Using Yeast Nutrients
When I was a kid, my grandma would buy sampler packs of single-serving boxes of Kellogg’s cereal for my brothers and me. Remember those? Invariably, the last one to get eaten was always Product 19 — the one with all the essential vitamins and minerals. Those nutrient-rich but sugar- and cartoon character-deficient flakes may have been the pariahs of the morning table, but they provided us with extra fortitude to jump on couches and race around the backyard for the rest of the day.
Maybe that’s a bit of an exaggeration (couches were going to get jumped on no matter what was for breakfast), but the same thing is going on at a cellular level in our fermentations: our yeast cells need their Product 19. In this elegant analogy, the couch and backyard represent the wort, the jumping around is fermentation, and the poorly-regarded-by-eight-year-old-me cereal is yeast nutrient.
Yeast Nutrient: A Working Definition
“Yeast nutrient” (sometimes even called “yeast food” in some texts) is a bit of a catchall for the various vitamins, minerals, ions, and other compounds required for cells to function properly in a fermentation — we’ll continue to use that umbrella term here. Basically, yeast nutrients help yeast reproduce to produce healthy cells. If yeast nutrient levels are deficient then the cell reproduction will be reduced and daughter cell health will be compromised. To help us keep it sorted out, here are some quick definitions:
Vitamin: An organic substance essential in small quantities for normal metabolism.
Mineral: A naturally-occurring and usually inorganic substance.
Ion: An electrically charged atom or group of atoms.
A number of enzymes within the yeast cell require these various nutrients in order to carry out the basic functions of life. The tricky part is that the right amount of nutrients can vary based on yeast strain, wort composition, and other batch-to-batch conditions. What’s more, too much of any one of these nutrients can become problematic for the fermentation and its resulting beer.
Real Talk: Do I Gotta?
Disclaimer up front: Most all-malt worts will contain almost everything a yeast cell needs in terms of vitamins and minerals. For that reason, given the beer styles which homebrewers and craft brewers commonly prefer to brew, most of the time it’s perfectly possible to turn out a good beer without tinkering with a nutrient addition.
Second Disclaimer: Fine-tuning wort nutrient levels isn’t as important as adding a healthy population of viable cells at an appropriate pitching rate, ensuring a proper fermentation temperature, and supplying the cells with adequate levels of O2 — our yeast wants us to see to that stuff first.
But having said that, here’s where an ounce of prevention really beats a pound of cure: high-gravity fermentations, grists with a high percentage of unmalted adjuncts, and when propagating yeast. And even in an all-malt wort, yeast cells may not be getting a well-rounded breakfast.
Ounce of Prevention #1: Chelation and Limited Availability
In an all-malt wort where all systems should be “go” in terms of yeast health, vital nutrients can be lost or made unavailable to the cells through normal brewing processes.
One example of this is chelation, which is the chemical term for a bond formed between a metal ion and another molecule. In the course of boiling wort, zinc — a vital component for the conversion of wort sugars to alcohol by the cells — can become bound to wort proteins and precipitated with the break material. Any beer wort will lose zinc to this process and may be deficient by the time it reaches the fermenter.
On top of that, an overabundance of one nutrient can limit yeast cells’ access to another nutrient. For example, calcium and magnesium are both important to cell function in a beer fermentation, helping to regulate flocculation and metabolism, respectively; but a high level of calcium ions will inhibit uptake of magnesium by the cells.
Supplementing the yeast nutrient content of even all-malt worts can help coax more performance out of our yeast pitches and maximize fermentations — as insurance goes, it’s pretty cheap.
Ounce of Prevention #2: Propagation and Stressful Fermentations
Any homebrew could fall victim to the decreased viability of a yeast pack that’s spent a long time in storage or in transit. In that situation, preparing a starter culture with the necessary environmental factors — malt sugars, oxygen, and nutrients — to help the cells recover and rebuild is the first critical step to a successful batch.
In any stressful fermentation — whether the high osmotic pressure and ethanol levels of a high-gravity fermentation, the nutrient-poor wort of a high-adjunct lite lager, or when culturing up depleted cells from a pack after storage or shipping — a few pennies’ worth of nutrient can fix problems before they start.
If you’re a brewer who’s already aware of the importance behind proper pitching rate and yeast health, fermentation temperature, and O2, then you’re aware of the cascading problems that a hiccup with those processes can create; in much the same way, a scarcity of nutrients can trigger its own cascade of woe.
Vitamins and minerals by definition can’t be created within the cell — they must be supplied by the environment. Without an adequate supply of the trace elements that help regulate some really basic functions of the yeast cell, brewers can experience sluggish or incomplete fermentations, low or inconsistent attenuation, and decreased viability.
Let’s Add Some Nutrient
Enough chemistry and scary what-ifs – let’s talk practicalities and healthy fermentations. Depending on the individual batch, your system and gear, personal preference, or the manufacturer’s directions, you may have some options to consider for when and how to add nutrient.
Add to Starter Wort
In my opinion, a yeast starter is never a bad idea for homebrewers, and adding nutrient to a starter is also never a bad idea — it helps revive cells depleted by time in storage or by shipping conditions, and ensures the health and viability of the culture going into those crucial first hours of a fermentation.
Whether you can starter wort in a pressure cooker ahead of time to stockpile, or prepare it flask by flask as needed, adding nutrient is as simple as dosing it out alongside the malt extract – adjust nutrient dose as per manufacturer’s or supplier’s instructions.
Add During Boil
This is probably the most common technique, and arguably the easiest for dosing an entire brew length – just add the required amount of nutrient to the wort in the kettle, as per the manufacturer’s instructions. Nutrient additions are typically done near the end of the boil — usually during the last 10 or 15 minutes. If using a nutrient in powder form, it may be beneficial to dissolve it in warm water first.
