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Worts that are prepared with reasonable percentages of malt tend to be rich in amino acids. Low FAN levels are undesirable in wort. The traditional rule is that serious problems (long lags, high diacetyl, etc) can result from FAN below 150-175ppm. A 12°P malt wort will typically have 225-275ppm FAN, which is ideal.<ref name=fix>Fix, George. ''Principles of Brewing Science.'' 2nd ed., Brewers Publications, 1999.</ref> As a general rule, it is usually desirable to keep FAN levels below 350ppm, something that can be achieved with a suitable [[mashing]] schedule. | Worts that are prepared with reasonable percentages of malt tend to be rich in amino acids. Low FAN levels are undesirable in wort. The traditional rule is that serious problems (long lags, high diacetyl, etc) can result from FAN below 150-175ppm. A 12°P malt wort will typically have 225-275ppm FAN, which is ideal.<ref name=fix>Fix, George. ''Principles of Brewing Science.'' 2nd ed., Brewers Publications, 1999.</ref> As a general rule, it is usually desirable to keep FAN levels below 350ppm, something that can be achieved with a suitable [[mashing]] schedule. | ||
In worts from all-malt mashes the levels of amino acids are nearly always adequate for good yeast growth. However, in worts made using mash tun and/or copper adjuncts the FAN levels may fall below the 100–140 mg/litre level, which is regarded as the minimum needed for trouble-free fermentations.<ref name=bsp/> | |||
Too much or too little FAN can increase diacetyl production during fermentation.<ref name=fix/> | Too much or too little FAN can increase diacetyl production during fermentation.<ref name=fix/> | ||