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Brewing Brilliant Beer, Pt 3: Yeast Makes Beer

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This five-part series focuses on providing brewers with structures and tips to navigate the fundamental areas of the brewing process where the collective effect of a multitude of small decisions greatly impacts beer quality.

At the end of a brew day, the brewer surrenders their hard work to the yeast and fermentation begins. In this third article, we focus on the health and nutrition of the brewer’s chosen yeast.

Part 3 – Yeast Makes Beer

It is well known that healthy yeast makes better beer, thus the effort of the brewer must shift to providing the best possible environment in which the yeast can thrive.

Two key terms used to reference yeast health are viability and vitality. Viability refers to the number of cells that are ‘alive’, with vitality referencing the ‘health’ of these cells. Both have a direct impact on the yeast’s performance with vitality proving the true measure of health (it’s a given that a dead cell is not a healthy one!) Unfortunately, the vitality of yeast is more difficult to measure and consistently control.

The Benefits

Ensuring yeast is healthy throughout the fermentation has benefits across all aspects of your beer. Some are highly tangible, for example a broad reduction in off flavours, while others offer efficiency improvements such as shorter fermentation times and higher yields.

The countless reactions occurring within a yeast cell during fermentation take place in a delicate balance.

Unhealthy yeast struggles to maintain this equilibrium, leaving behind compounds that quickly have a negative impact on the taste and balance of the brew. Acetaldehyde, diacetyl and a wide spectrum of sulphur compounds are the commonly seen culprits in trade across the industry.

Maintaining high yeast vitality is essential to control these off-flavours.

As yeast health deteriorates, the efficiency of the fermentation also quickly falls, which in turn can impact operations across the brewery.

Healthy yeast will help save everyday brewery costs:

  • Increased fermentation kinetics – Faster fermentation increasing annual production capacity.
  • Improved flocculation – Shorter conditioning times mean reduced filtration costs.
  • Complete fermentation – Higher ethanol yields will help reduce ingredients costs.
  • Higher viability and vitality at end of fermentation – Greater suitability for re-pitching will lead to cost savings.

Basic Nutritional Needs

Achieving adequate nutrition is thankfully a relatively straightforward task.

An all-grain wort comprised from high quality malt provides all the key requirements for yeast metabolism, except for Zinc and Oxygen.

In a good wort you will find an abundance of Carbon (in the form of sugar), Nitrogen in various forms, along with the variety of vitamins and minerals essential for a vigorous and clean fermentation.

Zinc deficiency is a simple fix, supplemented via either a liquid solution of zinc sulphate (essentially pure Zinc), or a yeast ‘food’ complex that provides the missing zinc, whilst at the same time topping up trace minerals such as Manganese, Potassium and Phosphorous.

Whilst these latter elements do exist in sufficient levels in wort, a small boost to their concentration offers some safety against potential poor-quality malt.

The requirement for Oxygen is easily solved via injection directly to the wort stream on brew day. This Oxygen is used for the metabolism of sterols, required for healthy cell membrane structure during budding.

Keep in mind:
– Too much Zinc is toxic to yeast, so be sure to respect dosing rates for all nutritional additions.
– It is worth noting that there may be no need to oxygenate wort on the first pitch, when using certain dried yeast strains. Dried yeasts are produced in Oxygen-rich environments and consequently contain all the sterols required for cell growth during the first fermentation.
– When utilising adjunct sugar in the production of higher-alcohol beers, the basic nutritional needs of yeast are unlikely to be met without some form of supplementation.
– Over oxygenation instigates greater yeast growth, which means there are more cells trying to claim their slice of the available nutrients. This leads to deficiencies, even in all-grain wort.

Fermentation Environment

Yeast health depends on more than the physical building blocks it utilises for metabolism. There are many environmental factors that demand careful management to ensure that conditions remain within the tolerance ranges of the selected yeast.

Temperature and pressure are both well understood (and easily controlled) examples of these environmental influences. Steering either of these towards the limit capabilities of your selected yeast strain will quickly affect vitality, with viability lost completely when tolerances are exceeded.

Fermentation pH is another key environmental factor.

