yeast
Definition
Yeast is a single-celled fungus that is classified as a member of the kingdom Fungi. It is a eukaryotic organism, meaning that its cells have a nucleus and other membrane-bound organelles.
Yeast cells are typically oval or round and can be seen with a microscope. They reproduce by budding, which is a process in which a new cell grows out of an existing cell.
Yeast cells need food and water to grow. They also need a warm environment. The ideal temperature for yeast growth is between 80 and 90 degrees Fahrenheit.
Yeast is used in a variety of applications, including baking, brewing, and winemaking. In baking, yeast is used to make bread rise. The carbon dioxide gas that yeast produces causes the dough to expand, creating a light and airy loaf of bread.
In brewing, yeast is used to ferment wort, which is a mixture of water, malted barley, and hops. The yeast converts the sugars in the wort into alcohol and carbon dioxide. This is what gives beer its characteristic flavour and fizz.
Yeast is also used to make wine. The process of winemaking is similar to brewing, but winemakers use different types of yeast and grapes.
How can the word be used?
The yeast was used to ferment the beer.
Different forms of the word
Noun: yeast (plural: yeasts).
- a single-celled fungus that can ferment carbohydrates.
- a leavening agent.
Adjective: yeasty.
Verb: to yeast.
- to ferment with yeast.
Etymology
The word "yeast" comes from the Old English word "gist", which means "foam" or "froth". The Old English word "gist" is related to the Old Norse word "gista" and the German word "Geste".
The word "yeast" is first attested in the 13th century. It was originally used to refer to the foam or froth that forms on top of fermenting liquids.
The modern meaning of the word "yeast" refers to a single-celled fungus that is used to make bread, beer, and wine. Yeast is a type of microorganism that can reproduce rapidly by budding. When yeast cells reproduce, they release carbon dioxide gas, which causes the dough to rise.
Question
What yeast used for?
AQA Science Exam Question and Answer
Question:
Explain the role of yeast in fermentation processes and its significance in food production. Discuss how yeast converts sugars into alcohol and carbon dioxide, providing an example of a product resulting from yeast fermentation.
Answer:
Yeast is a microorganism that plays a crucial role in various fermentation processes, particularly in the production of foods and beverages. One of the significant contributions of yeast is its ability to convert sugars into alcohol and carbon dioxide through the process of fermentation.
During fermentation, yeast enzymes break down sugars into simpler molecules, primarily ethanol (alcohol) and carbon dioxide. This metabolic process occurs in the absence of oxygen, making it anaerobic. The carbon dioxide produced is responsible for the characteristic rising of dough in bread-making and the effervescence in carbonated beverages.
A classic example of yeast-driven fermentation is the production of bread. When yeast is added to bread dough, it consumes the sugars present in the flour, producing carbon dioxide gas as a byproduct. The trapped gas forms bubbles, causing the dough to rise and giving the bread its light and airy texture when baked.
Beyond bread, yeast fermentation is also instrumental in brewing beer, fermenting wine, and producing other alcoholic beverages. Yeast's transformative capabilities contribute to the development of a wide range of foods and drinks, enriching our culinary experiences and traditions.