Phosphates
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During mashing, phosphatases (enzymes) release a portion of the organically-bound phosphates into the mash. Phosphates provide phosphorus, which is essential for fermentation—phosphorus is a basic requirement for life. The release of phosphates process also alters the pH since they interact with other water minerals.[1][2]
Malted barley contains about 1% by weight of phosphate. It is primarily bound up as malt phytin, which is a mixed potassium and magnesium salt of phytic acid. There's an enzyme called phytase, which helps liberate phosphate. This enzyme is destroyed during kilning in all but the lightest malts.[3] Malt phosphates react with dissolved calcium to precipitate calcium phosphate, releasing hydrogen ions that react with dissolved carbonates, which reduces alkalinity and lowers the pH. (This book shows the chemical reaction...) The reduction of alkalinity is limited by the amount of calcium present in the mash/water.
There are regulatory limits on the concentration of phosphate phosphorus that may be present in potable water, and a suggested maximum in brewing liquor is 1 mg/litre. Most of the phosphate in beer is derived from malt, although phosphoric acid or acid phosphate salts may be used to adjust the pH or to release carbon dioxide from bicarbonate-rich waters. Worts can also contain the organic phosphate phytate (salts of phytic acid), derived from malt. Phosphates are important pH buffers in brewing and interactions between calcium ions and phosphates, and other substances, usefully reduce the pH in mashing and during the hop-boil. Phosphoric acid is also used for acid-washing yeasts.[4]
Little phosphate comes from the brewing liquor, except where phosphoric acid or acid phosphate salts have been used for pH adjustment.[4]
High levels of phosphate (both inorganic and organic) are derived from malt.16 Phosphate is essential to yeast cells and has many roles, including its incorporation into structural molecules, such as phospholipids and phosphomannans, and for the formation of nucleic acids (DNA, RNA) and phosphorylated metabolites, such as adenosine triphosphate (ATP) and glucose-6-phosphate.23[5]
The acidic phosphatases occurring in the malt break down the organic phosphates in the malt, releasing phosphoric acid which further dissociates into primary phosphates and hydrogen ions. This results in an increase in the mash acidity, i.e. a lowering of the pH and thus an increase in the buffering in the mash, wort and beer. The optimum effect of these enzymes results in summary at a pH of 5.0 and a temperature between 50 and 53°C. Nevertheless, these enzymes are still effective at higher temperatures, because every rest (at 50, 62, 65 and even at 70°C) increases the buffering.[6] see brewing pH
combination of mashing-in temperature of 63–65°C and pH 5.2 can influence the production of phosphates and the accompanying buffering capacity of the wort. Too high buffering capacity of wort makes it difficult to end with an opti- mal beer pH between 4.2–4.5 after fermentation. Beer pH should be in this range in order to avoid problems with flavor stability, colloidal stability, foam stability, and the taste of the fresh beer (5). Phosphate content can be influenced by phytase activity dur- ing mashing. Two phytase enzymes are characterized in barley malt (17). Phytase 1 is produced during germination; phytase 2 is already present in the barley. The pH optima for phytases 1 and 2 are 5.0 and 6.0, respectively. The optimum temperatures for phytases 1 and 2 are 45°C and 55°C, respectively (17). After 30 min at 70°C, phytase is completely inactivated (23). The phytase activity is on average 6 times higher after 5 days of germination compared with the barley. After kilning, about 25% of this activ- ity remains in the malt (23). Fig. 5 shows the influence of temperature and pH at mashing-in on the phosphate content and on the final pH after fermentation. Mashing-in at pH of 5.2 gives rise to a significantly higher con- centration of phosphates in the wort and a significantly higher pH after fermentation. Furthermore, a higher mashing-in temperature results in significantly lower amounts of phosphates and a lower pH after fermentation. However, when mashing-in at 45°C and pH 5.5, the phosphate concentration and the pH after fermentation is rather similar to the mashing-in at higher temperature and at a decreased pH.[7]
Phosphates occur in the structures of many compounds in barley grains (e.g. in phytin, nucleic acids, coenzymes, proteins, etc.). They are released from these compounds in reactions occurring during malting and brewing. Most of the phosphates are bound in phytin that is salts of the organic acid myoinositol hexakis – (dihydrogen phosphate). Phytin is hydrolyzed in the mash tun releasing inorganic phosphate and the B vitamin, myoinosital (deLange, 2004). The amount of phosphate in malt is as much as 1% of its weight (as P 2 O3 ) according to Briggs et al. (1981) . The term phosphate refers to compounds that involve the ions of phosphoric acid. Phosphates react with calcium and magnesium as reported earlier. The presence of phosphate is extremely important for fermentation. Phosphorus is required for the formation of ATP, the formation of the phospholipid double membrane around the yeast cell and buffering against pH shift. A deficiency of phosphates causes fermentation problems and reduction in cell growth (Kunze, 2004).[8]
References[edit]
- ↑ Kunze W. Wort production. In: Hendel O, ed. Technology Brewing & Malting. 6th ed. VBL Berlin; 2019.
- ↑ Krottenthaler M, Back W, Zarnkow M. Wort production. In: Esslinger HM, ed. Handbook of Brewing: Processes, Technology, Markets. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2009.
- ↑ Palmer J, Kaminski C. Water: A Comprehensive Guide for Brewers. Brewers Publications; 2013.
- ↑ a b Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ Taylor DG. Water. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
- ↑ Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
- ↑ De Rouck G, Jaskula B, De Causmaecker B, et al. The influence of very thick and fast mashing conditions on wort composition. J Am Soc Brew Chem. 2013;71(1):1–14.
- ↑ 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.