Hello lindzdoc-ga,
Making beer is a popular subject and I found lots of information
explaining the process. Several of the articles and resources listed
below will give you fully detailed explanations of the science of how
yeast is used in brewing beer. In very simple terms, yeast converts
carbohydrates into alcohol, carbon dioxide and various byproducts
through the process of fermentation. The information I?ve gathered
will help you explore this as deeply as you wish. Some of the articles
provide brief summaries while others go into great detail. Since
you?re on a tight deadline, you can pick and choose whatever suits you
best.
I trust that the research I?ve collected is sufficient but please
don?t hesitate to ask for clarification if anything needs further
explanation.
Best wishes for your project.
~ czh ~
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HOW TO MAKE BEER
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http://www.howtobrew.com/intro.html
How to Brew
Here is a synopsis of the brewing process:
1) Malted barley is soaked in hot water to release the malt sugars.
2) The malt sugar solution is boiled with Hops for seasoning.
3) The solution is cooled and yeast is added to begin fermentation.
4) The yeast ferments the sugars, releasing CO2 and ethyl alcohol.
5) When the main fermentation is complete, the beer is bottled with a
little bit of added sugar to provide the carbonation.
***** This is a book that is also available on this website. It gives
detailed instruction on the brewing process. You can follow the links
to get as much detail as you need. Chapter 8 on Fermentation addresses
the heart of your question of what is the process by which yeast
contributes to the making of beer.
http://www.howtobrew.com/section1/chapter8.html
Chapter 8 ? Fermentation
In this chapter, we will discuss fermentation - how the yeast turns wort into beer.
8.2 Re-defining Fermentation
The fermentation of malt sugars into beer is a complicated biochemical
process. It is more than just the conversion of sugar to alcohol,
which can be regarded as the primary activity. Total fermentation is
better defined as three phases, the Adaptation or Lagtime phase, the
Primary or Attenuative phase and a Secondary or Conditioning phase.
The yeast do not end Phase 2 before beginning Phase 3, the processes
occur in parallel, but the conditioning processes occur more slowly.
As the majority of simple sugars are consumed, more and more of the
yeast will transition to eating the larger, more complex sugars and
early yeast by-products. This is why beer (and wine) improves with age
to a degree, as long as they are on the yeast. Beer that has been
filtered or pasteurized will not benefit from aging.
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http://www.yeastgenome.org/ArtOfBrewing.htm
The Art of Brewing and the Biology of Lager Yeast
***** This is a 49-slide PPT presentation from the Miller Brewing
Company that gives a complete and detailed description of the beer
brewing process. It includes excellent diagrams and illustrations.
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http://www.beer-brewing.com/ch13-beer-fermentation.htm
Chapter 13 ? Beer Fermentation
Fermentation is the process by which fermentable carbohydrates are
converted by yeast into alcohol, carbon dioxide, and numerous
byproducts. The byproducts have a considerable effect on the taste,
aroma, and other characteristic properties of the beer. Fermentation
is dependent upon the composition of the wort, the yeast, and
fermentation conditions.
***** This is an excerpt from an online book. You can follow the links
to explore further about yeast and fermentation in brewing beer.
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http://realbeer.com/jjpalmer/Howtobrew.html
How to Brew Your First Beer
Brewing a beer is a combination of several simple processes. First is
the mixing of ingredients and bringing the solution (wort) to a boil.
Second is the cooling of the wort to the fermentation temperature.
Next the wort is transferred to the fermenter and the yeast is added.
After fermentation, the beer is siphoned off the yeast sediment and
bottled with a little extra sugar to provide the carbonation. These
are simple steps but there are three important things to keep in mind
every time you brew: Cleanliness, Preparation and Good Record Keeping.
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YEAST ? SACCHAROMYCES CEREVISIAE
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http://www.beertown.org/education/ingredients.html
Ingredients ? Yeast
Yeast makes beer by converting sugars from malt or malt extract into
alcohol and carbon dioxide. There are two major classes of yeast, ale
and lager. Ale yeast is a top fermenting yeast (meaning it is most
active near the surface of the fermenting beer) that ferments at
warmer temperatures, generally between 55 and 75 degrees F (13-24
degrees C). Ale yeast tend to produce fruity flavors and aromas, which
vary depending on the yeast. Lager yeast is a bottom fermenting yeast
(meaning it is most active near the bottom of the fermenting beer)
that ferments at colder temperatures, generally between 32 and 55
degrees F (0-13 degrees C). Lager yeasts tend to be neutral in flavor
and aroma and thus do not produce the fruity esters found in ale
yeasts. Beers fermented with lager yeasts are usually cold stored at
temperatures below 45 degrees F (7 degrees C) following primary
fermentation for a period of a few weeks to several months-a process
known as lagering. Beer yeast is sold in two forms, dried and liquid.
