Yeast 101: The Funnest Fungus, Part 2

I get asked a lot which homebrew stores I like to get my supplies from. In fact, price there was recently a good discussion on LinkedIn that got me started thinking more about this topic. Usually, cough as consumers, endocrinologist we can tell a good store from a bad one, and for homebrew stores the rules are more or less the same as they are at your local supermarket. Here in the DC area I have my choice of three stores I can visit almost any day of the week: My Local Homebrew Shop, Maryland Homebrew, and Annapolis Homebrew. All three stores are what I would call good places to get supplies and advice.

Here are some qualities I think make a store good:

  • Refrigerated ingredients. If you see hops sitting on a shelf unrefrigerated, turn tail and leave. The same goes for yeast, obviously. Hops have very volatile oils whose spoilage loses the unique characteristics of the particular hops strain. These should always be refrigerated.
  • Climate-controlled grain storage. Dried grain can last a long time in various temperatures, but this is not ordinary grain you might make into bread. The delicate taste of the particular roast and the stability of the sugar content is all aided by a good climate control system.
  • Clean packages. Whether it’s a can of malt extract or a bag of bottle caps, keeping the merchandise clean is a general indication that the retailer cares about the image he or she presents.
  • No old products. Have you ever seen something in a store that was in an old, yellowed

However, I have been to less-than-ideal stores.

troche
on Flickr”>Nuclei in yeastAlong with malt, water, and hops, yeast is one of the four necessary pillars of beer. Each element adds its own unique set of characteristics to the beer, though the influence of yeast is often misunderstood. Ensuring the right conditions for the fermentation process is overlooked by many homebrewers, which can often lead to an unhappy batch of beer. Unleashing the full potential in your beer can be that extra bit of magic that turns a mediocre batch of beer into a great one.

First, a little yeast basics. Yeast is a fungus. More specifically, it is a single-cell organism that got stuck in its evolutionary development somewhere between an animal and plant. The individual yeast cell has characteristics similar to a plant cell, such as a cell wall. Unlike most plant cells, it has no chlorophyll to help produce sugars from carbon dioxide and sunlight. There are many different varieties of yeasts, but the ones that are of importance in the beer world consume sugars located in their immediate environment to produce carbon dioxide and ethyl alcohol in a process called fermentation. In order to metabolize these sugars, the yeast cell requires oxygen, like an animal cell.

There are two types of yeast that are of primary concern to homebrewers: Ale and Lager yeast. Among these two types are many strains that have been crafted over the centuries to produce a variety of subtle flavors which have become cornerstones of many beer styles.

The scientific name for Ale yeast is Saccharomyces cerevisiae (or just S. cerevisiae). These are typically characterized by being top -fermenting yeasts, in that they hang around the top of the fermenter, and prefer warmer temperatures, around 60 to 70 degrees Fahrenheit. The warm temperature allows for a quicker fermentation period. The yeast will consume the majority of fermentable sugars in a five-gallon batch of beer in between 3 to 5 days. Also as a result of the warmer fermentation temperatures, Ale yeasts tend to produce complexity of flavors, particularly fruity and flowery (estery) flavors.

The Lager yeast's scientific name is Saccharomyces uvarum (S. uvarum). Lager yeasts are bottom fermenting yeasts that prefer colder temperatures between 38 and 50 degrees Fahrenheit. The colder temperatures greatly slow down the fermentation process, so fermentation can take months. The long wait is worth it. The product of this long fermentation is a clean, clear, and crisp beer without the fruity and estery flavors notable in Ales.

In the fermentation process, yeast will take in some oxygen, then use that oxygen to metabolize sugar into carbon dioxide and ethyl alcohol. Once the yeast cell gathers enough energy, it will clone itself by splitting into two new yeast cells. This process repeats itself until the yeast either runs out of oxygen and sugars and begins to flocculate (clump in groups) falling to the bottom as sediment, or the levels of alcohol become too high, at which point the yeast cells become drunk and quit their jobs.

In Part 2, we will go over the necessary conditions that influence yeast in the fermentation process to produce the best results. Until then…

Nuclei in yeast by TheJCB

Along with malt, denture
water, medicine
and hops, yeast is one of the four necessary pillars of beer. Each element adds its own unique set of characteristics to the beer, though the influence of yeast is often misunderstood. Ensuring the right conditions for yeast in the fermentation process is overlooked by many homebrewers and can often lead to an unhappy batch of beer. Unleashing yeast's full potential in your beer can be that extra bit of magic that turns a mediocre batch of beer into a great one.