The ability to tolerate low or high pH is vastly different between strains. Whilst yeast cells can often survive highly acidic environments (such as acid washing), their vitality at low pH is halted, or at the very least, significantly reduced.

Keep in mind:
– Remove dead yeast from the bottom of your fermenters as frequently as possible. Some unviable cells are inevitable and the osmotic pressure at the bottom of the cone will quickly cause yeast autolysis. Rising pH at the end of fermentation is a sign that autolysis is occurring.
– If pitching additional dry yeast to a ferment, be sure to hydrate in fresh wort or water first. The dried cell membrane is delicate and easily damaged if exposed to an environment where alcohol is present during rehydration.
– Wort density, alcohol percentage, dissolved carbon dioxide and even the ratios of various chain sugars present in the wort are all interconnected in the balance of yeast health.

Getting it Right

The common solutions previously discussed of either pure zinc or yeast food are readily accessible and fit for purpose in the majority of beers.

Good yeast health will be achieved in an all-grain beer that isn’t pushing fermentation parameters to their limits if:

  • You start with a high quality (and thus initially healthy) yeast strain,
  • Prepare the advised concentration in the correct way, and
  • Dose at the right time in the brewing process.

As the recipe begins to dictate a more challenging ferment, be it by higher alcohol or heavy adjunct usage, further nutritional support is advised. Yeast producers have provided simple solutions for these fermentations, through the development of specialised nutrients that contain inactivated yeast.

The inactivated yeast provides everything yeast needs to grow, after all, it once was a thriving cell itself. Products such as SpringFerm™ BR-2 from Fermentis contain inactivated yeast, in conjunction with Zinc and Manganese for a total nutritional solution.

Keep in mind:
– A hidden benefit of all-grain malt is its excellent buffering capability. As you step into high adjunct brews, the pH can rapidly crash during fermentation and halt an otherwise healthy ferment.

Stepping Outside Normal

The rapid innovation of styles, ingredients and techniques brewers are using globally is bringing new challenges. It is no longer a case of one size fits all. For one, the rise of seltzer has proven just how difficult fermenting sugar in the absence of any nutrition can be.

Brewers must tailor their nutritional additions individually to each product as they innovate. Breaking down the beer in a few different aspects will help to highlight the challenges that lie ahead for the yeast and in turn direct you to the right solutions.

For example, consider the likely impact the following will have on yeast health:

  • the category (sour, fruited, seltzer, kombucha, cider etc),
  • the ingredients in play (specific fruits, adjuncts, alternate cereal grains etc.),
  • the target parameters (alcohol content, residual sugars, etc).

Thankfully, there is also an abundance of highly specialised nutritional supplements available that you can turn to when you begin to push the boundaries. These products have historically been used in fermentation industries outside of beer, finding their way into beer as brewers change the rules.

Yeast nutritional supplements are often highly targeted, calling on a combination of yeast fractions, cell lipids, partially to fully autolysed yeast cells, vitamins, minerals, buffering capabilities and more.

Keep in mind:
– Always keep the selected yeast front of mind as alternate strains may require a slightly different nutritional balance for optimum health on the same wort stream.
– Be prepared to change strains if it is proving difficult to give the original yeast the conditions it requires.

A Vital Alliance

You rely on yeast to transform your wort into a quality beer and thus must manage the fermentation environment and wort makeup to provide your chosen yeast with all the nutrition it needs.

High viability and vitality lead to better-tasting beer and a more efficient brewery.

With a multitude of research and innovative products freely available, there is no better time to put yeast health at the top of your brewery’s to-do list and get the processes in place to make consistently great beer.

You can find the first 2 articles in this series here:

Brewing Brilliant Beer, Pt 1: Getting Your Recipe Right

Brewing Brilliant Beer, Pt 2: Brewers Make Wort

 

This series is brought to you in partnership with

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Article by:

Justin Fox

Justin Fox

Justin hails from Melbourne and has 15 years experience in brewing, ingredient supply and beer judging. He is currently keeping busy (and hydrated) as the Australian agent for Bespoke Brewing Solutions, alongside running his own consultancy services.

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