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http://www.yeastgenome.org/VL-yeast.html#edu
Yeast (Budding, Fission, and Candida)
This section of the Virtual Library describes the yeast model
organisms: Saccharomyces cerevisiae (budding, bakers', and sometimes
brewers'), Schizosaccharomyces pombe (fission), and Candida albicans.
***** This site offers a great collection of links for everything you
could want to know about yeast.
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http://www.yeastgenome.org/
Saccharomyces Genome Database
SGDTM is a scientific database of the molecular biology and genetics
of the yeast Saccharomyces cerevisiae, which is commonly known as
baker's or budding yeast.
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http://www.yeastgenome.org/VL-what_are_yeast.html
What are yeasts?
The most well-known and commercially significant yeasts are the
related species and strains of Saccharomyces cerevisiae. These
organisms have long been utilized to ferment the sugars of rice,
wheat, barley, and corn to produce alcoholic beverages and in the
baking industry to expand, or raise, dough. Saccharomyces cerevisiae
is commonly used as baker's yeast and for some types of fermentation.
Yeast is often taken as a vitamin supplement because it is 50 percent
protein and is a rich source of B vitamins, niacin, and folic acid.
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http://www.brewery.org/brewery/library/yeast-faq.html
Yeast Information and Technique Resource
-- SECTION I: YEAST BEHAVIOR
-- SECTION II: Yeast Profiles
-- SECTION III: YEAST MANAGEMENT
***** This collection of resources discusses all aspects of the use of
yeast in beer making.
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http://www.breadworld.com/sciencehistory/science.asp
Fleischmann?s Yeast -- The Science Of Yeast
Yeast is a tiny plant-like microorganism that exists all around us -
in soil, on plants and even in the air. It has existed for so long, it
is referred to as ?the oldest plant cultivated by man?.
The main purpose of yeast is to serve as a catalyst in the process of
fermentation, which is essential in the making of bread.
While there are many types - or strains - of yeast, at Fleischmann?s,
our sole focus is on Saccharomyces cerevisiae. This is the yeast that
is most commonly used in making bread.
Getting a Closer Look
It was Louis Pasteur In 1859 who first discovered how yeast works:
· Yeast feeds on the starches in flour, producing carbon dioxide
· The carbon dioxide expands the gluten proteins in the flour
· The gluten proteins cause the dough (of which flour is a main
ingredient) to expand and rise
THE PRODUCTION OF YEAST
From one tiny yeast cell, tons of yeast can be produced.
Here?s how the process works: (See website)
FERMENTATION
When the yeast cells have increased many times, the fermentation stage
begins. (See website)
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http://65.61.159.93/SoY/index.html
Explore the Science of Yeast
http://65.61.159.93/SoY/story_2.html
The Story of Yeast
What Is Yeast?
The scientific name for one species of yeast is SACCHAROMYCES
CEREVISIAE, or sugar-eating fungus. This name is derived from the
Latin word "cerevisiae", which means "brewer".
Yeast cells digest food to obtain energy for growth. Their favorite
food is sugar in its various forms: sucrose (beet or cane sugar),
fructose and glucose (found in honey, molasses, maple syrup and
fruit), and maltose (derived from starch in flour).
The process, alcoholic fermentation, produces useful end products,
carbon dioxide and ethyl alcohol, which are released by the yeast
cells into the surrounding liquid. This is how alcoholic drinks are
produced from starch containing flours. For example, barley flour is
used for making beer and wheat, corn and other grains are used for
making whiskey.
http://65.61.159.93/SoY/manufacturing.html
The Manufacturing of Yeast
The manufacturing process for yeast can be likened to farming ? it
involves preparation, seeding, cultivation and harvesting.
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http://www.barrelhouse.com/yeast.html
Yeast
We didn't really come to appreciate the role played by yeast in
fermentation until the 19th century. Louis Pasteur first became famous
for studying the yeast used by European breweries, in an effort to
help them make better beer.
The yeast cells in the photograph at left (at extremely high
magnification) show how they reproduce by budding. You can just see
the beginnings of new buds on at least two of the cells in the photo.
Yeast is a pretty hardy organism, and it tended to stick in the
microscopic cracks and crevices of brewing equipment, which was
largely made of wood. Since there was always some yeast around from
the previous batch, it came back into activity with each new batch,
multiplied, and fermented the wort into beer.
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BREWING RESOURCES, PORTALS, DIRECTORIES, ASSOCIATIONS
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http://www.beertown.org/aob/about.html
Association of Brewers (AOB)
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http://www.beerinfo.com/siteidx.html
The Beer Info Source
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http://www.realbeer.com/
Real Beer
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http://www.brewery.org/
The Brewery ? Total Homebrewing Information
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http://www.brewery.org/brewery/library/section_one
Technical Library at the Brewery
Technical articles on brewing-related topics.
***** This is a very comprehensive collection of links on all aspects
of brewing beer. See especially the sections on Yeast and
Fermentation.
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SEARCH STRATEGY
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Saccharomyces cerevisiae
how to brew beer
beer fermentation |
