Magnesium

From Brewing Forward
Magnesium periodic table emblem

Magnesium (Mg2+) is a mineral naturally present in water and grain. It is one of the most important ions for fermentation performance.[1][2][3] Magnesium is required for the function of over 300 enzymes, making it a necessary nutrient for yeast growth and fermentation.[4][5][6][7] Magnesium is also an important component of beer flavor, imparting a lightly sour and astringent or bitter character. However, as the level of magnesium increases, the flavor may become unpleasant. At excessive levels (higher than 125 mg/L in beer), magnesium can have possible diuretic or laxative effects, although the latter is unlikely.[8][9] To avoid any negative effects, it is suggested to have no more than 20–40 mg/L magnesium in the brewing water.[10][9][8] The presence of some magnesium in the brewing water is widely considered to be beneficial, although there is no consensus on the ideal amount.[8][11] Magnesium behaves similarly to calcium, and the effects of these two ions have some interesting interactions.[8] Magnesium is classified as an alkaline-earth metal.

Beer magnesium content: Almost all of the magnesium from the ingredients will be present in the final beer, as only a relatively small amount is taken up by the yeast. Standard strength commercial beers contain magnesium concentrations from around 60 to 150 mg/L.[12]

Potential sources of magnesium[edit]

The magnesium content in beer comes from the raw ingredients, mainly the water and grist, plus any salts added by the brewer.

  • Brewing water - The water used to make beer may contain dissolved magnesium. North American municipal tap water typically contains 0–48 mg/L magnesium, with an average around 8–12 mg/L.[13][14][15] Ground water tends to have higher magnesium than surface water. American bottled waters contain 0–95 mg/L, although the average is very low at 3–8 m/L. European bottled water contains higher magnesium levels. Note that some tap water and some bottle waters exceed the recommended level of magnesium, making them unsuitable for brewing.
  • Grain - Magnesium has high extractability compared to that of other metals, up to 80%.[1] A typical wort provides around 50–90 mg/L magnesium extracted from the grain.[1][8][16] However, a large portion of the measured magnesium may be bound to organic molecules, which greatly reduces the amount available to the yeast (grain-extracted magnesium has low bioavailablility).[5][4] The magnesium content of grain can vary widely, probably due to fertilizer usage.[12]
  • Salt additives - Brewers can enrich the magnesium level of the wort by adding brewing salts that contain magnesiumm, such as magnesium chloride or magnesium sulfate. Magnesium added from these salts will increase the amount available to be taken up by the yeast.

Effects of magnesium[edit]

In the context of brewing beer, magnesium has several important effects.

  • Improved pH control - Magnesium beneficially lowers the pH during mashing by precipitating with phosphates, proteins, and other compounds, although not as effectively as calcium because magnesium salts are much more soluble.[9][17][18][9][8]
  • Increased Maillard reactions - Magnesium promotes Maillard reactions between sugars and amino acids, which may or may not visibly increase beer color or have an impact on flavor (this has not been well studied).[12]
  • Improved fermentation - Magnesium ions are needed by many yeast enzymes, such as pyruvate decarboxylase.[4][9][8][17][1] In fact, magnesium is required for yeast growth and metabolism (fermentation).[1][5][17][19] The magnesium extracted from grain typically provides the minimum amount of magnesium needed to support fermentation, although the level is usually not optimal.[1][8][4][20] Additional magnesium can sometimes improve fermentation rate, including faster onset of fermentation, and can sometimes help improve yeast ethanol tolerance and improve the ability of yeast to ferment under stressful conditions, increasing sugar uptake and alcohol production.[10][4][1][5][21][22] Calcium ions inhibit magnesium absorption by the yeast,[1] and therefore magnesium addition may be especially useful in wort with a high calcium level (e.g. from the water or calcium salt additions).[5] Note that the response is strain-dependent.[5][6][21]
  • Improved yeast flocculation - Magnesium ions can positively influence flocculation, substituting for calcium.[1] This effect can be inhibited by the presence of metal-chelating agents (i.e. tannin additives) since magnesium is more sensitive to chelation than calcium.
  • Flavor - At the moderate levels typically found in wort, magnesium can enhance a beer's character by providing a mild sour or bitter astringency.[8][23][17][9][24][11] At excessive levels, the sour and bitter notes can become unpleasant and harsh.[8][25] These flavor effects appear to depend on a balance between the magnesium and calcium ions, since calcium can reduce the flavor impact of magnesium.[17]
  • Increased hop utilization - Magnesium increases humulone isomerization, which may contribute to its perceived bitter flavor effect.[12]

How to adjust the magnesium level[edit]

In order to ensure a good fermentation, the presence of some magnesium in brewing water is recommended.[10] While magnesium sulfate (e.g. Epsom salt) is a common traditional option, magnesium chloride is also a good option for adding magnesium if you would prefer to minimize the amount of sulfate. Magnesium content in yeast extracts (i.e. yeast nutrient products) can also improve the fermentation performance of yeast, although adding a magnesium salt might be more beneficial.[1] When considering the potential of magnesium to improve yeast fermentation performance, the concentration of wort calcium should also be taken into account.[1] Calcium competes with magnesium for uptake by the yeast, and any observed improvement may be related to the Mg:Ca ratio rather than the absolute concentration of magnesium.[1][5] See Water for our guide to adjusting water minerals and mash pH.

