sugar - The Sci Guys: Science at Home provides one idea for a simple inquiry that students could conduct.
  • Teachers could also have students make a fermented food and learn about the different types of fermented foods and their origins (e.g., yogurt, kefir, sauerkraut, kombucha, natto, kimchi).
     

Learn more

The Very Interesting History of Beer

An article from Mentalitch covering the history of beer. Article contains an additional video (12:40 min.) on the history of beer.

Brew a Great Non-Alcoholic Beer

An article by John Naleszkieqicz with instructions on how to brew non-alcoholic beer.

References

All About Beer Magazine. (n.d.). Malt.

Nice, K. (2000, December 12). How beer works. HowStuffWorks.

Kate Williams

Kate Williams is currently working on her PhD in Neuroscience at McMaster University.  Her research focuses on how the brain changes during development and aging.  In her spare time she enjoys traveling, reading, running, and playing softball.

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