Is Ale Yeast a Bottom Fermenting Yeast? And Why It Matters

Most people, when thinking of beer, do not bother wondering whether their beer is an ale or a lager. Many don’t even know the difference. Many more might think it comes down to color or even alcohol content. Nothing could be further from the truth.

The difference between ales and lager is all in the yeast. One is made with a top fermenting yeast and the other is made with a bottom fermenting yeast. But what does this all mean anyway? And which is which? If you’ve been wondering if ale yeast is a bottom fermenting yeast, you’ll find your answer here, and more.

What Is Ale?

First, let us begin with the history of beer, which is really the history of ale. All beers, it is important to note, are either ales or lagers. But ales came first, by a mile.

Indeed, ales came even before bread.

The way it most likely happened was that someone drank a liquid that came from a grain sitting in water for a while. After a few days, that water attracted yeast, which is literally everywhere at all times, and the grain water became ale. The first beer.

Ale is both easy and fast to make.

All it takes is a grain, usually barley, which is malted, meaning put through a germination process that helps it develop more sugar. That grain is then cracked or ground to allow access to that sugar. The cracked grain is then boiled and steeped in water to release all those sugars. The liquid you now have is wort.

Traditionally, the wort was just left out for a few days. The yeast in the environment was naturally attracted to the sugar in the water, and it went to town eating up all that sugar and converting it to alcohol and carbon dioxide.

Today, the yeast is actually added, the wort is deprived of oxygen to keep the yeast fermenting, and hops are added later for flavor and bitterness.

But originally, the yeast would sit on the surface of the ale and even form a crust on top, often called a krausen. When the ale was complete, the crust would be scraped off to make another batch of ale, or even to make bread.

Ale Yeast Is a Top Fermenting Yeast

Thus, ale yeast is a top fermenting yeast. That means the yeast attracted to the wort left out in the warm air fermented the wort from the surface.

This specific yeast, we now know, is a form of brewer’s yeast called Saccharomyces cerevisiae. It tends to ferment best at warmer temperatures, ranging from 50 degrees to 70 degrees Fahrenheit, and it releases what are known as esters along with the alcohol and carbon dioxide. Those esters are what give ale a fruitier flavor than lagers.

Lager Yeast Is a Bottom Fermenting Yeast

Lager yeast, then, is the bottom fermenting yeast.

Lagers were not discovered until many hundreds of years after ales, and only accidentally, much like the discovery of ales.

A group of Bavarian monks making beer in the 1400s were delighted to discover they could make beer year-round. At first, they could only make beer in cooler weather as the beer would go bad after a few days, the yeast would get too warm and die out, stopping the fermentation process, and bacteria would get into the beer, giving it off flavors.

Introducing Brett

Those off flavors the monks were trying to avoid arose as a result of a yeast that loves to insert itself into the warmer temperature worts and beers. Brettanomyces, or Brett for short, is a yeast both welcomed and avoided over the last several centuries of beer making. It is the wild yeast often referred to in sour beers, and that same yeast can ruin an entire batch of beer by making it taste like sour milk or baby vomit. Because of its unpredictable returns, most brewers, including those monks, sought to avoid it.

Thus, when the monks discovered they could store the ale in caves and keep it much cooler, allowing them to make beer year-round, they also discovered a new kind of yeast that was attracted to cooler temperatures as well.

Introducing Saccharomyces Pastorianus

This new yeast, S. pastorianus, prefers dark, cool liquid in which to ferment, thriving at temperatures between 35 degrees and 50 degrees Fahrenheit. It also takes much longer to ferment, taking its sweet time converting all those sugars into alcohol and carbon dioxide. In fact, it creates less carbon dioxide at those cooler temperatures than its cousin the ale yeast. Lagers take up to 8 weeks to complete fermentation, while ales only take 3 to 5 weeks. As it ferments, it drops to the bottom of the vessel and does most of its work there, comfortable in the dark cool caverns of what will become lager.

The Rise and Fall of Ales and Lagers

Still, it took another couple of hundred years for lagers to really catch the attention of global beer drinkers. It was German brewers who introduced “pilsners” in the 1800s, and the new, crisp, clear beverage took off.

Sadly, the lager has fallen into disrepute of late. This bottom fermenting beer has been watered down by many beer companies, leaving many beer drinkers to turn faithfully back to ales for their richer, fuller bodied flavors.

Today, with the rise of small craft breweries, you can find both ales and lagers with superior and complex flavors. And, it must be noted, both ales and lagers can have their fermentation and aging processes extended for even more depth and complexity. The wonders and magic that brewers can create with bottom fermentation, top fermentation, hops, and additional fruits and even bacteria will amaze even the most experienced beer drinker. It seems there can never be too much variety when it comes to beer.

Passionate about the beer and/or wine making process? So are we! If you’re interested in finding out how you can use our technology to control fermentation and monitor your yeast, save work hours and improve the cost-efficiency of your business, drop us a line at [email protected] or check out our product pages:

Also, you can now get access to a fully functional demo account to test our Web App. Completely free of charge and with no commitment to purchase.

Sources:

  1. Andrea Pavsler, Stefano Buiatti, Beer in Health and Disease Prevention, 2009, Pages 31-43
  2. https://www.thebrewenthusiast.com/yeast
  3. https://beerandbrewing.com/dictionary/2Kudv5620R/
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