Remember chelation — some zinc will be lost to break material, so the usable amount delivered to the fermenter will be somewhat less than what went into the boil. It may take a bit of trial-and-error to fine-tune the dosage, but bear this in mind, citizens: discretion is still the better part of nutrient additions. Too much of a good thing can lead to as many problems as not enough.
Add Post-Boil
It’s certainly possible to add nutrients to wort post-boil: ideally at the same time as the yeast is pitched, although obviously that won’t be an option if trying to kickstart a sluggish or stuck fermentation that is already underway.
An advantage to post-boil additions of nutrient is that it helps minimize zinc loss to chelation, since the conditions for zinc chelation are most favorable in the boiler, before the break material is separated.
The challenge of post-boil additions is ensuring the dose is thoroughly diffused into the wort while timing and executing the addition without increasing the risk of unwanted oxygen pickup — not as much of a concern if nutrients are added right away along with the yeast, but a bit more complicated if the fermentation is in progress.
For purposes of even distribution throughout the fermenter, it’s advisable to dissolve the nutrient dose in warm water before gently stirring it in — but refer to the manufacturer’s instructions, which may override that rule of thumb. If you’re concerned about sanitation, a brief boil may not be out of order.
Breakfast, as many nutritionists have said, truly is the most important meal of the day; it’s our first, best, and possibly only chance for vital macronutrients like bacon, pancakes, and coffee. And, if you’re like me, you know how difficult it can be to carry out basic functions in an environment deficient in one or a combination of these vital macronutrients.
As brewers, we’re stewards of the yeast cells in our care, and it would be against their best interests to send them off to the carboy or bucket without a well-rounded and balanced diet, the microbiological equivalent of Kellogg’s Product 19.
Know Your Nutrients Field Guide to Nutrient Blends
A brief primer for the lay homebrewer on what’s in the wort and what it does:
Calcium: Perhaps better known as a mash additive for pH adjustment and enzyme performance, its role in the fermenter is as an aid to yeast flocculation, but too much (over 250 ppm) can inhibit cell growth and fermentation.
Copper: Trace amounts (in Principles of Brewing Science, Fix lists 0.01 ppm) are necessary for cell growth and function; but at too high a concentration it becomes toxic to cells. Primarily finds its way into wort through a brewery’s water source.
Iron: As with copper, trace amounts (0.075 ppm, as per Fix) are beneficial for viability and too much becomes toxic. As with copper, brewing water is the primary contributor.
Magnesium: A critical factor in the complex reactions of yeast metabolism; an excess of Mg can cause unpleasant flavors in the finished beer (and a laxative effect on the drinker). All-malt worts generally supply adequate magnesium for yeast function, but high levels of calcium can limit its availability even if present.
Nitrogen: Essential for yeast nutrition and a proper fermentation. Malt is a rich source of organic nitrogen in the form of amino acids, but as the malt load decreases (whether in a low-gravity all-malt wort, or a wort of any gravity with a malt bill diluted by unmalted adjuncts) so does the amount of nitrogen available to cells, which inhibits growth and disrupts fermentation.
Phosphate: A building block of DNA as well as cell membranes, and also important as a component of adenosine triphosphate (ATP), the primary source of energy in cells. Phosphate is prevalent in malt, but worts with sugars and adjuncts may be phosphate-poor, which can limit cell reproduction and lead to stalled or incomplete fermentations.
Potassium: Another ion with significance for metabolizing wort sugars and other cell processes, but it can actually inhibit yeast metabolism in excess quantities.
Zinc: Vitally important for cell reproduction and conversion of wort sugars to alcohol at trace levels of 0.1-0.5 ppm; higher concentrations become toxic to yeast. Levels can and will be reduced through chelation in the boiler.
Yeast Nutrients at your local homebrew shop
There are a number of nutrient blends, both generic and name brand, with different formulations and applications available to homebrewers today. Since everyone’s wort compositions, yeast strain selection, fermentation conditions, and brewhouses will be a little bit different, the common wisdom is to find one that works for you at the right dosage and stick with it.
Brewer’s Choice Yeast Nutrient
Wyeast Laboratories
A blend of vitamins, minerals, inorganic nitrogen, organic nitrogen, zinc, phosphates and other trace elements that will benefit yeast growth and complete fermentation. Additional nutrients are most valuable during yeast propagation and sluggish or stuck fermentations. Supplementing with nutrients will reduce lag time, improve viability and provide consistent attenuation rates.
Usage: 1⁄2 tsp (2.2 Grams) per 5 gallons (19 L) of wort. Dissolve in warm water. Add solution to kettle 10-15 minutes prior to end of boil.
Fermax
BSG HandCraft
A balanced blend of minerals, proteins, amino acids and vitamins to improve yeast activity during fermentation. Improves attenuation and speed of fermentation. Use 1 teaspoon per gallon prior to fermentation beginning.
Servomyces
White Labs
Servomyces is a nutritional yeast supplement (GMO free) that was originally developed by Weihenstephan and Munich University. It conforms to the restrictions of Reinheitsgebot. Servomyces enables any yeast strain’s ability to incorporate essential nutrients into its cellular structure.
Usage: Add 1 capsule 10 minutes prior to the end of the boil. OR, If your fermentation does not require a boil, open the capsule and pour in the Servomyces, since the capsule requires boiling to melt.
Yeast Nutrient
LD Carlson
A mixture of diammonium phosphate and food-grade urea that nourishes yeast, ensuring that it remains healthy throughout fermentation. One teaspoon per gallon (3.8 L) is recommended.