First, a little yeast basics. Yeast is a fungus. Well, a yeast cell is a fungus, yeast are fungi. More specifically, yeast is a single-cell organism that got stuck in its evolutionary development somewhere between an animal and plant. The individual yeast cell has characteristics similar to a plant cell, such as a cell wall. Unlike most plant cells, yeast has no chlorophyll to help produce sugars from carbon dioxide and sunlight. There are many different varieties of yeasts, but the ones that are of importance in the world of beer consume sugars located in their immediate environment to produce carbon dioxide and ethyl alcohol in a process called fermentation. In order to metabolize these sugars, the yeast cell requires oxygen, like an animal cell.

There are two types of yeast that are of primary concern to homebrewers: Ale yeast and Lager yeast. Among these two types are many strains that have been crafted over the centuries to produce a variety of subtle flavors which have become cornerstones of many beer styles.

The scientific name for Ale yeast is Saccharomyces cerevisiae (or just S. cerevisiae). Ale yeasts are typically characterized by being top -fermenting yeasts, in that they hang around the top of the fermenter, and prefer warmer temperatures, around 60 to 70 degrees Fahrenheit. The warm temperature allows for a quicker fermentation period. The yeast will consume the majority of fermentable sugars in a five-gallon batch of beer in between 3 to 5 days. Also as a result of the warmer fermentation temperatures, Ale yeasts tend to produce complexity of flavors, particularly fruity and flowery (estery) flavors.

The Lager yeast's scientific name is Saccharomyces uvarum (S. uvarum). Lager yeasts are bottom fermenting yeasts that prefer colder temperatures between 38 and 50 degrees Fahrenheit. The colder temperatures greatly slow down the fermentation process, so fermentation can take months. The long wait is worth it. The product of this long fermentation is a clean, clear, and crisp beer without the fruity and estery flavors notable in Ales.

In the fermentation process, yeast will take in some oxygen, then use that oxygen to metabolize sugar into carbon dioxide and ethyl alcohol. Once the yeast cell gathers enough energy, it will clone itself by splitting into two new yeast cells. This process repeats itself until the yeast either runs out of oxygen and sugars and begins to flocculate (clump in groups) falling to the bottom as sediment, or the levels of alcohol become too high at which point the yeast cells become drunk and quit their jobs.

In Part 2, we will go over the necessary conditions that influence yeast in the fermentation process to produce the best results. Until then…

 

Along with malt, pill
water, and hops, yeast is one of the four necessary pillars of beer.  Each element adds its own unique set of characteristics to the beer, though the influence of yeast is often misunderstood.  Ensuring the right conditions for yeast in the fermentation process is overlooked by many homebrewers and can often lead to an unhappy batch of beer.  Unleashing yeast's full potential in your beer can be that extra bit of magic that turns a mediocre batch of beer into a great one.

 

First, a little yeast basics.  Yeast is a fungus.  Well, a yeast cell is a fungus, yeast are fungi.  More specifically, yeast is a single cell organism that got stuck in its evolutionary development somewhere between an animal and plant.  The individual yeast cell has characteristics similar to a plant cell, such as a cell wall.  Unlike most plant cells, yeast has no chlorophyll to help produce sugars from carbon dioxide and sunlight.  There are many different variety of yeasts, but the ones that are of importance in the world of beer consume sugars located in their immediate environment to produce carbon dioxide and ethyl alcohol in a process called fermentation.  In order to metabolize these sugars, the yeast cell requires oxygen, like an animal cell.  

 

There are two types of yeast that are of primary concern to homebrewers: Ale yeast and Lager yeast.  Among these two types are many strains of yeast which have been crafted over the centuries to produce a variety of subtle flavors which have become corner stones of many beer styles.  

 

The scientific name for Ale yeast is Saccharomyces cerevisiae (or just S. cerevisiae).  Ale yeasts are typically characterized by being top fermenting yeasts (hang around the top of the fermentor) which prefer warmer temperatures around 60 to 70 degrees Fahrenheit.  The warm temperature allows for a quicker fermentation period.  The yeast will consume the majority of fermentable sugars in a five gallon batch of beer in between 3 to 5 days.  Also as a result of the warmer fermentation temperatures, Ale yeasts tend to produce complexity of flavors, particularly fruity and flowery (estery) flavors.