If the magnesium level in your tap water is too high, the only method to decrease the level is to purify the water with a reverse osmosis system. Yeast can theoretically absorb a maximum of 30–45 mg/L of magnesium during a typical fermentation, only mildly lowering the amount in the final beer.[4]

See also[edit]

References[edit]

  1. ↑ a b c d e f g h i j k l Gibson BR. 125th anniversary review: improvement of higher gravity brewery fermentation via wort enrichment and supplementation. J Inst Brew. 2011;117(3):268–284.
  2. ↑ Walker G, De Nicola R, Anthony S, Learmonth R. Yeast-metal interactions: impact on brewing and distilling fermentations. In: Proceedings of the Institute of Brewing & Distilling Asia Pacific Section 2006 Convention. 2006.
  3. ↑ Montanari L, Mayer H, Marconi O, Fantozzi P. Chapter 34: Minerals in beer. In: Preedy VR, ed. Beer in Health and Disease Prevention. Academic Press; 2009:359–365.
  4. ↑ a b c d e f Saltukoglu A, Slaughter JC. The effect of magnesium and calcium on yeast growth. J Inst Brew. 1983;89(2):81–83.
  5. ↑ a b c d e f g Walker GM, Birch RM, Chandrasena G, Maynard AI. Magnesium, calcium, and fermentative metabolism in industrial yeasts. J Am Soc Brew Chem. 1996;54(1):13–18.
  6. ↑ a b Rees EM, Stewart GG. The effects of increased magnesium and calcium concentrations on yeast fermentation performance in high gravity worts. J Inst Brew. 1997;103(5):287–291.
  7. ↑ Kordialik‐Bogacka E, Bogdan P, Ciosek A. Effects of quinoa and amaranth on zinc, magnesium and calcium content in beer wort. Int J Food Sci Technol. 2019;54(5):1706–1712.
  8. ↑ a b c d e f g h i j Palmer J, Kaminski C. Water: A Comprehensive Guide for Brewers. Brewers Publications; 2013.
  9. ↑ a b c d e f Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  10. ↑ a b c Ryder DS. Processing aids in brewing. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  11. ↑ a b Comrie AA. Brewing liquor—a review. J Inst Brew. 1967;73(4):335–346.
  12. ↑ a b c d Omari IO, Charnock HM, Fugina AL, Thomson EL, McIndoe JS. Magnesium-accelerated Maillard reactions drive differences in adjunct and all-malt brewing. J Am Soc Brew Chem. 2021;79(2):145–155.
  13. ↑ Azoulay A, Garzon P, Eisenberg MJ. Comparison of the mineral content of tap water and bottled waters. J Gen Intern Med. 2001;16(3):168–175.
  14. ↑ Tackaberry R. Mineral content of drinking water, 100 USA cities. The Magnesium Web Site. 2002. Accessed online April 2024.
  15. ↑ Burlingame GA, Dietrich AM, Whelton AJ. Understanding the basics of tap water taste. J Am Water Works Assoc. 2007;99(5):100–111.
  16. ↑ Holzmann A, Piendl A. Malt modification and mashing conditions as factors influencing the minerals of wort. J Am Soc Brew Chem. 1977;35(1):1–8.
  17. ↑ a b c d e Taylor DG. Water. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  18. ↑ Eumann M, Schildbach S. 125th anniversary review: Water sources and treatment in brewing. J Inst Brew. 2012;118:12–21.
  19. ↑ White C. Yeast nutrients make fermentations better. White Labs. Accessed 2020.
  20. ↑ Walker GM. Role of metal ions in brewing yeast fermentation performance. In: Smart KA, ed. Brewing Yeast Fermentation Performance. 1st ed. Wiley-Blackwell; 2000:86–91.
  21. ↑ a b Bromberg SK, Bower PA, Duncombe GR, et al. Requirements for zinc, manganese, calcium, and magnesium in wort. J Am Soc Brew Chem. 1997;55(3):123–128.
  22. ↑ Walker GM. Magnesium as a stress-protectant for industrial strains of Saccharomyces cerevisiae. J Am Soc Brew Chem. 1998;56(3):109–113.
  23. ↑ Howe S. Raw materials. In: Smart C, ed. The Craft Brewing Handbook. Woodhead Publishing; 2019.
  24. ↑ Habschied K, Košir IJ, Krstanović V, Kumrić G, Mastanjević K. Beer polyphenols—bitterness, astringency, and off-flavors. Beverages. 2021;7(2):38.
  25. ↑ Fix G. Principles of Brewing Science. 2nd ed, Brewers Publications; 1999.
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