Yeast has a complex nutritional requirement. Conversion of wort sugar to alcohol is not just one chemical reaction. Hundreds of chemical reactions occur inside a yeast cell. A yeast cell can be thought of as a “bag of enzymes”.
Each enzyme catalyzes a different chemical reaction. Each enzyme also has specific mineral requirements for optimum performance. These chemical reactions produce alcohol, flavor compounds, energy for growth, cell wall compounds, and so on. If any of these reactions are compromised, there can be an effect on yeast health and fermentation performance, which has a direct impact on flavor.
Zinc is important in the cell cycle (reproduction), and is a cofactor for alcohol dehydrogenase, the enzyme responsible for alcohol production. Other metal ions can not substitute in place of zinc. Supplementation of zinc into brewers' wort generally has the effect of speeding up beer fermentation timelines, as well as preventing stuck fermentations.
The zinc requirement in beer fermentation can vary depending on the yeast strain, the type of beer being produced, and the composition of the wort. A typical requirement for yeast growth during beer fermentation is between 0.15 to 0.5 mg/L(ppm) of zinc.
If the zinc levels are too low, yeast growth and fermentation can be negatively impacted, resulting in slower fermentation, incomplete attenuation, and undesirable flavor compounds. On the other hand, excessive levels of zinc can lead to yeast stress and inhibition of fermentation leading to off-flavors in the beer.
A key consideration when adding minerals is when they are added during the fermentation process. When the wort composition of minerals is technically sufficient, the bio-availability to yeast cells is in question. If added too early on the hot side, they can bind to trub and chelate or drop out of solution. Even when metals successfully enter yeast cells, they can be chelated within the cytoplasm. This is actually a natural defense mechanism for yeast, and is helpful for brewers to keep toxic metals from hurting fermentations.
Brewers can supplement the zinc levels in their wort by using zinc-rich brewing salts, such as zinc sulfate, or by adding nutrient blends that contain zinc, such as Servomyces.
Our product, Servomyces, is an organic yeast nutrient that contains naturally zinc-enriched yeast hulls.
Dosage Rate: 1 g Servomyces is used for 100 liters of wort for fermentation
Servomyces is an effective delivery method for zinc, and is produced in a patented process by which brewers yeast is grown in the presence of metal ions, including zinc and magnesium, and then dried and killed. When added to brewery fermentations in very minute quantities, the effect is dramatic to fermentation speed and to yeast performance/viability. The effect is much greater than with the addition of the same quantity of zinc salts. Fluorescent tests show that most of the minerals are bound within the cell wall of Servomyces (Fig.3), which may aid in preventing them from being chelated in the wort.
A B
Fig. 3
A Servomyces (Inactivated) stained with 5μM Newport Green Diacetate
B Inactivated Yeast supplemented with 1M ZnSO4.7H2O and stained with 5μM Newport Green Diacetate
The images were prepared in the laboratory of Dr. Graeme Walker, the University of Abertay, Scotland.
Permission to publish these images is gratefully acknowledged2.
We highly recommend to still add Servomyces at 5-10 minutes before the end of boil or during the whirlpool. Adding it later ensures proper zinc levels are met, as well as allowing enough time for the product to dissolve and homogenize.
Servomyces is yeast grown in the presence of high concentrations of zinc. The yeast is then killed, and the zinc that is incorporated into the yeast cell walls is transferred to your yeast effectively. Servomyces can also be used at the end of the boil because the cells protect the zinc from being attracted to the hot break trub.
Servomyces Zinc Concentration: 50,000 ppm zinc
Dosage rate: 1 g/HL
This achieves 0.5 ppm zinc in your yeast.
Zinc Buddy™ is pre-sterilized and can be pitched directly to the cold side. With Servomyces, getting the nutrient in solution can be troublesome so we recommend adding it to the whirlpool or 5-10 minutes end of boil.
Zinc Buddy™ is an alternative if you are not already using Servomyces, providing you with an additional 0.2ppm zinc, for a total of 0.3ppm in wort. Servomyces can be used at higher concentrations than mineral zinc (0.5ppm vs. 0.2ppm), this is why Servomyces gives you the best results. Mineral zinc at higher concentrations can sometimes lead to off-flavors.
Brewers can produce great-tasting beers with optimal flavor, aroma, and alcohol content in a quick and timely manner. All that’s needed is to add some zinc; try adding it to your next brew today and tell us about your results!
References:
1.. Mclaren, J.I., et al., Zinc Problem Solved? Brauwelt International- No.1/2001, V. 19, pgs. 60-63, 2001
2. Walker, G.M., Role of Metal Ions in Brewing Yeast Fermentation Performance. Brewing Yeast
Fermentation Performance, Blackwell Science Ltd., pgs.86-91, 2000.
3. Oaveloose, Marvin. "An Investigation of Zinc Concentrations in Brewhouse Worts". MBAA Technical Quarterly, Vol. 24, ppl09-112, 1987
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