 

The Lager yeast's scientific name is Saccharomyces uvarum (S. uvarum).  Lager yeasts are bottom fermenting yeasts which prefer colder temperatures between 38 and 50 degrees Fahrenheit.  The colder temperatures greatly slow down the fermentation process, so fermentation can take months.  The long wait is worth it.  The product of this long fermentation is a clean, clear, and crisp beer without the fruity and estery flavors notable in Ales.

 

In the fermentation process, yeast will take in some oxygen then use that oxygen to metabolize sugar into carbon dioxide and ethyl alcohol.  Once the yeast cell gathers enough energy, it will clone itself by splitting into two new yeast cells.  This process repeats itself until the yeast either runs out of oxygen and sugars and begins to flocculate (clump in groups) falling to the bottom as sediment, or the levels of alcohol become too high at which point the yeast cells become drunk and quit their jobs.  

 
In Part 2, we will go over the necessary conditions that influence yeast in the fermentation process to produce the best results.  Until then…

this web
on Flickr”>YeastIn Part 1, we went over some yeast basics and characteristics of Ale and Lager yeast as a very simple overview of the fermentation process. In Part 2, we will go over how understanding the right conditions for fermentation will maximize the good flavor potential of the yeast and, just as important, minimize the bad flavor potential. The primary factors are temperature, oxygen, the amount of fermentable sugars, the amount of yeast pitched, and viability of the yeast.

It is important to stay within the temperature range of the variety used during the fermentation period. Too far above the temperature range and the yeast can produce a variety of exciting flavors, almost all of which taste bad. Too far below and the yeast may just sit there and do nothing. Especially with Ales, too high of a temperature can set the right conditions for bacteria to beat the yeast to the sugars, which can contaminate the batch.

Oxygen is a factor that a lot of homebrewers forget about. Prior to pitching the yeast, it is important to agitate the wort or use a beer stone (air stone) to dissolve oxygen in the wort. Gasses, like oxygen, dissolve better at lower temperatures and the heat of the brewing process depletes much of the oxygen dissolved in the wort. Therefore, it is best to let the wort cool to the required temperature before stirring, shaking, or otherwise agitating the wort to dissolve the necessary oxygen.

The more fermentable sugars in the wort, the higher the potential alcohol content of the finished beer. The desired alcohol content is an important consideration in choosing which yeast variety to use. Ale and Lager yeasts do not tolerate high levels of alcohol well. They will usually keep fermenting until the alcohol level reaches about 8.5%. Around this point the yeast can become stressed and produce undesirable flavors and aromas as they stagger away drunk. For beer styles that have a higher than 8.5% Alcohol by Volume percentage (% ABV), it is best to use a yeast variety that has a higher alcohol tolerance, such as special strains for brewing yeast or even champagne yeast.

When determining how much yeast to pitch into the wort, it is better to pitch too much than too little. Too little can cause a prolonged lag time, giving other beasts, like bacteria, the edge to beat the yeast for dominance of the sweet sugars. Ideally the lag time between pitching the yeast and the yeast being thoroughly engaged in the fermentation process should not be more than a day. Worrying about the amount of yeast to pitch only really comes into play with homebrewers who culture their own yeast or for recipes with high specific gravity wort (more fermentable sugars) where the risk of contamination is slightly higher. Most commercially purchased yeast varieties, whether dry or liquid, are more than enough for a typical five-gallon batch. Be sure to follow the directions for preparing the yeast carefully to ensure the yeast get a good start. For high specific gravity beers, seriously consider making a yeast starter or doubling the amount of yeast pitched. Carl will be talking about yeast starters in a future post, hopefully soon.

Yeast viability is not much of an issue with commercially purchased varieties, as long as it is stored properly and used before the expiration date. Similar to determining the amount of yeast to pitch, viability only really becomes a factor for those who culture their own variety of yeast or harvest it from their favorite commercial beer. Old, tired, and/or mutated yeast can inhibit a clean fermentation process and produce a lot of uncharacteristic bad flavors.

Regardless of the variety of yeast you choose to craft your beer, it is important to give the little guys the right environment to maximize their career potential. Though the flavor impact of yeast on beer is often less subtle than its hops or malt counterparts, it can give a beer the flavor edge it needs to be great. Happy brewing!

Yeast by Chris Campbell

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