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For all brewers, the issue of consistency is a critical one. This article explores the role yeast analysis plays in brewing, and why it matters. While most brewers understand what yeast does in beer, many do not realize the importance of keeping a constant, ongoing, and accurate count of their yeast cells both throughout the brewing process and in between batches.
Yeast analysis in brewing is something every brewer should be doing. It is certainly being done at the giant corporation level, so if craft brewers hope to gain traction and keep it, to grow their fan base and spread the word about their amazing beer, yeast analysis is a critical factor.
It all comes down to consistency.
To recap what you likely already know, the role of yeast in beer is perhaps the most important role any ingredient plays in the entire production.
Without yeast, you would just have grain water, some sort of oatmeal.
Early Beer, Less Consistency
Indeed, that is likely how beer was discovered. Someone hundreds and hundreds of years ago left out some grain, the grain got wet, and wild yeast collected and fermented that wet grain. Someone very brave then decided to either eat the wet grain or drink the liquid. Et voila. You have the very first ale.
Over time, beer production became as simple as that. Brewers would boil grain, usually barley or wheat, leave it to ferment, a mysterious process they knew little about, and they would sell the resulting product to passerby in pubs, inns, taverns. Beer was also being brewed in monasteries. Indeed, the first lager was likely made by monks who discovered the cooler temperature loving yeast that produces lager.
The only consistency these early brewers could rely on was based on the fact that they used the same grain, the same process, and did it in the same location. The beer came out tasting mostly the same.
Science and Beer
In the 1800s, however, Louis Pasteur, famed French chemist and microbiologist, actually studied the process of fermentation and discovered the role yeast plays.
He noted that vital, viable yeast, these living organisms, consume the sugars in the grain water and covert those sugars to ethanol (alcohol), carbon dioxide, and other nutritional byproducts that affect flavor and aroma.
As brewers caught wind of this scientific discovery, they began to utilize yeast more effectively, control it, and contain it.
The thing that makes Budweiser, Miller, Corona, Hefeweizen, Heineken, and any other major beer label successful is consistency. Fans of this or that beer love it because they not only love the flavor of the beer, but also they know they can rely on the fact that the beer will taste the same every single time they open the bottle.
Yeast is the key to consistency in your beer.
Now, it takes much more than simply using the same strain of yeast every time, though that part is important, of course; yeast affects protein, flavor, and aroma in beer.
It also, and perhaps more importantly, takes keeping an accurate count of yeast cells, as well as of the viability and vitality of your yeast.
Many brewers rely on the re-pitch process, meaning they can use the same batch of yeast over and over, up to ten times, to brew a new batch. Simply skim or filter out the yeast once the beer is done fermenting, and pitch it into your next batch of beer.
The problem is that, with each re-pitch, there are less and less viable yeasts (basically alive cells) and the vitality of the yeast cells may also be affected. When this happens, the fermentation process takes longer, and the consistency of flavor and aroma will eventually be less reliable. So to be able to reuse your yeast efficiently, without affecting your product, you have to be able to assess your yeast cell count, yeast viability and, ideally, yeast vitality.
Let’s take a minute to define the terms we’re using here.
When we talk about yeast cell count, we are simply referring to the concentration of yeast cells within a batch. When you measure, you are taking a small amount of the yeast and counting how many yeast cells are in that small amount, from which, of course, you can extrapolate to the entire batch.
Viability may, at least sometimes, be even more important than yeast cell counting because testing your yeast viability will tell you how many of those cells are actually alive. This information is critical when it comes to brewing because only living yeast cells can ferment your wort. Yeast that does not have high viability (meaning that a too small percentage of the yeast cells are actually alive) can cause stuck fermentation, which just makes more work for the brewer and may even lead to losing an entire batch. Also, the general consensus is that, in order to be able to reuse the yeast efficiently, the yeast viability has to be no lower than 90%.
And finally, yeast vitality: how strong and active the yeast cells are. You can have a lot of living yeast cells, but after a few too many re-pitches, those cells might start to slow down their activity. This will affect both the fermentation process and the ultimate flavor and aroma profiles.
In the end, you want to be able to do yeast cells counts, measure yeast viability and, ideally, yeast vitality both between batches and during fermentation so you can calculate and keep track of how well your yeast is performing and make decisions related to your consistency accordingly.
Yeast Cell Counting Methods: The Old Way vs The New Way
You can typically do yeast cell counts on your own with a hemocytometer. You may even be able to make some assessments regarding yeast viability. However, there is a learning curve involved, and the results may not always be accurate. Each individual’s eyesight is different and if there is more than one person doing the cell counts (through a microscope, on a hemocytometer), it is almost always required to readjust the focus and there is always the possibility of human error.
The good news is, though, that there have been significant advances made in the last years on developing technology that can help eliminate human error and make the whole cell counting process more efficient. The Oculyze Better Brewing App (developed by a German company), for instance, will not only count your yeast cells in a fraction of the time previously needed, but it also assesses yeast viability, has a pitch rate calculator and saves your history of analyses into the cloud for future access and comparison between batches.
Ultimately, the decision is entirely yours. However, no matter the methods you choose for counting your yeast and assessing its viability, you’ll need to do it consistently if you plan on making reliable promises to your loyal fan base in terms of the consistency in flavor and aroma they are pining for.