Free amino nitrogen
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Free amino nitrogen (FAN) is a measure of the low molecular weight substances, mainly amino acids, which are needed to support yeast growth and metabolism.[1] FAN has long been regarded as a predictor of healthy yeast growth, viability, vitality, fermentation efficiency, and beverage quality and flavor stability.[2] This is because FAN is used to provide not only nitrogen to the yeast cells for growth but also the wort nitrogen content or its metabolic products which affect flavor compounds. In beer, FAN is the product of protein degradation occuring from enzyme activity from the grain used, such as malted barley.[2]
Wort FAN is affected by the malt/adjunct ratio, the mashing schedule, barley variety, barley growth conditions, and various malting parameters.[2] Around 88% of the total yeast utilizable nitrogen is produced during malting and 12% is produced during mashing (on average, with some variation between malts).[2][3] This means that brewers producing all-malt wort generally don't need to worry about supplementing yeast nutrition as long as good practices are used for brewing and pitching. The FAN level of wort is typically adequate (when produced within the standard pH range, which is optimal for FAN production) regardless of whether a protein rest is performed.[4][5][6][7][3]
Optimal wort FAN levels differ from fermentation to fermentation and from yeast strain to yeast strain.[2] Thus, they are considered controversial and are simply general guidelines.[2] Furthermore, the optimum FAN values change with different wort sugar levels.[2] The minimal wort FAN level to achieve satisfactory yeast growth and fermentation performance in normal gravity wort fermentations (12°P) is 130 mg/L but, for rapid attenuation resulting in higher ethanol production, increased levels of wort FAN are required (150–190 mg/L).[2][8] Other sources suggest desired FAN concentration as high as 200–250 mg/L free amino acids.[5] However, wort with excessive FAN may cause too much ester production by the yeast.[8]
The amount of FAN can be approximately measured by using a formol titration (designated as Formol-N), if desired.[9][1] See YAN testing.
Excessive FAN can cause a butterscotch off-flavor.[10] Cites: Bokulich NA, Bamforth CW (2013) The microbiology of malting and brewing. Microbiol Mol Biol R 77:157–172
For Pro to be absorbed by yeasts, a mitochondrial oxidase, which is inactive under anaerobic conditions, is required. Making it the less absorbable AA, explaining why it is normally present in higher amounts in beers when compared to other AA[11]
A lower FAN content is advantageous for flavour stability, owing to the lower level of precursors for the generation of Strecker aldehydes during beer aging.[12]
See also[edit]
References[edit]
- ↑ a b Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ a b c d e f g h Lekkas C, Hill AE, Stewart GG. Extraction of FAN from malting barley during malting and mashing. J Am Soc Brew Chem. 2014;72(1):6–11.
- ↑ a b Evans E. Mashing. American Society of Brewing Chemists and Master Brewers Association of the Americas; 2021.
- ↑ 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.
- ↑ a b Kühbeck F, Dickel T, Krottenthaler M, et al. Effects of mashing parameters on mash β-glucan, FAN and soluble extract levels. J Inst Brew. 2005;111(3):316–327.
- ↑ Schwarz KJ, Boitz LI, Methner FJ. Release of phenolic acids and amino acids during mashing dependent on temperature, pH, time, and raw materials. J Am Soc Brew Chem. 2012;70(4):290–295.
- ↑ Evans DE, Goldsmith M, Redd KS, Nischwitz R, Lentini A. Impact of mashing conditions on extract, its fermentability, and the levels of wort free amino nitrogen (FAN), β-glucan, and lipids. J Am Soc Brew Chem. 2012;70(1):39–49.
- ↑ a b Cvengroschová M, Šepel'ová G, Šmogrovičová D. Effect of mashing-in temperature on free amino nitrogen concentration and foam stability of beer. Monatsschrift Brauwiss. 2003;56(7/8):128–131.
- ↑ Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
- ↑ Liguori L, De Francesco G, Orilio P, Perretti G, Albanese D. Influence of malt composition on the quality of a top fermented beer. J Food Sci Technol. 2021;58:2295–2303.
- ↑ Baigts-Allende DK, Perez-Alva A, Ramirez-Rodrigues MA, Palacios A, Ramirez-Rodrigues MM. A comparative study of polyphenolic and amino acid profiles of commercial fruit beers. J Food Compos Anal. 2021;100:103921.
- ↑ Kunz T, Müller C, Mato‐Gonzales D, Methner FJ. The influence of unmalted barley on the oxidative stability of wort and beer. J Inst Brew. 2012;118(1):32–39.